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• Search engine solution for Django that actually works?

  - by prometheus

  The story so far: Decided to go with Xapian as search backend because it has all search-engine features I was looking for, knows about Unicode, stemming, has few dependencies and requires no bloated app-server installation on top of it. Tried Django and Haystack (plus xapian-haystack, the backend glue code to tie Haystack to Xapian) because it was advertised on quite some blogs as "working". Did not work. Neither django-haystack nor the xapian-haystack project provide a version combination that actually works together. MASTER from both projects yields an error from Xapian, so it's not stable at all. Haystack 1.0.1 and xapian-haystack 1.0.x/1.1.0 are not API-compatible. Plus, in a minimally working installation of Haystack 1.0.1 and xapian-haystack MASTER, any complex query yields zero results due to errors in either django-haystack or xapian-haystack (I double-verified this), maybe because the unit-tests actually test very simple cases, and no edge-cases at all. Tried Djapian. The source-code is riddled with spelling errors (mind you, in variable names, not comments), documentation is also riddled with ambiguities and outdated information that will never lead to a working installation. Not surprisingly, users rarely ask for features but how to get it working in the first place. Next on the plate: exploring Solr (installing a Java environment plus Tomcat gives me headaches, the machine is RAM- and CPU-constrained), or Lucene (slightly less headaches, but still). Before I proceed spending more time with a solution that might or might not work as advertised, I'd like to know: Did anyone ever get an actual, real-world search solution working in Django? I'm serious. I find it really frustrating reading about "large problems mostly solved", and then realizing that you will never get a working installation from the source-code because, actually, all bloggers dealing with those "mostly solved problems" never went past basic installation and copy-pasting the official tutorials. So here are the requirements: must be able to search for 10-100 terms in one query must handle + (term must be present) and - (term must not be present), AND/OR must handle arbitrary grouping (i.e. parentheses around AND/OR) must allow for Django-ORM filtering before or after fulltext-search (i.e. pre-/post-processing of results with the full set of filters that Django knows about) alternatively, there must be a facility to bulk-fetch the result set and transform it into a QuerySet should be light on the machine, so preferably no humongous JVM and Java-based app-server installation Is there anything out there that does this? I'm not interested in anecdotal evidence, or references to some blog posts that claim it should be working. I'd like to hear from someone who actually has a fully-functional setup working in the real world, under real conditions, with real queries. EDIT: Let me repeat again that I'm not so much interested in anecdotal evidence that someone, somewhere has a somewhat running installation working with unspecified properties. I already went there, I read all the blog posts, mailing lists, I contacted the authors, but when it came to actual implementation of real-world scenarios, nothing ever worked as advertised. Also, and a user below brought that point up as well, considering the TCO of any project, I'm definitely not interested in hearing that someone, somewhere was able to pull it off once a vendor parachuted in an unknown number of specialists to monkey-patch the whole installation with specific domain-knowledge that's documented nowhere. So, please, if you claim you have a working installation that actually satisfies minimum requirements for a full-fledged search (see requirements above), please provide the following so that we can all benefit from a search solution for Django that actually solves the problem: exact Linux distribution, release version, exact release version of Haystack (or equivalent) and release version of search backend, exact release version of the search engine publicly (!) available documentation how to set up all components exactly in the way that your installation was set up such that the minimal requirements above are met. Thank you.

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• Search engine solution for Django that actually works?

  - by prometheus

  The story so far: Decided to go with Xapian as search backend because it has all search-engine features I was looking for, knows about Unicode, stemming, has few dependencies and requires no bloated app-server installation on top of it. Tried Django and Haystack (plus xapian-haystack, the backend glue code to tie Haystack to Xapian) because it was advertised on quite some blogs as "working". Did not work. Neither django-haystack nor the xapian-haystack project provide a version combination that actually works together. MASTER from both projects yields an error from Xapian, so it's not stable at all. Haystack 1.0.1 and xapian-haystack 1.0.x/1.1.0 are not API-compatible. Plus, in a minimally working installation of Haystack 1.0.1 and xapian-haystack MASTER, any complex query yields zero results due to errors in either django-haystack or xapian-haystack (I double-verified this), maybe because the unit-tests actually test very simple cases, and no edge-cases at all. Tried Djapian. The source-code is riddled with spelling errors (mind you, in variable names, not comments), documentation is also riddled with ambiguities and outdated information that will never lead to a working installation. Not surprisingly, users rarely ask for features but how to get it working in the first place. Next on the plate: exploring Solr (installing a Java environment plus Tomcat gives me headaches, the machine is RAM- and CPU-constrained), or Lucene (slightly less headaches, but still). Before I proceed spending more time with a solution that might or might not work as advertised, I'd like to know: Did anyone ever get an actual, real-world search solution working in Django? I'm serious. I find it really frustrating reading about "large problems mostly solved", and then realizing that you will never get a working installation from the source-code because, actually, all bloggers dealing with those "mostly solved problems" never went past basic installation and copy-pasting the official tutorials. So here are the requirements: must be able to search for 10-100 terms in one query must handle + (term must be present) and - (term must not be present), AND/OR must handle arbitrary grouping (i.e. parentheses around AND/OR) must allow for Django-ORM filtering before or after fulltext-search (i.e. pre-/post-processing of results with the full set of filters that Django knows about) alternatively, there must be a facility to bulk-fetch the result set and transform it into a QuerySet should be light on the machine, so preferably no humongous JVM and Java-based app-server installation Is there anything out there that does this? I'm not interested in anecdotal evidence, or references to some blog posts that claim it should be working. I'd like to hear from someone who actually has a fully-functional setup working in the real world, under real conditions, with real queries. EDIT: Let me repeat again that I'm not so much interested in anecdotal evidence that someone, somewhere has a somewhat running installation working with unspecified properties. I already went there, I read all the blog posts, mailing lists, I contacted the authors, but when it came to actual implementation of real-world scenarios, nothing ever worked as advertised. Also, and a user below brought that point up as well, considering the TCO of any project, I'm definitely not interested in hearing that someone, somewhere was able to pull it off once a vendor parachuted in an unknown number of specialists to monkey-patch the whole installation with specific domain-knowledge that's documented nowhere. So, please, if you claim you have a working installation that actually satisfies minimum requirements for a full-fledged search (see requirements above), please provide the following so that we can all benefit from a search solution for Django that actually solves the problem: exact Linux distribution, release version, exact release version of Haystack (or equivalent) and release version of search backend, exact release version of the search engine publicly (!) available documentation how to set up all components exactly in the way that your installation was set up such that the minimal requirements above are met. Thank you.

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• Android: Use XML Layout for List Cell rather than Java Code Layout (Widgets)

  - by Stephen Finucane

  Hi, I'm in the process of making a music app and I'm currently working on the library functionality. I'm having some problems, however, in working with a list view (In particular, the cells). I'm trying to move from a simple textview layout in each cell that's created within java to one that uses an XML file for layout (Hence keeping the Java file mostly semantic) This is my original code for the cell layout: public View getView(int position, View convertView, ViewGroup parent) { String id = null; TextView tv = new TextView(mContext.getApplicationContext()); if (convertView == null) { music_column_index = musiccursor.getColumnIndexOrThrow(MediaStore.Audio.Media.TITLE); musiccursor.moveToPosition(position); id = musiccursor.getString(music_column_index); music_column_index = musiccursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DISPLAY_NAME); musiccursor.moveToPosition(position); id += "\n" + musiccursor.getString(music_column_index); music_column_index = musiccursor.getColumnIndexOrThrow(MediaStore.Audio.Albums.ALBUM); musiccursor.moveToPosition(position); id += "\n" + musiccursor.getString(music_column_index); tv.setText(id); } else tv = (TextView) convertView; return tv; } And my new version: public View getView(int position, View convertView, ViewGroup parent) { View cellLayout = findViewById(R.id.albums_list_cell); ImageView album_art = (ImageView) findViewById(R.id.album_cover); TextView album_title = (TextView) findViewById(R.id.album_title); TextView artist_title = (TextView) findViewById(R.id.artist_title); if (convertView == null) { music_column_index = musiccursor.getColumnIndexOrThrow(MediaStore.Audio.Albums.ALBUM); musiccursor.moveToPosition(position); album_title.setText(musiccursor.getString(music_column_index)); //music_column_index = musiccursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DISPLAY_NAME); //musiccursor.moveToPosition(position); music_column_index = musiccursor.getColumnIndexOrThrow(MediaStore.Audio.Media.TITLE); musiccursor.moveToPosition(position); artist_title.setText(musiccursor.getString(music_column_index)); } else{ cellLayout = (TextView) convertView; } return cellLayout; } The initialisation (done in the on create file): musiclist = (ListView) findViewById(R.id.PhoneMusicList); musiclist.setAdapter(new MusicAdapter(this)); musiclist.setOnItemClickListener(musicgridlistener); And the respective XML files: (main) <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <ListView android:id="@+id/PhoneMusicList" android:layout_width="fill_parent" android:layout_height="fill_parent" /> <TextView android:id="@android:id/empty" android:layout_width="wrap_content" android:layout_height="0dip" android:layout_weight="1.0" android:text="@string/no_list_data" /> </LinearLayout> (albums_list_cell) <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/albums_list_cell" android:layout_width="wrap_content" android:layout_height="wrap_content"> <ImageView android:id="@+id/album_cover" android:layout_alignParentLeft="true" android:layout_alignParentTop="true" android:layout_width="50dip" android:layout_height="50dip" /> <TextView android:id="@+id/album_title" android:layout_toRightOf="@+id/album_cover" android:layout_alignParentTop="true" android:layout_width="wrap_content" android:layout_height="wrap_content" /> <TextView android:id="@+id/artist_title" android:layout_toRightOf="@+id/album_cover" android:layout_below="@+id/album_title" android:layout_width="wrap_content" android:layout_height="15dip" /> </RelativeLayout> In theory (based on the tiny bit of Android I've done so far) this should work..it doesn't though. Logcat gives me a null pointer exception at line 96 of the faulty code, which is the album_title.setText line. It could be a problem with my casting but Google tells me this is ok :D Thanks for any help and let me know if you need more info!

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• JAVA BubbleSort Output Plotting

  - by John Smith

  I'm not sure how to plot the output I get with my run time results for BubbleSort. Here's the thing: I've written a working BubbleSort algorithm that does exactly as it should. But I wish to plot the output, to show the following: Best Case, Worst Case, Average Case ... How would I go about plotting it on a graph? Here is the code: public class BubbleSort { static double bestTime = 10000000, worstTime = 0; public static void main(String[] args) { int BubArray[] = new int[]{13981, 6793, 2662, 10986, 733, ... #1000 integers}; System.out.println("Unsorted List Before Bubble Sort"); for(int a = 0; a < BubArray.length; a++){ System.out.print(BubArray[a] + " "); } System.out.println("\n Bubble Sort Execution ..."); for(int i=0; i<10000;i++) { bubbleSortTimeTaken(BubArray, i); } int itrs = bubbleSort(BubArray); System.out.println(""); System.out.println("Array After Bubble Sort"); System.out.println("Moves Taken for Sort : " + itrs + " Moves."); System.out.println("BestTime: " + bestTime + " WorstTime: " + worstTime); System.out.print("Sorted Array: \n"); for(int a = 0; a < BubArray.length; a++){ System.out.print(BubArray[a] + " "); } } private static int bubbleSort(int[] BubArray) { int z = BubArray.length; int temp = 0; int itrs = 0; for(int a = 0; a < z; a++){ for(int x=1; x < (z-a); x++){ if(BubArray[x-1] > BubArray[x]){ temp = BubArray[x-1]; BubArray[x-1] = BubArray[x]; BubArray[x] = temp; } itrs++; } } return itrs; } public static void bubbleSortTimeTaken(int[] BubArray, int n) { long startTime = System.nanoTime(); bubbleSort(BubArray); double timeTaken = (System.nanoTime() - startTime)/1000000d; if (timeTaken > 0) { worstTime = timeTaken; } else if (timeTaken < bestTime) { bestTime = timeTaken; } System.out.println(n + "," + timeTaken); } } The output are as the following ( execution number, time (nano/10^6): Unsorted List Before Bubble Sort 13981 6793 2662 .... #1000 integers Bubble Sort Execution ... 0, 18.319891 1, 4.728978 2, 3.670697 3, 3.648922 4, 4.161576 5, 3.824369 .... 9995, 4.331423 9996, 3.692473 9997, 3.709893 9998, 6.16055 9999, 4.32209 Array After Bubble Sort Moves Taken for Sort : 541320 Moves. BestTime: 1.0E7 WorstTime: 4.32209 Sorted Array: 10 11 17 24 57 60 83 128 141 145 ... #1000 integers I am looking for graphs to represent Average, Best and Worst case based on the output but my current graphs don't look correct. Any help would be appreciated, thanks.

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• Allocation algorithm help, using Python.

  - by Az

  Hi there, I've been working on this general allocation algorithm for students. The pseudocode for it (a Python implementation) is: for a student in a dictionary of students: for student's preference in a set of preferences (ordered from 1 to 10): let temp_project be the first preferred project check if temp_project is available if so, allocate it to them and make the project UNavailable to others Quite simply this will try to allocate projects by starting from their most preferred. The way it works, out of a set of say 100 projects, you list 10 you would want to do. So the 10th project wouldn't be the "least preferred overall" but rather the least preferred in their chosen set, which isn't so bad. Obviously if it can't allocate a project, a student just reverts to the base case which is an allocation of None, with a rank of 11. What I'm doing is calculating the allocation "quality" based on a weighted sum of the ranks. So the lower the numbers (i.e. more highly preferred projects), the better the allocation quality (i.e. more students have highly preferred projects). That's basically what I've currently got. Simple and it works. Now I'm working on this algorithm that tries to minimise the allocation weight locally (this pseudocode is a bit messy, sorry). The only reason this will probably work is because my "search space" as it is, isn't particularly large (just a very general, anecdotal observation, mind you). Since the project is only specific to my Department, we have their own limits imposed. So the number of students can't exceed 100 and the number of preferences won't exceed 10. for student in a dictionary/list/whatever of students: where i = 0 take the (i)st student, (i+1)nd student for their ranks: allocate the projects and set local_weighting to be sum(student_i.alloc_proj_rank, student_i+1.alloc_proj_rank) these are the cases: if local_weighting is 2 (i.e. both ranks are 1): then i += 1 and and continue above if local weighting is = N>2 (i.e. one or more ranks are greater than 1): let temp_local_weighting be N: pick student with lowest rank and then move him to his next rank and pick the other student and reallocate his project after this if temp_local_weighting is < N: then allocate those projects to the students move student with lowest rank to the next rank and reallocate other if temp_local_weighting < previous_temp_allocation: let these be the new allocated projects try moving for the lowest rank and reallocate other else: if this weighting => previous_weighting let these be the allocated projects i += 1 and move on for the rest of the students So, questions: This is sort of a modification of simulated annealing, but any sort of comments on this would be appreciated. How would I keep track of which student is (i) and which student is (i+1) If my overall list of students is 100, then the thing would mess up on (i+1) = 101 since there is none. How can I circumvent that? Any immediate flaws that can be spotted? Extra info: My students dictionary is designed as such: students[student_id] = Student(student_id, student_name, alloc_proj, alloc_proj_rank, preferences) where preferences is in the form of a dictionary such that preferences[rank] = {project_id}

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• A format for storing personal contacts in a database

  - by Gart

  I'm thinking of the best way to store personal contacts in a database for a business application. The traditional and straightforward approach would be to create a table with columns for each element, i.e. Name, Telephone Number, Job title, Address, etc... However, there are known industry standards for this kind of data, like for example vCard, or hCard, or vCard-RDF/XML or even Windows Contacts XML Schema. Utilizing an standard format would offer some benefits, like inter-operablilty with other systems. But how can I decide which method to use? The requirements are mainly to store the data. Search and ordering queries are highly unlikely but possible. The volume of the data is 100,000 records at maximum. My database engine supports native XML columns. I have been thinking to use some XML-based format to store the personal contacts. Then it will be possible to utilize XML indexes on this data, if searching and ordering is needed. Is this a good approach? Which contacts format and schema would you recommend for this? Edited after first answers Here is why I think the straightforward approach is bad. This is due to the nature of this kind of data - it is not that simple. The personal contacts it is not well-structured data, it may be called semi-structured. Each contact may have different data fields, maybe even such fields which I cannot anticipate. In my opinion, each piece of this data should be treated as important information, i.e. no piece of data could be discarded just because there was no relevant column in the database. If we took it further, assuming that no data may be lost, then we could create a big text column named Comment or Description or Other and put there everything which cannot be fitted well into table columns. But then again - the data would lose structure - this might be bad. If we wanted structured data then - according to the database design principles - the data should be decomposed into entities, and relations should be established between the entities. But this adds complexity - there are just too many entities, and lots of design desicions should be made, like "How do we store Address? Personal Name? Phone number? How do we encode home phone numbers and mobile phone numbers? How about other contact info?.." The relations between entities are complex and multiple, and each relation is a table in the database. Each relation needs to be documented in the design papers. That is a lot of work to do. But it is possible to avoid the complexity entirely - just document that the data is stored according to such and such standard schema, period. Then anybody who would be reading that document should easily understand what it was all about. Finally, this is all about using an industry standard. The standard is, hopefully, designed by some clever people who anticipated and described the structure of personal contacts information much better than I ever could. Why should we all reinvent the wheel?? It's much easier to use a standard schema. The problem is, there are just too many standards - it's not easy to decide which one to use!

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• handling long running large transactions with perl dbi

  - by 1stdayonthejob

  I've got a large transaction comprising of getting lots of data from database A, do some manipulations with this data, then inserting the manipulated data into database B. I've only got permissions to select in database A but I can create tables and insert/update etc in database B. The manipulation and insertion part is written in perl and already in use for loading data into database B from other data sources, so all that's required is to get the necessary data from database A and using it to initialize the perl classes. How can I go about doing this so I can easily track back and pick up from where the error happened if any error occurs during the manipulation or insertion procedures (database disconnection, problems with class initialization because of invalid values, hard disk failure etc...)? Doing the transaction in one go doesn't seem like a good option because the amount data from database A means it would take at least a day or 2 for data manipulation and insertion into database B. The data from database A can be grouped into around 1000 groups using unique keys, with each key containing 1000s of rows each. One way I thought I could do is to write a script that does commits per group, meaning I've got to track which group has already been inserted into database B. The only way I can think of to track the progress of which groups have been processed or not is either in a log file or in a table in database B. A second way I thought could work is to dump all the necessary fields needed for loading the classes for manipulation and insertion into a flatfile, read the file to initialize the classes and insert into database B. This also means that I got to do some logging, but should narrow it down to the exact row in the flatfile if any error occurs. The script will look something like this: use strict; use warnings; use DBI; #connect to database A my $dbh = DBI->connect('dbi:oracle:my_db', $user, $password, { RaiseError => 1, AutoCommit => 0 }); #statement to get data based on group unique key my $sth = $dbh->prepare($my_sql); my @groups; #I have a list of this already open my $fh, '>>', 'my_logfile' or die "can't open logfile $!"; eval { foreach my $g (@groups){ #subroutine to check if group has already been processed, either from log file or from database table next if is_processed($g); $sth->execute($g); my $data = $sth->fetchall_arrayref; #manipulate $data, then use it to load perl classes for insertion into database B #. #. #. } print $fh "$g\n"; }; if ($@){ $dbh->rollback; die "something wrong...rollback"; } So if any errors do occur, I can just run this script again and it should skip the groups or rows that have been processed and continue. Both these methods is just variations on the same theme, and both require going back to where I've been tracking my progress (in table or file), skip the ones that've been commited to database B and process the remaining data. I'm sure there's a better way of doing this but am struggling to think of other solutions. Is there another way of handling large transactions between databases that require data manipulation between getting data out from one and inserting into another? The process doesn't need to be all in Perl, as long as I can reuse the perl classes for manipulating and inserting the data into the database.

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• Persistence classes in Qt

  - by zarzych

  Hi, I'm porting a medium-sized CRUD application from .Net to Qt and I'm looking for a pattern for creating persistence classes. In .Net I usually created abstract persistence class with basic methods (insert, update, delete, select) for example: public class DAOBase<T> { public T GetByPrimaryKey(object primaryKey) {...} public void DeleteByPrimaryKey(object primaryKey) {...} public List<T> GetByField(string fieldName, object value) {...} public void Insert(T dto) {...} public void Update(T dto) {...} } Then, I subclassed it for specific tables/DTOs and added attributes for DB table layout: [DBTable("note", "note_id", NpgsqlTypes.NpgsqlDbType.Integer)] [DbField("note_id", NpgsqlTypes.NpgsqlDbType.Integer, "NoteId")] [DbField("client_id", NpgsqlTypes.NpgsqlDbType.Integer, "ClientId")] [DbField("title", NpgsqlTypes.NpgsqlDbType.Text, "Title", "")] [DbField("body", NpgsqlTypes.NpgsqlDbType.Text, "Body", "")] [DbField("date_added", NpgsqlTypes.NpgsqlDbType.Date, "DateAdded")] class NoteDAO : DAOBase<NoteDTO> { } Thanks to .Net reflection system I was able to achieve heavy code reuse and easy creation of new ORMs. The simplest way to do this kind of stuff in Qt seems to be using model classes from QtSql module. Unfortunately, in my case they provide too abstract an interface. I need at least transactions support and control over individual commits which QSqlTableModel doesn't provide. Could you give me some hints about solving this problem using Qt or point me to some reference materials? Update: Based on Harald's clues I've implemented a solution that is quite similar to the .Net classes above. Now I have two classes. UniversalDAO that inherits QObject and deals with QObject DTOs using metatype system: class UniversalDAO : public QObject { Q_OBJECT public: UniversalDAO(QSqlDatabase dataBase, QObject *parent = 0); virtual ~UniversalDAO(); void insert(const QObject &dto); void update(const QObject &dto); void remove(const QObject &dto); void getByPrimaryKey(QObject &dto, const QVariant &key); }; And a generic SpecializedDAO that casts data obtained from UniversalDAO to appropriate type: template<class DTO> class SpecializedDAO { public: SpecializedDAO(UniversalDAO *universalDao) virtual ~SpecializedDAO() {} DTO defaultDto() const { return DTO; } void insert(DTO dto) { dao->insert(dto); } void update(DTO dto) { dao->update(dto); } void remove(DTO dto) { dao->remove(dto); } DTO getByPrimaryKey(const QVariant &key); }; Using the above, I declare the concrete DAO class as following: class ClientDAO : public QObject, public SpecializedDAO<ClientDTO> { Q_OBJECT public: ClientDAO(UniversalDAO *dao, QObject *parent = 0) : QObject(parent), SpecializedDAO<ClientDTO>(dao) {} }; From within ClientDAO I have to set some database information for UniversalDAO. That's where my implementation gets ugly because I do it like this: QMap<QString, QString> fieldMapper; fieldMapper["client_id"] = "clientId"; fieldMapper["name"] = "firstName"; /* ...all column <-> field pairs in here... */ dao->setFieldMapper(fieldMapper); dao->setTable("client"); dao->setPrimaryKey("client_id"); I do it in constructor so it's not visible at a first glance for someone browsing through the header. In .Net version it was easy to spot and understand. Do you have some ideas how I could make it better?

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• Optimal storage of data structure for fast lookup and persistence

  - by Mikael Svenson

  Scenario I have the following methods: public void AddItemSecurity(int itemId, int[] userIds) public int[] GetValidItemIds(int userId) Initially I'm thinking storage on the form: itemId -> userId, userId, userId and userId -> itemId, itemId, itemId AddItemSecurity is based on how I get data from a third party API, GetValidItemIds is how I want to use it at runtime. There are potentially 2000 users and 10 million items. Item id's are on the form: 2007123456, 2010001234 (10 digits where first four represent the year). AddItemSecurity does not have to perform super fast, but GetValidIds needs to be subsecond. Also, if there is an update on an existing itemId I need to remove that itemId for users no longer in the list. I'm trying to think about how I should store this in an optimal fashion. Preferably on disk (with caching), but I want the code maintainable and clean. If the item id's had started at 0, I thought about creating a byte array the length of MaxItemId / 8 for each user, and set a true/false bit if the item was present or not. That would limit the array length to little over 1mb per user and give fast lookups as well as an easy way to update the list per user. By persisting this as Memory Mapped Files with the .Net 4 framework I think I would get decent caching as well (if the machine has enough RAM) without implementing caching logic myself. Parsing the id, stripping out the year, and store an array per year could be a solution. The ItemId - UserId[] list can be serialized directly to disk and read/write with a normal FileStream in order to persist the list and diff it when there are changes. Each time a new user is added all the lists have to updated as well, but this can be done nightly. Question Should I continue to try out this approach, or are there other paths which should be explored as well? I'm thinking SQL server will not perform fast enough, and it would give an overhead (at least if it's hosted on a different server), but my assumptions might be wrong. Any thought or insights on the matter is appreciated. And I want to try to solve it without adding too much hardware :) [Update 2010-03-31] I have now tested with SQL server 2008 under the following conditions. Table with two columns (userid,itemid) both are Int Clustered index on the two columns Added ~800.000 items for 180 users - Total of 144 million rows Allocated 4gb ram for SQL server Dual Core 2.66ghz laptop SSD disk Use a SqlDataReader to read all itemid's into a List Loop over all users If I run one thread it averages on 0.2 seconds. When I add a second thread it goes up to 0.4 seconds, which is still ok. From there on the results are decreasing. Adding a third thread brings alot of the queries up to 2 seonds. A forth thread, up to 4 seconds, a fifth spikes some of the queries up to 50 seconds. The CPU is roofing while this is going on, even on one thread. My test app takes some due to the speedy loop, and sql the rest. Which leads me to the conclusion that it won't scale very well. At least not on my tested hardware. Are there ways to optimize the database, say storing an array of int's per user instead of one record per item. But this makes it harder to remove items.

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• The best cross platform (portable) arbitrary precision math library

  - by Siu Ching Pong - Asuka Kenji

  Dear ninjas / hackers / wizards, I'm looking for a good arbitrary precision math library in C or C++. Could you please give me some advices / suggestions? The primary requirements: It MUST handle arbitrarily big integers (my primary interest is on integers). In case that you don't know what the word arbitrarily big means, imagine something like 100000! (the factorial of 100000). The precision MUST NOT NEED to be specified during library initialization / object creation. The precision should ONLY be constrained by the available resources of the system. It SHOULD utilize the full power of the platform, and should handle "small" numbers natively. That means on a 64-bit platform, calculating 2^33 + 2^32 should use the available 64-bit CPU instructions. The library SHOULD NOT calculate this in the same way as it does with 2^66 + 2^65 on the same platform. It MUST handle addition (+), subtraction (-), multiplication (*), integer division (/), remainder (%), power (**), increment (++), decrement (--), gcd(), factorial(), and other common integer arithmetic calculations efficiently. Ability to handle functions like sqrt() (square root), log() (logarithm) that do not produce integer results is a plus. Ability to handle symbolic computations is even better. Here are what I found so far: Java's BigInteger and BigDecimal class: I have been using these so far. I have read the source code, but I don't understand the math underneath. It may be based on theories / algorithms that I have never learnt. The built-in integer type or in core libraries of bc / Python / Ruby / Haskell / Lisp / Erlang / OCaml / PHP / some other languages: I have ever used some of these, but I have no idea on which library they are using, or which kind of implementation they are using. What I have already known: Using a char as a decimal digit, and a char* as a decimal string and do calculations on the digits using a for-loop. Using an int (or a long int, or a long long) as a basic "unit" and an array of it as an arbitrary long integer, and do calculations on the elements using a for-loop. Booth's multiplication algorithm What I don't know: Printing the binary array mentioned above in decimal without using naive methods. Example of a naive method: (1) add the bits from the lowest to the highest: 1, 2, 4, 8, 16, 32, ... (2) use a char* string mentioned above to store the intermediate decimal results). What I appreciate: Good comparisons on GMP, MPFR, decNumber (or other libraries that are good in your opinion). Good suggestions on books / articles that I should read. For example, an illustration with figures on how a un-naive arbitrarily long binary to decimal conversion algorithm works is good. Any help. Please DO NOT answer this question if: you think using a double (or a long double, or a long long double) can solve this problem easily. If you do think so, it means that you don't understand the issue under discussion. you have no experience on arbitrary precision mathematics. Thank you in advance! Asuka Kenji

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• LinkButtons Created Dynamically in a Repeater Don't Fire ItemCommand Event

  - by 5arx

  Hi. I've got a repeater that's used to display the output of a dynamic report that takes criteria from webcontrols on the page. Within the repeater's ItemDataBound method I'm adding controls (Linkbuttons for sorting by column values) dynamically to the header of the repeater based on values selected in a checkbox list and at this point setting the CommandArgument and CommandName properties of the linkbuttons. The issue is that when the linkbuttons are clicked they don't fire the ItemCommand event although they are clearly being correctly created and added to the header (there is some additional code to set the cssClass, text etc. and this works as expected.) The first column header in the repeater is set in the markup and the itemcommand event fires correctly on this one only. When the other column headers are clicked the repeater rebinds as programmed, but the columns are not dynamically re-generated. I would really appreciate somebody explaining what I'm doing wrong - afaik I'm following the approved way of doing this :-( Simplified code follows: Nightmare.ascx <asp:repeater runat="server" id="rptReport" OnItemDataBound="rptResults_ItemDataBound" OnItemCommand="rptResults_ItemCommand" EnableViewState="true"> <headertemplate> <table> <tr runat="Server" id="TRDynamicHeader"> <th> <!-- This one works --> <asp:Linkbutton runat="server" CommandName="sort" commandArgument='<%# Eval("Name")%?' /> </th> <!-- additional header cells get added dynamically here --> </tr> </headertemplate> <itemTemplate> <td><%# Eval("Name")</td> ... </itemTemplate> </asp:repeater> Nightmare.ascx.cs protected void PageLoad(object sender, eventArgs e){ if (! isPostback){ setupGui();//just binds dropdowns etc. to datasources } } protected void btnRunReport_Click(...){ List<ReportLines> lstRep = GetReportLines(); rptReport.DataSource = lstRep; repReport.DataBind(); } protected void rptReport_ItemDataBound (...){ if (e.Item.ItemType == ListItemType.Header) { foreach (ListItem li in chbxListBusFuncs.Items) { if (li.Selected) { th = new HtmlTableCell(); lb = new LinkButton(); lb.CssClass = "SortColHeader"; lb.CommandArgument = li.Text.Replace(" ", ""); lb.CommandName = "sort"; lb.Text = li.Text; th.Controls.Add(lb); ((HtmlTableRow)e.Item.FindControl("TRDynamicHeader")).Cells.Add(th); } } } if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem) { //Row level customisations, totals calculations etc. } } <!-- this only gets called when the 'hardcoded' linkbutton in the markup is clicked. protected void rptReport_ItemCommand(object sender, Eventargs e){ lblDebug.Text = string.Format("Well? What's Happening? -> {0}:{1}", e.CommandName, e.CommandArgument.ToString()); } (The only thing that can call the runreport routine is a single button on the page, not shown in the code snippet above.)

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• OSGI Declarative Services (DS): What is a good way of using service component instances

  - by Christoph

  I am just getting started with OSGI and Declarative Services (DS) using Equinox and Eclipse PDE. I have 2 Bundles, A and B. Bundle A exposes a component which is consumed by Bundle B. Both bundles also expose this service to the OSGI Service registry again. Everything works fine so far and Equinox is wireing the components together, which means the Bundle A and Bundle B are instanciated by Equinox (by calling the default constructor) and then the wireing happens using the bind / unbind methods. Now, as Equinox is creating the instances of those components / services I would like to know what is the best way of getting this instance? So assume there is third class class which is NOT instantiated by OSGI: Class WantsToUseComponentB{ public void doSomethingWithComponentB(){ // how do I get componentB??? Something like this maybe? ComponentB component = (ComponentB)someComponentRegistry.getComponent(ComponentB.class.getName()); } I see the following options right now: 1. Use a ServiceTracker in the Activator to get the Service of ComponentBundleA.class.getName() (I have tried that already and it works, but it seems to much overhead to me) and make it available via a static factory methods public class Activator{ private static ServiceTracker componentBServiceTracker; public void start(BundleContext context){ componentBServiceTracker = new ServiceTracker(context, ComponentB.class.getName(),null); } public static ComponentB getComponentB(){ return (ComponentB)componentBServiceTracker.getService(); }; } 2. Create some kind of Registry where each component registers as soon as the activate() method is called. public ComponentB{ public void bind(ComponentA componentA){ someRegistry.registerComponent(this); } or public ComponentB{ public void activate(ComponentContext context){ someRegistry.registerComponent(this); } } } 3. Use an existing registry inside osgi / equinox which has those instances? I mean OSGI is already creating instances and wires them together, so it has the objects already somewhere. But where? How can I get them? Conclusion Where does the class WantsToUseComponentB (which is NOT a Component and NOT instantiated by OSGI) get an instance of ComponentB from? Are there any patterns or best practises? As I said I managed to use a ServiceTracker in the Activator, but I thought that would be possible without it. What I am looking for is actually something like the BeanContainer of Springframework, where I can just say something like Container.getBean(ComponentA.BEAN_NAME). But I don't want to use Spring DS. I hope that was clear enough. Otherwise I can also post some source code to explain in more detail. Thanks Christoph UPDATED: Answer to Neil's comment: Thanks for clarifying this question against the original version, but I think you still need to state why the third class cannot be created via something like DS. Hmm don't know. Maybe there is a way but I would need to refactor my whole framework to be based on DS, so that there are no "new MyThirdClass(arg1, arg2)" statements anymore. Don't really know how to do that, but I read something about ComponentFactories in DS. So instead of doing a MyThirdClass object = new MyThirdClass(arg1, arg2); I might do a ComponentFactory myThirdClassFactory = myThirdClassServiceTracker.getService(); // returns a if (myThirdClassFactory != null){ MyThirdClass object = objectFactory.newInstance(); object.setArg1("arg1"); object.setArg2("arg2"); } else{ // here I can assume that some service of ComponentA or B went away so MyThirdClass Componenent cannot be created as there are missing dependencies? } At the time of writing I don't know exactly how to use the ComponentFactories but this is supposed to be some kind of pseudo code :) Thanks Christoph

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• Chaining CSS classes in IE6 - Trying to find a jQuery solution?

  - by Mike Baxter

  Right, perhaps I ask the impossible? I consider myself fairly new to Javscript and jQuery, but that being said, I have written some fairly complex code recently so I am definitely getting there... however I am now possed with a rather interesting issue at my current freelance contract. The previous web coder has taken a Grid-960 approach to the HTML and as a result has used chained classes to style many of the elements. The example below is typical of what can be found in the code: <div class='blocks four-col-1 orange highlight'>Some content</div> And in the css there will be different declarations for: (not actual css... but close enough) .blocks {margin-right:10px;} .orange {background-image:url(someimage.jpg);} .highlight {font-weight:bold;} .four-col-1 {width:300px;} and to make matters worse... this is in the CSS: .blocks.orange.highlight {background-colour:#dd00ff;} Anyone not familiar with this particular bug can read more on it here: http://www.ryanbrill.com/archives/multiple-classes-in-ie/ it is very real and very annoying. Without wanting to go into the merrits of not chaining classes (I told them this, but it is no longer feasible to change their approach... 100 hand coded pages into a 150 page website, no CMS... sigh) and without the luxury of being able to change the way these blocks are styled... can anyone advise me on the complexity and benefits between any of my below proposed approaches or possible other options that would adequately solve this problem. Potential Solution 1 Using conditional comments I am considering loading a jquery script only for IE6 that: Reads the class of all divs in a certain section of the page and pushes to an array creates empty boxes off screen with only one of the classes applied at a time Reads the applied CSS values for each box Re-applies these styles to the individual box, somehow bearing in mind the order in which they are called and overwriting conflicting instructions as required Potential Solution 2 read the class of all divs in a certain section of the page and push to an array Scan the document for links to style sheets Ajax grab the stylesheets and traverse looking for matching names to those in class array Apply styles as needed Potential Solution 3 Create an IE6 only stylesheet containing the exact style to be applied as a unique name (ie: class='blocks orange highlight' becomes class='blocks-orange-highlight') Traverse the document in IE6 and convert all spaces in class declarations to hyphens and reapply classes based on new style name Summary: Solution 1 allows the people at this company to apply any styles in the future and the script will adjust as needed. However it does not allow for the chained style to be added, only the individual style... it is also processor intensive and time consuming, but also the most likely to be converted into a plugin that could be used the world over Solution 2 is a potential nightmare to code. But again will allow for an endless number of updates without breaking Solution 3 will require someone at the companty to hardcode the new styles every time they make a change, and if they don't, IE6 will break. Ironically the site, whilst needing to conform to IE6 in a limited manner, does not need to run wihtout javascript (they've made the call... have JS or go away), so consider all jQuery and JS solutions to be 'game on'. Did I mention how much i hate IE6? Anyway... any thoughts or comments would be appreciated. I will continue to develop my own solution and if I discover one that can be turned into a jQuery plugin I will post it here in the comments. Regards, Mike.

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• How can I get Firefox to update background-color on a:hover *before* a javascript routine is run?

  - by Rob

  I'm having a Firefox-specific issue with a script I wrote to create 3d layouts. The correct behavior is that the script pulls the background-color from an element and then uses that color to draw on the canvas. When a user mouses over a link and the background-color changes to the :hover rule, the color being drawn changes on the canvas changes as well. When the user mouses out, the color should revert back to non-hover color. This works as expected in Webkit browsers and Opera, but it seems like Firefox doesn't update the background-color in CSS immediately after a mouseout event occurs, so the current background-color doesn't get drawn if a mouseout occurs and it isn't followed up by another event that calls the draw() routine. It works just fine in Opera, Chrome, and Safari. How can I get Firefox to cooperate? I'm including the code that I believe is most relevant to my problem. Any advice on how I fix this problem and get a consistent effect would be very helpful. function drawFace(coord, mid, popColor,gs,x1,x2,side) { /*Gradients in our case run either up/down or left right. We have two algorithms depending on whether or not it's a sideways facing piece. Rather than parse the "rgb(r,g,b)" string(popColor) retrieved from elsewhere, it is simply offset with the gs variable to give the illusion that it starts at a darker color.*/ var canvas = document.getElementById('depth'); //This is for excanvas.js var G_vmlCanvasManager; if (G_vmlCanvasManager != undefined) { // ie IE G_vmlCanvasManager.initElement(canvas); } //Init canvas if (canvas.getContext) { var ctx = canvas.getContext('2d'); if (side) var lineargradient=ctx.createLinearGradient(coord[x1][0]+gs,mid[1],mid[0],mid[1]); else var lineargradient=ctx.createLinearGradient(coord[0][0],coord[2][1]+gs,coord[0][0],mid[1]); lineargradient.addColorStop(0,popColor); lineargradient.addColorStop(1,'black'); ctx.fillStyle=lineargradient; ctx.beginPath(); //Draw from one corner to the midpoint, then to the other corner, //and apply a stroke and a fill. ctx.moveTo(coord[x1][0],coord[x1][1]); ctx.lineTo(mid[0],mid[1]); ctx.lineTo(coord[x2][0],coord[x2][1]); ctx.stroke(); ctx.fill(); } } function draw(e) { var arr = new Array() var i = 0; var mid = new Array(2); $(".pop").each(function() { mid[0]=Math.round($(document).width()/2); mid[1]=Math.round($(document).height()/2); arr[arr.length++]=new getElemProperties(this,mid); i++; }); arr.sort(sortByDistance); clearCanvas(); for (a=0;a<i;a++) { /*In the following conditional statements, we're testing to see which direction faces should be drawn, based on a 1-point perspective drawn from the midpoint. In the first statement, we're testing to see if the lower-left hand corner coord[3] is higher on the screen than the midpoint. If so, we set it's gradient starting position to start at a point in space 60pixels higher(-60) than the actual side, and we also declare which corners make up our face, in this case the lower two corners, coord[3], and coord[2].*/ if (arr[a].bottomFace) drawFace(arr[a].coord,mid,arr[a].popColor,-60,3,2); if (arr[a].topFace) drawFace(arr[a].coord,mid,arr[a].popColor,60,0,1); if (arr[a].leftFace) drawFace(arr[a].coord,mid,arr[a].popColor,60,0,3,true); if (arr[a].rightFace) drawFace(arr[a].coord,mid,arr[a].popColor,-60,1,2,true); } } $("a.pop").bind("mouseenter mouseleave focusin focusout",draw); If you need to see the effect in action, or if you want the full javascript code, you can check it out here: http://www.robnixondesigns.com/strangematter/

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• How to manage a MotionEvent going from one View to another?

  - by Darren

  I have a SurfaceView that takes up part of the screen, and some buttons along the bottom. When a button is pressed and the user drags, I want to be able to drag a picture (based on the button) onto the SurfaceView and have it drawn there. I want to be able to use clickListeners and the like, and not just have a giant SurfaceView with me writing code to detect where the user pressed and if it's a button, etc. I have somewhat of a solution, but it seems a bit of a hack to me. What is the best way to accomplish this using the framework intelligently? Part of my XML: <RelativeLayout android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="@drawable/background"> <!-- Place buttons along the bottom --> <RelativeLayout android:id="@+id/bottom_bar" android:orientation="horizontal" android:layout_width="fill_parent" android:layout_height="40dip" android:layout_alignParentBottom="true" android:background="@null"> <ImageButton android:id="@+id/btn_1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerVertical="true" android:background="@null" android:src="@drawable/btn_1"> </ImageButton> <!-- More buttons here... --> </RelativeLayout> <!-- Place the SurfaceView in a frame so we can stack on top of it --> <FrameLayout android:layout_width="fill_parent" android:layout_height="0px" android:layout_weight="1" android:layout_above="@id/bottom_bar"> <com.project.question.MySurfaceView android:id="@+id/my_view" android:layout_width="fill_parent" android:layout_height="fill_parent" /> </FrameLayout> And the relevant Java code in MySurfaceView, which extends SurfaceView. mTouchX and Y are used in the onDraw method to draw the image: @Override public boolean onTouchEvent(MotionEvent event){ mTouchX = (int) event.getX(); mTouchY = (int) event.getY(); return true; } public void onButtonTouchEvent(MotionEvent event){ event.setLocation(event.getX(), event.getY() + mScreenHeight); onTouchEvent(event); } Finally, the activity: @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); setContentView(R.layout.my_surface); mView = (MySurfaceView) findViewById(R.id.my_view); mSurfaceHeight = mView.getHeight(); mBtn = (ImageButton) findViewById(R.id.btn_1); mBtn.setOnTouchListener(mTouchListener); } OnTouchListener mTouchListener = new OnTouchListener() { public boolean onTouch(View v, MotionEvent event) { int [] location = new int[2]; v.getLocationOnScreen(location); event.setLocation(event.getX() + location[0], event.getY()); mView.onButtonTouchEvent(event); return true; } }; Strangely, one has to add to the x-coordinate in the activity, then add to the y coordinate in the View. Otherwise, it doesn't show up in the correct position. If you add nothing, something drawn using mTouchX and mTouchY will show up in the upper left corner of the SurfaceView. Any direction would be greatly appreciated. If I'm going about this completely the wrong way, that would be good information too.

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• Should we develop a custom membership provider in this case?

  - by Allen

  I'll be adding a bounty to this, probably 200, more if you guys think its appropriate. I wont accept an answer until I can add a bounty so feel free to go ahead and answer now Summary Long story short, we've been tasked with gutting the authentication and authorization parts of a fairly old and bloated asp.net application that previously had all of these components written from scratch. Since our application isn't a typical one, and none of us have experience in asp.net's built in membership provider stuff, we're not sure if we should roll our own authentication and authorization again or if we should try to work within the asp.net membership provider mindset and develop our own membership provider. Our Application We have a fairly old asp.net application that gets installed at customer locations to service clients on a LAN. Admins create users (users do not sign up) and depending on the install, we may have the software integrated with LDAP. Currently, the LDAP integration bulk-imports the users to our database and when they login, it authenticates against LDAP so we dont have to manage their passwords. Nothing amazing there. Admins can assign users to 1 group and they can change the authorization of that group to manage access to various parts of the software. Groups are maintained by Admins (web based UI) and as said earlier, granted / denied permissions to certain functionality within the application. All this was completely written from the ground up without using any of the built in .net authorization or authentication. We literally have IsLoggedIn() methods that check for login and redirect to our login page if they aren't. Our Rewrite We've been tasked to integrate more tightly with LDAP, they want us to tie groups in our application to groups (or whatever types of containers that LDAP uses) in LDAP so that when a customer opt's to use our LDAP integration, they dont have to manage their users in LDAP AND in our application. The new way, they will simply create users in LDAP, add them to Groups in LDAP and our application will see that they belong to the appropriate LDAP group and authenticate and authorize them. In addition, we've been granted the go ahead to completely rip out the User authentication and authorization code and completely re-do it. Our Problem The problem is that none of us have any experience with asp.net membership provider functionality. The little bit of exposure I have to it makes me worry that it was not intended to be used for an application such as ours. Though, developing our own ASP.NET Membership Provider and Role Manager sounds like it would be a great experience and most likely the appropriate thing to do. Basically, I'm looking for advice, should we be using the ASP.NET Membership provider & Role Management API or should we continue to roll our own? I know this decision will be influenced by our requirements so I'm going over them below Our Requirements Just a quick n dirty list Maintain the ability to have a db of users and authenticate them and give admins (only, not users) the ability to CRUD users Allow the site to integrate with LDAP, when this is chosen, they don't want any users stored in the DB, only the relationship between Groups as they exist in our app / db and the Groups/Containers as they exist in LDAP. .net 3.5 is being used (mix of asp.net webforms and asp.net mvc) Has to work in ASP.NET and ASP.NET MVC (shouldn't be a problem I'm guessing) This can't be user centric, administrators need to be the only ones that CRUD (or import via ldap) users and groups We have to be able to Auth via LDAP when its configured to do so I always try to monitor my questions closely so feel free to ask for more info. Also, as a general summary of what I'm looking for in an answer is just. "You should/shouldn't use xyz, here's why". Links regarding asp.net membership provider and role management stuff are very welcome, most of the stuff I'm finding is 5+ years old. Edit: Added some stuff to "Our Rewrite"

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• Help me alter this query to get the desired results - New*

  - by sandeepan

  Please dump these data first CREATE TABLE IF NOT EXISTS `all_tag_relations` ( `id_tag_rel` int(10) NOT NULL AUTO_INCREMENT, `id_tag` int(10) unsigned NOT NULL DEFAULT '0', `id_tutor` int(10) DEFAULT NULL, `id_wc` int(10) unsigned DEFAULT NULL, PRIMARY KEY (`id_tag_rel`), KEY `All_Tag_Relations_FKIndex1` (`id_tag`), KEY `id_wc` (`id_wc`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=19 ; INSERT INTO `all_tag_relations` (`id_tag_rel`, `id_tag`, `id_tutor`, `id_wc`) VALUES (1, 1, 1, NULL), (2, 2, 1, NULL), (3, 6, 2, NULL), (4, 7, 2, NULL), (8, 3, 1, 1), (9, 4, 1, 1), (10, 5, 2, 2), (11, 4, 2, 2), (15, 8, 1, 3), (16, 9, 1, 3), (17, 10, 1, 4), (18, 4, 1, 4), (19, 1, 2, 5), (20, 4, 2, 5); CREATE TABLE IF NOT EXISTS `tags` ( `id_tag` int(10) unsigned NOT NULL AUTO_INCREMENT, `tag` varchar(255) DEFAULT NULL, PRIMARY KEY (`id_tag`), UNIQUE KEY `tag` (`tag`), KEY `id_tag` (`id_tag`), KEY `tag_2` (`tag`), KEY `tag_3` (`tag`), KEY `tag_4` (`tag`), FULLTEXT KEY `tag_5` (`tag`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=11 ; INSERT INTO `tags` (`id_tag`, `tag`) VALUES (1, 'Sandeepan'), (2, 'Nath'), (3, 'first'), (4, 'class'), (5, 'new'), (6, 'Bob'), (7, 'Cratchit'), (8, 'more'), (9, 'fresh'), (10, 'second'); CREATE TABLE IF NOT EXISTS `webclasses` ( `id_wc` int(10) NOT NULL AUTO_INCREMENT, `id_author` int(10) NOT NULL, `name` varchar(50) DEFAULT NULL, PRIMARY KEY (`id_wc`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=5 ; INSERT INTO `webclasses` (`id_wc`, `id_author`, `name`) VALUES (1, 1, 'first class'), (2, 2, 'new class'), (3, 1, 'more fresh'), (4, 1, 'second class'), (5, 2, 'sandeepan class'); About the system - The system consists of tutors and classes. - The data in the table All_Tag_Relations stores tag relations for each tutor registered and each class created by a tutor. The tag relations are used for searching classes. The current data dump corresponds to tutor "Sandeepan Nath" who has created classes named "first class", "more fresh", "second class" and tutor "Bob Cratchit" who has created classes "new class" and "Sandeepan class". I am trying for a search query performs AND logic on the search keywords and returns wvery such class for which the search terms are present in the class name or its tutor name To make it easy, following is the list of search terms and desired results:- Search term result classes (check the id_wc in the results) first class 1 Sandeepan Nath class 1 Sandeepan Nath 1,3 Bob Cratchit 2 Sandeepan Nath bob none Sandeepan Class 1,4,5 I have so far reached upto this query -- Two keywords search SET @tag1 = 4, @tag2 = 1; -- Setting some user variables to see where the ids go. SELECT wc.id_wc, sum( DISTINCT ( wtagrels.id_tag = @tag1 ) ) AS key_1_class_matches, sum( DISTINCT ( wtagrels.id_tag = @tag2 ) ) AS key_2_class_matches, sum( DISTINCT ( ttagrels.id_tag = @tag1 ) ) AS key_1_tutor_matches, sum( DISTINCT ( ttagrels.id_tag = @tag2 ) ) AS key_2_tutor_matches, sum( DISTINCT ( ttagrels.id_tag = wtagrels.id_tag ) ) AS key_class_tutor_matches FROM WebClasses as wc join all_tag_relations AS wtagrels on wc.id_wc = wtagrels.id_wc join all_tag_relations as ttagrels on (wc.id_author = ttagrels.id_tutor) WHERE ( wtagrels.id_tag = @tag1 OR wtagrels.id_tag = @tag2 OR ttagrels.id_tag = @tag1 OR ttagrels.id_tag = @tag2 ) GROUP BY wtagrels.id_wc LIMIT 0 , 20 For search with 1 or 3 terms, remove/add the variable part in this query. Tabulating my observation of the values of key_1_class_matches, key_2_class_matches,key_1_tutor_matches (say, class keys),key_2_tutor_matches for various cases (say, tutor keys). Search term expected result Observation first class 1 for class 1, all class keys+all tutor keys =1 Sandeepan Nath class 1 for class 1, one class key+ all tutor keys = 1 Sandeepan Nath 1,3 both tutor keys =1 for these classes Bob Cratchit 2 both tutor keys = 1 Sandeepan Nath bob none no complete tutor matches for any class I found a pattern that, for any case, the class(es) which should appear in the result have the highest number of matches (all class keys and tutor keys). E.g. searching "first class", only for class =1, total of key matches = 4(1+1+1+1) searching "Sandeepan Nath", for classes 1, 3,4(all classes by Sandeepan Nath) have all the tutor keys matching. But no pattern in the search for "Sandeepan Class" - classes 1,4,5 should match. Now, how do I put a condition into the query, based on that pattern so that only those classes are returned. Do I need to use full text search here because it gives a scoring/rank value indicating the strength of the match? Any sample query would help. Please note - I have already found solution for showing classes when any/all of the search terms match with the class name. http://stackoverflow.com/questions/3030022/mysql-help-me-alter-this-search-query-to-get-desired-results But if all the search terms are in tutor name, it does not work. So, I am modifying the query and experimenting.

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• Error Handling without Exceptions

  - by James

  While searching SO for approaches to error handling related to business rule validation , all I encounter are examples of structured exception handling. MSDN and many other reputable development resources are very clear that exceptions are not to be used to handle routine error cases. They are only to be used for exceptional circumstances and unexpected errors that may occur from improper use by the programmer (but not the user.) In many cases, user errors such as fields that are left blank are common, and things which our program should expect, and therefore are not exceptional and not candidates for use of exceptions. QUOTE: Remember that the use of the term exception in programming has to do with the thinking that an exception should represent an exceptional condition. Exceptional conditions, by their very nature, do not normally occur; so your code should not throw exceptions as part of its everyday operations. Do not throw exceptions to signal commonly occurring events. Consider using alternate methods to communicate to a caller the occurrence of those events and leave the exception throwing for when something truly out of the ordinary happens. For example, proper use: private void DoSomething(string requiredParameter) { if (requiredParameter == null) throw new ArgumentExpcetion("requiredParameter cannot be null"); // Remainder of method body... } Improper use: // Renames item to a name supplied by the user. Name must begin with an "F". public void RenameItem(string newName) { // Items must have names that begin with "F" if (!newName.StartsWith("F")) throw new RenameException("New name must begin with /"F/""); // Remainder of method body... } In the above case, according to best practices, it would have been better to pass the error up to the UI without involving/requiring .NET's exception handling mechanisms. Using the same example above, suppose one were to need to enforce a set of naming rules against items. What approach would be best? Having the method return a enumerated result? RenameResult.Success, RenameResult.TooShort, RenameResult.TooLong, RenameResult.InvalidCharacters, etc. Using an event in a controller class to report to the UI class? The UI calls the controller's RenameItem method, and then handles an AfterRename event that the controller raises and that has rename status as part of the event args? The controlling class directly references and calls a method from the UI class that handles the error, e.g. ReportError(string text). Something else... ? Essentially, I want to know how to perform complex validation in classes that may not be the Form class itself, and pass the errors back to the Form class for display -- but I do not want to involve exception handling where it should not be used (even though it seems much easier!) Based on responses to the question, I feel that I'll have to state the problem in terms that are more concrete: UI = User Interface, BLL = Business Logic Layer (in this case, just a different class) User enters value within UI. UI reports value to BLL. BLL performs routine validation of the value. BLL discovers rule violation. BLL returns rule violation to UI. UI recieves return from BLL and reports error to user. Since it is routine for a user to enter invalid values, exceptions should not be used. What is the right way to do this without exceptions?

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• Facebook - Publish Checkins using Graph API

  - by Zany

  I'm trying to publish Checkin using Facebook Graph API. I've gone through Facebook API documentation (checkins) and also have the publish_checkins permission. However, my checkin is not getting published. May I know is there anything wrong or am I missing anything else? Thank you for your time :) fbmain.php $user = $facebook->getUser(); $access_token = $facebook->getAccessToken(); // Session based API call if ($user) { try { $me = $facebook->api('/me'); if($me) { $_SESSION['fbID'] = $me['id']; $uid = $me['id']; } } catch (FacebookApiException $e) { error_log($e); } } else { echo "<script type='text/javascript'>top.location.href='$loginUrl';</script>"; exit; } $loginUrl = $facebook->getLoginUrl( array( 'redirect_uri' => $redirect_url, 'scope' => status_update, publish_stream, publish_checkins, user_checkins, user_location, user_status' ) ); main.php (Updated: 18/6/2012 11.12pm) <?php include_once "fbmain.php"; if (!isset($_POST['latitude']) && !isset($_POST['longitude'])) { ?> <html> <head> //ajax POST of latitude and longitude </head> <body> <script type="text/javascript"> window.fbAsyncInit = function() { FB.init({ appId: '<?php echo $facebook->getAppID() ?>', cookie: true, xfbml: true, oauth: true, frictionlessRequests: true }); FB.Canvas.setAutoGrow(); }; (function() { var e = document.createElement('script'); e.async = true; e.src = document.location.protocol + '//connect.facebook.net/en_US/all.js'; document.getElementById('fb-root').appendChild(e); }()); </script> ... <input type="button" value="Check In!" onclick="checkin(<?=$facebook?>);"/></span> </body> </html> <?php } else { print_r($_POST['latitude']); print_r($_POST['longitude']); ?> <script type="text/javascript"> // not using latitude and longitude to test function checkin($fb) { try { $tryCatch = $facebook->api('/'.$_SESSION['fbID'].'/checkins', 'POST', array( 'access_token' => $fb->getAccessToken(), //corrected 'place' => '165122993538708', 'message' =>'I went to placename today', 'coordinates' => json_encode(array( 'latitude' => '1.3019399200902', 'longitude' => '103.84067653695' )) )); } catch(FacebookApiException $e) { $tryCatch=$e->getMessage(); } return $tryCatch; } </script> <?php } ?>

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• Openlayers - LayerRedraw() / Feature rotation / Linestring coords

  - by Ozaki

  TLDR: I have an Openlayers map with a layer called 'track' I want to remove track and add track back in. Or figure out how to plot a triangle based off one set of coords & a heading(see below). I have an image 'imageFeature' on a layer that rotates on load to the direction being set. I want it to update this rotation that is set in 'styleMap' on a layer called 'tracking'. I set the var 'stylemap' to apply the external image & rotation. The 'imageFeature' is added to the layer at the coords specified. 'imageFeature' is removed. 'imageFeature' is added again in its new location. Rotation is not applied.. As the 'styleMap' applies to the layer I think that I have to remove the layer and add it again rather than just the 'imageFeature' Layer: var tracking = new OpenLayers.Layer.GML("Tracking", "coordinates.json", { format: OpenLayers.Format.GeoJSON, styleMap: styleMap }); styleMap: var styleMap = new OpenLayers.StyleMap({ fillOpacity: 1, pointRadius: 10, rotation: heading, }); Now wrapped in a timed function the imageFeature: map.layers[3].addFeatures(new OpenLayers.Feature.Vector( new OpenLayers.Geometry.Point(longitude, latitude), {rotation: heading, type: parseInt(Math.random() * 3)} )); Type refers to a lookup of 1 of 3 images.: styleMap.addUniqueValueRules("default", "type", lookup); var lookup = { 0: {externalGraphic: "Image1.png", rotation: heading}, 1: {externalGraphic: "Image2.png", rotation: heading}, 2: {externalGraphic: "Image3.png", rotation: heading} } I have tried the 'redraw()' function: but it returns "tracking is undefined" or "map.layers[2]" is undefined. tracking.redraw(true); map.layers[2].redraw(true); Heading is a variable: from a JSON feed. var heading = 13.542; But so far can't get anything to work it will only rotate the image onload. The image will move in coordinates as it should though. So what am I doing wrong with the redraw function or how can I get this image to rotate live? Thanks in advance -Ozaki Add: I managed to get map.layers[2].redraw(true); to sucessfully redraw layer 2. But it still does not update the rotation. I am thinking because the stylemap is updating. But it runs through the style map every n sec, but no updates to rotation and the variable for heading is updating correctly if i put a watch on it in firebug. If I were to draw a triangle with an array of points & linestring. How would I go about facing the triangle towards the heading. I have the Lon/lat of one point and the heading. var points = new Array( new OpenLayers.Geometry.Point(lon1, lat1), new OpenLayers.Geometry.Point(lon2, lat2), new OpenLayers.Geometry.Point(lon3, lat3) ); var line = new OpenLayers.Geometry.LineString(points); Looking for any way to solve this problem Image or Line anyone know how to do either added a 100rep bounty I am really stuck with this.

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• A methology that allows for a single Java code base covering many different versions?

  - by Thorbjørn Ravn Andersen

  I work in a small shop where we have a LOT of legacy Cobol code and where a methology has been adopted to allow us to minimize forking and branching as much as possible. For a given release we have three levels: CORE - bottom layer, this code is common to all releases GROUP - optional code common to several customers. CUSTOMER - optional code specific for a single customer. When a program is needed, it is first searched for in CUSTOMER, then in GROUP and finally in CORE. A given application for us invokes many programs which all are looked for in this sequence (think exe files and PATH under Windows). We also have Java programs interacting with this legacy code, and as the core-group-customer lookup mehchanism does not lend it self easily to Java it has tended to grow in a CVS branch for each customer, requiring much too much maintainance. The Java part and the backend part tend to be developed in parallel. I have been assigned to figure out a way to make the two worlds meet. Essentially we want a Java enviornment which allows us to have a single code base with sources for each release, where we easily can select a group and a customer and work with the application as it goes for that customer, and then easily switch to another codeset and THAT customer. I was thinking of perhaps a scenario with an Eclipse project for each core, customer, and group and then use Project Sets to select those we need for a given scenario. The problem I cannot get my head about, is how we would create robust code in the CORE projects which will work regardless of which group and customer is selected. A Factory class which knows which sub class of a passed Class object to invoke instead of each and every new? Others must have had similar code base management problems. Anybody with experiences to share? EDIT: The conclusion to this problem above has been that CVS needs to be replaced with a source code management system better suited for dealing with many branches concurrently and the migration of source from one component to the other while keeping history. Inspired by the recent migration by slf4j and logback we are currently looking at git as it handles branches very well. We've considered subversion and mercurial too but git appears to be better for single location, multibranched projects. I've asked about Perforce in another question, but my personal inclination is towards open source solutions for something as crucial as this. EDIT: After some more pondering, we've found that our actual pain point is that we use branches in CVS, and that branches in CVS are the easiest to work with if you branch ALL files! The revised conclusion is that we can do this with CVS alone, by switching to a forest of java projects, each corresponding to one of the levels above, and use the Eclipse build paths to tie them together so each CUSTOMER version pulls in the appropriate GROUP and CORE project. We still want to switch to a better versioning system but this is so important a decision so we want to delay it as much as possible. EDIT: I now have a proof-of-concept implementation of the CORE-GROUP-CUSTOMER concept using Google Guice 2.0 - the @ImplementedBy tag is just what we need. I wonder what everybody else does? Using if's all over the place? EDIT: Now I also need this functionality for web applications. Guice was until the JSR-330 is in place. Anybody with versioning experience? EDIT: JSR-330/299 is now in place with the JEE6 reference implementation Weld based on JBoss Seam and I have reimplemented the proof-of-concept with Weld and can see that if we use @Alternative along with ... in beans.xml we can get the behaviour we desire. I.e. provide a new implementation for a given functionality in CORE without changing a bit in the CORE jars. Initial reading up on the Servlet 3.0 specification indicates that it may support the same functionality for web application resources (not code). We will now do initial testing on the real application.

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• How to associate newly created SurfaceHolder to MediaPlayer

  - by fayerth

  In my code, I want to be able to temporarily hide (and subsequently show) a video. I am using a SurfaceView + MediaPlayer combination instead of the VideoView due to requirements. However, I am facing difficulties in getting video playback to occur as expected after I show the SurfaceView. My code excerpts includes the following: public void show() { if (mSurface != null) mSurface.setVisibility(View.VISIBLE); } public void hide() { if (mSurface != null) { if (isInPlaybackState()) pause(); mSurface.setVisibility(View.INVISIBLE); } } @Override public void surfaceCreated(final SurfaceHolder holder) { mHolder = holder; openVideo(); } @Override public void surfaceDestroyed(final SurfaceHolder holder) { // After this, the surface can't be used again mHolder = null; } private void openVideo() { if (mAssetPath == null || !mAssetPath.isEmpty() || mHolder == null) { // Not ready yet; try again later return; } // Pause music playback service Intent i = new Intent("com.android.music.musicservicecommand"); i.putExtra("command", "pause"); getActivity().sendBroadcast(i); if (mPlayer == null) { initializePlayer(); } else { mPlayer.setDisplay(mHolder); } } Based on the above, when I call hide(), surfaceDestroyed(SurfaceHolder) gets triggered. When I later call show(), surfaceCreated(SurfaceHolder) gets triggered, which will call openVideo() and associate the player with the newly provided SurfaceHolder. The above works as expected, and I believe this should be the correct process; however, when I call mPlayer.start(), I would hear the video's audio playing without any video and see the following error messages (which eventually causes the media playback to stop and complete, as noted by the disconnect logs): 10-23 11:29:42.775: E/MediaPlayer(4204): Error (1,-2147483648) 10-23 11:29:42.795: E/MediaPlayer(4204): Error (-38,0) 10-23 11:29:42.805: E/MediaPlayer(4204): Error (1,-2147483648) 10-23 11:29:42.810: V/MediaPlayer(4204): message received msg=100, ext1=1, ext2=-2147483648 10-23 11:29:42.810: E/MediaPlayer(4204): error (1, -2147483648) 10-23 11:29:42.810: V/MediaPlayer(4204): callback application 10-23 11:29:42.810: V/MediaPlayer(4204): back from callback 10-23 11:29:42.825: E/MediaPlayer(4204): Error (1,-2147483648) 10-23 11:29:42.850: V/MediaPlayer-JNI(4204): getCurrentPosition: 671668 (msec) 10-23 11:29:42.850: V/MediaPlayer-JNI(4204): getCurrentPosition: 671668 (msec) 10-23 11:29:42.850: V/MediaPlayer(4204): message received msg=100, ext1=1, ext2=-2147483648 10-23 11:29:42.850: E/MediaPlayer(4204): error (1, -2147483648) 10-23 11:29:42.850: V/MediaPlayer(4204): callback application 10-23 11:29:42.850: V/MediaPlayer(4204): back from callback 10-23 11:29:42.875: V/MediaPlayer-JNI(4204): stop 10-23 11:29:42.875: V/MediaPlayer(4204): stop 10-23 11:29:42.875: E/MediaPlayer(4204): stop called in state 0 10-23 11:29:42.875: V/MediaPlayer(4204): message received msg=100, ext1=-38, ext2=0 10-23 11:29:42.875: E/MediaPlayer(4204): error (-38, 0) 10-23 11:29:42.875: V/MediaPlayer(4204): callback application 10-23 11:29:42.875: V/MediaPlayer(4204): back from callback 10-23 11:29:42.875: V/MediaPlayer-JNI(4204): reset 10-23 11:29:42.875: V/MediaPlayer(4204): reset 10-23 11:29:42.900: V/MediaPlayer-JNI(4204): release 10-23 11:29:42.900: V/MediaPlayer(4204): setListener 10-23 11:29:42.900: V/MediaPlayer(4204): disconnect 10-23 11:29:42.910: V/MediaPlayer(4204): destructor 10-23 11:29:42.910: V/MediaPlayer(4204): disconnect Has anyone encountered this issue before and found a workaround? Or would the only option be to create a new MediaPlayer as well?

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• Help me alter this query to get the desired results

  - by sandeepan

  Please dump these data first CREATE TABLE IF NOT EXISTS `all_tag_relations` ( `id_tag_rel` int(10) NOT NULL AUTO_INCREMENT, `id_tag` int(10) unsigned NOT NULL DEFAULT '0', `id_tutor` int(10) DEFAULT NULL, `id_wc` int(10) unsigned DEFAULT NULL, PRIMARY KEY (`id_tag_rel`), KEY `All_Tag_Relations_FKIndex1` (`id_tag`), KEY `id_wc` (`id_wc`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=19 ; INSERT INTO `all_tag_relations` (`id_tag_rel`, `id_tag`, `id_tutor`, `id_wc`) VALUES (1, 1, 1, NULL), (2, 2, 1, NULL), (3, 6, 2, NULL), (4, 7, 2, NULL), (8, 3, 1, 1), (9, 4, 1, 1), (10, 5, 2, 2), (11, 4, 2, 2), (15, 8, 1, 3), (16, 9, 1, 3), (17, 10, 1, 4), (18, 4, 1, 4), (19, 1, 2, 5), (20, 4, 2, 5); CREATE TABLE IF NOT EXISTS `tags` ( `id_tag` int(10) unsigned NOT NULL AUTO_INCREMENT, `tag` varchar(255) DEFAULT NULL, PRIMARY KEY (`id_tag`), UNIQUE KEY `tag` (`tag`), KEY `id_tag` (`id_tag`), KEY `tag_2` (`tag`), KEY `tag_3` (`tag`), KEY `tag_4` (`tag`), FULLTEXT KEY `tag_5` (`tag`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=11 ; INSERT INTO `tags` (`id_tag`, `tag`) VALUES (1, 'Sandeepan'), (2, 'Nath'), (3, 'first'), (4, 'class'), (5, 'new'), (6, 'Bob'), (7, 'Cratchit'), (8, 'more'), (9, 'fresh'), (10, 'second'); CREATE TABLE IF NOT EXISTS `webclasses` ( `id_wc` int(10) NOT NULL AUTO_INCREMENT, `id_author` int(10) NOT NULL, `name` varchar(50) DEFAULT NULL, PRIMARY KEY (`id_wc`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=5 ; INSERT INTO `webclasses` (`id_wc`, `id_author`, `name`) VALUES (1, 1, 'first class'), (2, 2, 'new class'), (3, 1, 'more fresh'), (4, 1, 'second class'), (5, 2, 'sandeepan class'); About the system - The system consists of tutors and classes. - The data in the table All_Tag_Relations stores tag relations for each tutor registered and each class created by a tutor. The tag relations are used for searching classes. The current data dump corresponds to tutor "Sandeepan Nath" who has created classes named "first class", "more fresh", "second class" and tutor "Bob Cratchit" who has created classes "new class" and "Sandeepan class". I am trying for a search query performs AND logic on the search keywords and returns wvery such class for which the search terms are present in the class name or its tutor name To make it easy, following is the list of search terms and desired results:- Search term result classes (check the id_wc in the results) first class 1 Sandeepan Nath class 1 Sandeepan Nath 1,3 Bob Cratchit 2 Sandeepan Nath bob none Sandeepan Class 1,4,5 I have so far reached upto this query -- Two keywords search SET @tag1 = 4, @tag2 = 1; -- Setting some user variables to see where the ids go. SELECT wc.id_wc, sum( DISTINCT ( wtagrels.id_tag = @tag1 ) ) AS key_1_class_matches, sum( DISTINCT ( wtagrels.id_tag = @tag2 ) ) AS key_2_class_matches, sum( DISTINCT ( ttagrels.id_tag = @tag1 ) ) AS key_1_tutor_matches, sum( DISTINCT ( ttagrels.id_tag = @tag2 ) ) AS key_2_tutor_matches, sum( DISTINCT ( ttagrels.id_tag = wtagrels.id_tag ) ) AS key_class_tutor_matches FROM WebClasses as wc join all_tag_relations AS wtagrels on wc.id_wc = wtagrels.id_wc join all_tag_relations as ttagrels on (wc.id_author = ttagrels.id_tutor) WHERE ( wtagrels.id_tag = @tag1 OR wtagrels.id_tag = @tag2 OR ttagrels.id_tag = @tag1 OR ttagrels.id_tag = @tag2 ) GROUP BY wtagrels.id_wc LIMIT 0 , 20 For search with 1 or 3 terms, remove/add the variable part in this query. Tabulating my observation of the values of key_1_class_matches, key_2_class_matches,key_1_tutor_matches (say, class keys),key_2_tutor_matches for various cases (say, tutor keys). Search term expected result Observation first class 1 for class 1, all class keys+all tutor keys =1 Sandeepan Nath class 1 for class 1, one class key+ all tutor keys = 1 Sandeepan Nath 1,3 both tutor keys =1 for these classes Bob Cratchit 2 both tutor keys = 1 Sandeepan Nath bob none no complete tutor matches for any class I found a pattern that, for any case, the class(es) which should appear in the result have the highest number of matches (all class keys and tutor keys). E.g. searching "first class", only for class =1, total of key matches = 4(1+1+1+1) searching "Sandeepan Nath", for classes 1, 3,4(all classes by Sandeepan Nath) have all the tutor keys matching. But no pattern in the search for "Sandeepan Class" - classes 1,4,5 should match. Now, how do I put a condition into the query, based on that pattern so that only those classes are returned. Do I need to use full text search here because it gives a scoring/rank value indicating the strength of the match? Any sample query would help. Please note - I have already found solution for showing classes when any/all of the search terms match with the class name. http://stackoverflow.com/questions/3030022/mysql-help-me-alter-this-search-query-to-get-desired-results But if all the search terms are in tutor name, it does not work. So, I am modifying the query and experimenting.

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• Find optimal/good-enough strategy and AI for the game 'Proximity'?

  - by smci

  'Proximity' is a strategy game of territorial domination similar to Othello, Go and Risk. Two players, uses a 10x12 hex grid. Game invented by Brian Cable in 2007. Seems to be a worthy game for discussing a) optimal algorithm then b) how to build an AI. Strategies are going to be probabilistic or heuristic-based, due to the randomness factor, and the insane branching factor (20^120). So it will be kind of hard to compare objectively. A compute time limit of 5s per turn seems reasonable. Game: Flash version here and many copies elsewhere on the web Rules: here Object: to have control of the most armies after all tiles have been placed. Each turn you received a randomly numbered tile (value between 1 and 20 armies) to place on any vacant board space. If this tile is adjacent to any ally tiles, it will strengthen each tile's defenses +1 (up to a max value of 20). If it is adjacent to any enemy tiles, it will take control over them if its number is higher than the number on the enemy tile. Thoughts on strategy: Here are some initial thoughts; setting the computer AI to Expert will probably teach a lot: minimizing your perimeter seems to be a good strategy, to prevent flips and minimize worst-case damage like in Go, leaving holes inside your formation is lethal, only more so with the hex grid because you can lose armies on up to 6 squares in one move low-numbered tiles are a liability, so place them away from your main territory, near the board edges and scattered. You can also use low-numbered tiles to plug holes in your formation, or make small gains along the perimeter which the opponent will not tend to bother attacking. a triangle formation of three pieces is strong since they mutually reinforce, and also reduce the perimeter Each tile can be flipped at most 6 times, i.e. when its neighbor tiles are occupied. Control of a formation can flow back and forth. Sometimes you lose part of a formation and plug any holes to render that part of the board 'dead' and lock in your territory/ prevent further losses. Low-numbered tiles are obvious-but-low-valued liabilities, but high-numbered tiles can be bigger liabilities if they get flipped (which is harder). One lucky play with a 20-army tile can cause a swing of 200 (from +100 to -100 armies). So tile placement will have both offensive and defensive considerations. Comment 1,2,4 seem to resemble a minimax strategy where we minimize the maximum expected possible loss (modified by some probabilistic consideration of the value ß the opponent can get from 1..20 i.e. a structure which can only be flipped by a ß=20 tile is 'nearly impregnable'.) I'm not clear what the implications of comments 3,5,6 are for optimal strategy. Interested in comments from Go, Chess or Othello players. (The sequel ProximityHD for XBox Live, allows 4-player -cooperative or -competitive local multiplayer increases the branching factor since you now have 5 tiles in your hand at any given time, of which you can only play one. Reinforcement of ally tiles is increased to +2 per ally.)

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• WebSphere Application Server EJB Optimization

  - by Chris Aldrich

  We are working on developing a Java EE based application. Our application is Java 1.5 compatible and will be deployed to WAS ND 6.1.0.21 with EBJ 3.0 and Web Services feature packs. The configuration is currently one cell with two clusters. Each cluster will have two nodes. Our application, or our system, as I should rather say, comes in two or three parts. Part 1: An ear deployed to one cluster that contains 3rd party vendor code combined with customization code. Their code is EJB 2.0 compliant and has a lot of Remote Home interfaces. Part 2: An ear deployed to the same cluster as the first ear. This ear contains EBJ 3's that make calls into the EJB 2's supplied by the vendor and the custom code. These EJB 3's are used by the JSF UI also packaged with the EAR, and some of them are also exposed as web services (JAX-WS 2.0 with SOAP 1.2 compliance) for other clients. Part 3: There may be other services that do not depend on our vendor/custom code app. These services will be EJB 3.0's and web services that are deployed to the other cluster. Per a recommendation from some IBM staff on site here, communication between nodes in a cluster can be EJB RMI. But if we are going across clusters and/or other cells, then the communication should be web services. That said, some of us are wondering about performance and optimizing communication for speed of our applications that will use our web services and EJB's. Right now most EJB's are exposed as remote. (and our vendor set theirs up that way, rather than also exposing local home interfaces). We are wondering if WAS does any optimizations between apps in the same node/cluster node space. If two apps are installed in the same area and they call each other via remote home interface, is WAS smart enough to make it a local home interface call? Are their other optimization techniques? Should we consider them? Should we not? What are the costs/benefits? Here is the question from one of our team members as sent in their email: The question is: Supposing we develop our EJBs as remote EJBs, where our UI controller code is talking to our EXT java services via EJB3...what are our options for performance optimization when both the EJB server and client are running in the same container? As one point of reference, google has given me some oooooold websphere performance tuning documentation from 2000 that explains a tuning configuration you can set to enable Call By Reference for EJB communication when they're in the same application server JVM. It states the following: Because EJBs are inherently location independent, they use a remote programming model. Method parameters and return values are serialized over RMI-IIOP and returned by value. This is the intrinsic RMI "Call By Value" model. WebSphere provides the "No Local Copies" performance optimization for running EJBs and clients (typically servlets) in the same application server JVM. The "No Local Copies" option uses "Call By Reference" and does not create local proxies for called objects when both the client and the remote object are in the same process. Depending on your workload, this can result in a significant overhead savings. Configure "No Local Copies" by adding the following two command line parameters to the application server JVM: * -Djavax.rmi.CORBA.UtilClass=com.ibm.CORBA.iiop.Util * -Dcom.ibm.CORBA.iiop.noLocalCopies=true CAUTION: The "No Local Copies" configuration option improves performance by changing "Call By Value" to "Call By Reference" for clients and EJBs in the same JVM. One side effect of this is that the Java object derived (non-primitive) method parameters can actually be changed by the called enterprise bean. Consider Figure 16a: Also, we will also be using Process Server 6.2 and WESB 6.2 as well in the future. Any ideas? recommendations? Thanks

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