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• Daily, Weekly and Monthly Page View Counter

  - by Jens Fahnenbruck

  I'm building a website with user generated content. On the home page I want to show a list of all created items, and I want to be able to sort them by a view counter. That's sound easy, but I want multiple counters. I want to know which was the most visited item in the last day, last week or last months or overall. My first Idea was to create 4 counter columns in the item's DB-Table. One for each of daily, weekly, monthly and overall, and the create a cron job, that clears the daily counter every 24 hours, the weekly counter every 7 days and so on. But my problem with this is, what happens if I want to know which was the most viewed item of the week, just after the weekly counter got cleared? What I need is an efficient way to create a continous counter, which got reduced for every page view that is too old, and increased for every new page view. Right now I'm thinking of a solution with the redis server, but I have no solution yet. I'm just looking for a general idea here, but FYI I'm developing this application in Ruby on Rails.

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• Is it immoral to write crappy code even if readability and correctness is not a requirement?

  - by mafutrct

  There are cases when crappy (i.e. unreadable and buggy) code is not much of a problem. For instance, imagine you need to generate a big text file that mostly follows a simple pattern with a few very complex exceptions. What do you do? You quickly write a simple algorithm and insert the exceptional bits in the output manually to save 4 hours. The code is unreadable, and the output is flawed, but it's still the correct way since it is way faster. But let's get this straight: I hate bad code. I've had to read and work with code that caused my stomach to hurt. I care a lot about good code. And actually, I caught myself thinking that it is immoral to write bad code even though the dirty approach is sometimes superior. I was surprised by myself and found my idea to be very irrational. Did you ever experience this? Should I just get rid of this stupid idea and use the most efficient approach to coding?

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• mysql image disable print download

  - by Vish

  Hi, We use a Flex AIR client and a WAMP server. Tiff images are stored in MySQL. Currently, I can download the image from AIR client and it prompts for a download dialog. Things are fine till this point. We got a new requirement. Requirement is that only some users can print the image which gets downloaded. For other users, they should not be able to print the tiff image. Wondering how to accomplish this. One idea, not sure if its efficient, is to convert the image requested to pdf at the server side, disable print option there(hope there are API's available) and send back the pdf. Please let me know btter ideas. Also, is there a way to prevent file download dialog from popping up everytime the file is requested for download? Can we just get the file stream to the client and manipulate it to open with a particular viewer or write it to pdf... Please help.

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• Drawing to the canvas

  - by Mattl

  I'm writing an android application that draws directly to the canvas on the onDraw event of a View. I'm drawing something that involves drawing each pixel individually, for this I use something like: for (int x = 0; x < xMax; x++) { for (int y = 0; y < yMax; y++){ MyColour = CalculateMyPoint(x, y); canvas.drawPoint(x, y, MyColour); } } The problem here is that this takes a long time to paint as the CalculateMyPoint routine is quite an expensive method. Is there a more efficient way of painting to the canvas, for example should I draw to a bitmap and then paint the whole bitmap to the canvas on the onDraw event? Or maybe evaluate my colours and fill in an array that the onDraw method can use to paint the canvas? Users of my application will be able to change parameters that affect the drawing on the canvas. This is incredibly slow at the moment.

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• jQuery: Inserting li items one by one?

  - by Legend

  I wrote the following (part of a jQuery plugin) to insert a set of items from a JSON object into a <ul> element. ... query: function() { ... $.ajax({ url: fetchURL, type: 'GET', dataType: 'jsonp', timeout: 5000, error: function() { self.html("Network Error"); }, success: function(json) { //Process JSON $.each(json.results, function(i, item) { $("<li></li>") .html(mHTML) .attr('id', "div_li"+i) .attr('class', "divliclass") .prependTo("#" + "div_ul"); $(slotname + "div_li" + i).hide(); $(slotname + "div_li" + i).show("slow") } } }); } }); }, ... Doing this maybe adding the <li> items one by one theoretically but when I load the page, everything shows up instantaneously. Instead, is there an efficient way to make them appear one by one more slowly? I'll explain with a small example: If I have 3 items, this code is making all the 3 items appear instantaneously (at least to my eyes). I want something like 1 fades in, then 2 fades in, then 3 (something like a newsticker perhaps). Anyone has a suggestion?

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• Perform Grouping of Resultsets in Code, not on Database Level

  - by NinjaBomb

  Stackoverflowers, I have a resultset from a SQL query in the form of: Category Column2 Column3 A 2 3.50 A 3 2 B 3 2 B 1 5 ... I need to group the resultset based on the Category column and sum the values for Column2 and Column3. I have to do it in code because I cannot perform the grouping in the SQL query that gets the data due to the complexity of the query (long story). This grouped data will then be displayed in a table. I have it working for specific set of values in the Category column, but I would like a solution that would handle any possible values that appear in the Category column. I know there has to be a straightforward, efficient way to do it but I cannot wrap my head around it right now. How would you accomplish it? EDIT I have attempted to group the result in SQL using the exact same grouping query suggested by Thomas Levesque and both times our entire RDBMS crashed trying to process the query. I was under the impression that Linq was not available until .NET 3.5. This is a .NET 2.0 web application so I did not think it was an option. Am I wrong in thinking that? EDIT Starting a bounty because I believe this would be a good technique to have in the toolbox to use no matter where the different resultsets are coming from. I believe knowing the most concise way to group any 2 somewhat similar sets of data in code (without .NET LINQ) would be beneficial to more people than just me.

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• Polymorphic Numerics on .Net and In C#

  - by Bent Rasmussen

  It's a real shame that in .Net there is no polymorphism for numbers, i.e. no INumeric interface that unifies the different kinds of numerical types such as bool, byte, uint, int, etc. In the extreme one would like a complete package of abstract algebra types. Joe Duffy has an article about the issue: http://www.bluebytesoftware.com/blog/CommentView,guid,14b37ade-3110-4596-9d6e-bacdcd75baa8.aspx How would you express this in C#, in order to retrofit it, without having influence over .Net or C#? I have one idea that involves first defining one or more abstract types (interfaces such as INumeric - or more abstract than that) and then defining structs that implement these and wrap types such as int while providing operations that return the new type (e.g. Integer32 : INumeric; where addition would be defined as public Integer32 Add(Integer32 other) { return Return(Value + other.Value); } I am somewhat afraid of the execution speed of this code but at least it is abstract. No operator overloading goodness... Any other ideas? .Net doesn't look like a viable long-term platform if it cannot have this kind of abstraction I think - and be efficient about it. Abstraction is reuse.

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• client-server syncing methodology [theoretical]

  - by Kenneth Ballenegger

  I'm in the progress of building an web-app that syncs with an iOS client. I'm currently tackling trying to figure out how to go about about syncing. I've come up with following two directions: I've got a fairly simple server web-app with a list of items. They are ordered by date modified and as such syncing the order does not matter. One direction I'm considering is to let the client deal with syncing. I've already got an API that lets the client get the data, as well as do certain actions on it, such as update, add or remove single items. I was considering: 1) on each sync asking the server for all items modified since the last successful sync and updating the local records based on what's returned by the server, and 2) building a persistent queue of create / remove / update requests on the client, and keeping them until confirmation by the server. The risk with this approach is that I'm basically asking each side to send changes to the other side, hoping it works smoothly, but risking a diversion at some point. This would probably be more bandwidth-efficient, though. The other direction I was considering was a more traditional model. I would have a "sync" process in which the client would send its whole list to the server (or a subset since last modified sync), the server would update the data on the server (by fixing conflicts by keeping the last modified item, and keeping deleted items with a deleted = 1 field), and the server would return an updated list of items (since last successful sync) which the client would then replace its data with. Thoughts?

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• Opengl Iphone SDK: How to tell if you're touching an object on screen?

  - by TheGambler

  First is my touchesBegan function and then the struct that stores the values for my object. I have an array of these objects and I'm trying to figure out when I touch the screen if I'm touching an object on the screen. I don't know if I need to do this by iterating through all my objects and figure out if I'm touching an object that way or maybe there is an easier more efficient way. How is this usually handled? -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{ [super touchesEnded:touches withEvent:event]; UITouch* touch = ([touches count] == 1 ? [touches anyObject] : nil); CGRect bounds = [self bounds]; CGPoint location = [touch locationInView:self]; location.y = bounds.size.height - location.y; float xTouched = location.x/20 - 8 + ((int)location.x % 20)/20; float yTouched = location.y/20 - 12 + ((int)location.y % 20)/20; } typedef struct object_tag // Create A Structure Called Object { int tex; // Integer Used To Select Our Texture float x; // X Position float y; // Y Position float z; // Z Position float yi; // Y Increase Speed (Fall Speed) float spinz; // Z Axis Spin float spinzi; // Z Axis Spin Speed float flap; // Flapping Triangles :) float fi; // Flap Direction (Increase Value) } object;

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• mod_cgi , mod_fastcgi, mod_scgi , mod_wsgi, mod_python, FLUP. I don't know how many more. what is mo

  - by claws

  I recently learnt Python. I liked it. I just wanted to use it for web development. This thought caused all the troubles. But I like these troubles :) Coming from PHP world where there is only one way standardized. I expected the same and searched for python & apache. http://stackoverflow.com/questions/449055/setting-up-python-on-windows-apache says Stay away from mod_python. One common misleading idea is that mod_python is like mod_php, but for python. That is not true. So what is equivalent of mod_php in python? I need little clarification on this one http://stackoverflow.com/questions/219110/how-python-web-frameworks-wsgi-and-cgi-fit-together CGI, FastCGI and SCGI are language agnostic. You can write CGI scripts in Perl, Python, C, bash, or even Assembly :). So, I guess mod_cgi , mod_fastcgi, mod_scgi are their corresponding apache modules. Right? WSGI is some kind of optimized/improved inshort an efficient version specifically designed for python language only. In order to use this mod_wsgi is a way to go. right? This leaves out mod_python. What is it then? Apache - mod_fastcgi - FLUP (via CGI protocol) - Django (via WSGI protocol) Flup is another way to run with wsgi for any webserver that can speak FCGI, SCGI or AJP What is FLUP? What is AJP? How did Django come in the picture? These questions raise quetions about PHP. How is it actually running? What technology is it using? mod_php & mod_python what are the differences? In future if I want to use Perl or Java then again will I have to get confused? Kindly can someone explain things clearly and give a Complete Picture.

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• How to read LARGE Sqlite file to be copied into Android emulator, or device from assets folder?

  - by Peter SHINe ???

  I guess many people already read this article: Using your own SQLite database in Android applications: http://www.reigndesign.com/blog/using-your-own-sqlite-database-in-android-applications/comment-page-2/#comment-12368 However it's keep bringing IOException at while ((length = myInput.read(buffer))>0){ myOutput.write(buffer, 0, length); } I’am trying to use a large DB file. It’s as big as 8MB I built it using sqlite3 in Mac OS X, inserted UTF-8 encoded strings (for I am using Korean), added android_meta table with ko_KR as locale, as instructed above. However, When I debug, it keeps showing IOException at length=myInput.read(buffer) I suspect it’s caused by trying to read a big file. If not, I have no clue why. I tested the same code using much smaller text file, and it worked fine. Can anyone help me out on this? I’ve searched many places, but no place gave me the clear answer, or good solution. Good meaning efficient or easy. I will try use BufferedInput(Output)Stream, but if the simpler one cannot work, I don’t think this will work either. Can anyone explain the fundamental limits in file input/output in Android, and the right way around it, possibly? I will really appreciate anyone’s considerate answer. Thank you. WITH MORE DETAIL: private void copyDataBase() throws IOException{ //Open your local db as the input stream InputStream myInput = myContext.getAssets().open(DB_NAME); // Path to the just created empty db String outFileName = DB_PATH + DB_NAME; //Open the empty db as the output stream OutputStream myOutput = new FileOutputStream(outFileName); //transfer bytes from the inputfile to the outputfile byte[] buffer = new byte[1024]; int length; while ((length = myInput.read(buffer))>0){ myOutput.write(buffer, 0, length); } //Close the streams myOutput.flush(); myOutput.close(); myInput.close(); }

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• how to handle multiple profiles per user?

  - by Scott Willman

  I'm doing something that doesn't feel very efficient. From my code below, you can probably see that I'm trying to allow for multiple profiles of different types attached to my custom user object (Person). One of those profiles will be considered a default and should have an accessor from the Person class. Can this be done better? from django.db import models from django.contrib.auth.models import User, UserManager class Person(User): public_name = models.CharField(max_length=24, default="Mr. T") objects = UserManager() def save(self): self.set_password(self.password) super(Person, self).save() def _getDefaultProfile(self): def_teacher = self.teacher_set.filter(default=True) if def_teacher: return def_teacher[0] def_student = self.student_set.filter(default=True) if def_student: return def_student[0] def_parent = self.parent_set.filter(default=True) if def_parent: return def_parent[0] return False profile = property(_getDefaultProfile) def _getProfiles(self): # Inefficient use of QuerySet here. Tolerated because the QuerySets should be very small. profiles = [] if self.teacher_set.count(): profiles.append(list(self.teacher_set.all())) if self.student_set.count(): profiles.append(list(self.student_set.all())) if self.parent_set.count(): profiles.append(list(self.parent_set.all())) return profiles profiles = property(_getProfiles) class BaseProfile(models.Model): person = models.ForeignKey(Person) is_default = models.BooleanField(default=False) class Meta: abstract = True class Teacher(BaseProfile): user_type = models.CharField(max_length=7, default="teacher") class Student(BaseProfile): user_type = models.CharField(max_length=7, default="student") class Parent(BaseProfile): user_type = models.CharField(max_length=7, default="parent")

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• MySQL ORDER BY DESC is fast but ASC is very slow

  - by Pepper

  Hello, I'm completely stumped on this one. For some reason when I sort this query by DESC it's super fast, but if sorted by ASC it's extremely slow. This takes about 150 milliseconds: SELECT posts.id FROM posts USE INDEX (published) WHERE posts.feed_id IN ( 4953,622,1,1852,4952,76,623,624,10 ) ORDER BY posts.published DESC LIMIT 0, 50; This takes about 32 seconds: SELECT posts.id FROM posts USE INDEX (published) WHERE posts.feed_id IN ( 4953,622,1,1852,4952,76,623,624,10 ) ORDER BY posts.published ASC LIMIT 0, 50; The EXPLAIN is the same for both queries. id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE posts index NULL published 5 NULL 50 Using where I've tracked it down to "USE INDEX (published)". If I take that out it's the same performance both ways. But the EXPLAIN shows the query is less efficient overall. id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE posts range feed_id feed_id 4 \N 759 Using where; Using filesort And here's the table. CREATE TABLE `posts` ( `id` int(20) NOT NULL AUTO_INCREMENT, `feed_id` int(11) NOT NULL, `post_url` varchar(255) NOT NULL, `title` varchar(255) NOT NULL, `content` blob, `author` varchar(255) DEFAULT NULL, `published` int(12) DEFAULT NULL, `updated` datetime NOT NULL, `created` datetime NOT NULL, PRIMARY KEY (`id`), UNIQUE KEY `post_url` (`post_url`,`feed_id`), KEY `feed_id` (`feed_id`), KEY `published` (`published`) ) ENGINE=InnoDB AUTO_INCREMENT=196530 DEFAULT CHARSET=latin1; Is there a fix for this? Thanks!

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• Google App Engine - Caching generated HTML

  - by Alexander

  I have written a Google App Engine application that programatically generates a bunch of HTML code that is really the same output for each user who logs into my system, and I know that this is going to be in-efficient when the code goes into production. So, I am trying to figure out the best way to cache the generated pages. The most probable option is to generate the pages and write them into the database, and then check the time of the database put operation for a given page against the time that the code was last updated. Then, if the code is newer than the last put to the database (for a particular HTML request), new HTML will be generated and served, and cached to the database. If the code is older than the last put to the database, then I will just get the HTML direct from the database and serve it (therefore avoiding all the CPU wastage of generating the HTML). I am not only looking to minimize load times, but to minimize CPU usage. However, one issue that I am having is that I can't figure out how to programatically check when the version of code uploaded to the app engine was updated. I am open to any suggestions on this approach, or other approaches for caching generated html. Note that while memcache could help in this situation, I believe that it is not the final solution since I really only need to re-generate html when the code is updated (as opposed to every time the memcache expires). Kind Regards, and thank you in advance for any suggestions you may be able to offer. -Alex

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• Social Network News Feed Database & Design

  - by pws5068

  I'm designing a News Feed system using PHP/MySQL similar to facebook's. I have asked a similar question before but now I've changed the design and I'm looking for feedback. Example Notifications: User_A commented on User_B's new album. "Hey man nice picture!" User_B added a new Photo to [his/her] profile. [show photo thumbnail] Initially, I implemented this using excessive columns for Obj1:Type1 | Obj2:Type2 | etc.. Now the design is set up using a couple special keywords, and actor/receiver relationships. My database is designed for efficiency - using a table of messages joined on a table containing userid,actionid,receiverid,receiverObjectTypeID, Here's a condensed version of what it will look like once joined: News_ID | User_ID | Message | Timestamp 2643 A %a commented on %o's new %r. SomeTimestamp 2644 B %a added a new %r to [his/her] profile. SomeTimestamp %a = the User_ID of the person doing the action %r = the receiving object %o = the owner of the receiving object (for example the owner of the album) (NULL if %r is a user) Questions: Is this a smart (efficient/scalable) way to move forward? How can I show messages like: "User_B added 4 new photos to his profile."?

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• Which is better Java programming practice for looping up to an int value: a converted for-each loop

  - by Arvanem

  Hi folks, Given the need to loop up to an arbitrary int value, is it better programming practice to convert the value into an array and for-each the array, or just use a traditional for loop? FYI, I am calculating the number of 5 and 6 results ("hits") in multiple throws of 6-sided dice. My arbitrary int value is the dicePool which represents the number of multiple throws. As I understand it, there are two options: Convert the dicePool into an array and for-each the array: public int calcHits(int dicePool) { int[] dp = new int[dicePool]; for (Integer a : dp) { // call throwDice method } } Use a traditional for loop. public int calcHits(int dicePool) { for (int i = 0; i < dicePool; i++) { // call throwDice method } } I apologise for the poor presentation of the code above (for some reason the code button on the Ask Question page is not doing what it should). My view is that option 1 is clumsy code and involves unnecessary creation of an array, even though the for-each loop is more efficient than the traditional for loop in Option 2. Thanks in advance for any suggestions you might have.

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• "Priming" a whole database in MSSQL for first-hit speed

  - by David Spillett

  For a particular apps I have a set of queries that I run each time the database has been restarted for any reason (server reboot usually). These "prime" SQL Server's page cache with the common core working set of the data so that the app is not unusually slow the first time a user logs in afterwards. One instance of the app is running on an over-specced arrangement where the SQL box has more RAM than the size of the database (4Gb in the machine, the DB is under 1.5Gb currently and unlikely to grow too much relative to that in the near future). Is there a neat/easy way of telling SQL Server to go away and load everything into RAM? It could be done the hard way by having a script scan sysobjects & sysindexes and running SELECT * FROM <table> WITH(INDEX(<index_name>)) ORDER BY <index_fields> for every key and index found, which should cause every used page to be read at least once and so be in RAM, but is there a cleaner or more efficient way? All planned instances where the database server is stopped are out-of-normal-working-hours (all the users are at most one timezone away and unlike me none of them work at silly hours) so such a process (until complete) slowing down users more than the working set not being primed at all would is not an issue.

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• Excel CSV into Nested Dictionary; List Comprehensions

  - by victorhooi

  heya, I have a Excel CSV files with employee records in them. Something like this: mail,first_name,surname,employee_id,manager_id,telephone_number [email protected],john,smith,503422,503423,+65(2)3423-2433 [email protected],george,brown,503097,503098,+65(2)3423-9782 .... I'm using DictReader to put this into a nested dictionary: import csv gd_extract = csv.DictReader(open('filename 20100331 original.csv'), dialect='excel') employees = dict([(row['employee_id'], row) for row in gp_extract]) Is the above the proper way to do it - it does work, but is it the Right Way? Something more efficient? Also, the funny thing is, in IDLE, if I try to print out "employees" at the shell, it seems to cause IDLE to crash (there's approximately 1051 rows). 2. Remove employee_id from inner dict The second issue issue, I'm putting it into a dictionary indexed by employee_id, with the value as a nested dictionary of all the values - however, employee_id is also a key:value inside the nested dictionary, which is a bit redundant? Is there any way to exclude it from the inner dictionary? 3. Manipulate data in comprehension Thirdly, we need do some manipulations to the imported data - for example, all the phone numbers are in the wrong format, so we need to do some regex there. Also, we need to convert manager_id to an actual manager's name, and their email address. Most managers are in the same file, while others are in an external_contractors CSV, which is similar but not quite the same format - I can import that to a separate dict though. Are these two items things that can be done within the single list comprehension, or should I use a for loop? Or does multiple comprehensions work? (sample code would be really awesome here). Or is there a smarter way in Python do it? Cheers, Victor

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• Converting an int64 value to a Number object in JavaScript

  - by Matt

  I have a COM object which has a method that returns an unsigned int64 (VT_UI8) value. We have an HTML page which contains some JavaScript which can load the COM object and make the call to that method, to retrieve the value as such: var foo = MyCOMObject.GetInt64Value(); This value can easily be displayed to the user in a message dialog using: alert(foo); or displayed on the page by: document.getElementById('displayToUser').innerHTML = foo; However, we cannot use this value as a Number (e.g. if we try to multiply it by 2) without the page throwing "Number expected" errors. If we check "typeof(foo)" it returns "unknown". I've found a workaround for this by doing the following: document.getElementById('displayToUser').innerHTML = foo; var bar = parseInt(document.getElementById('displayToUser').innerHTML); alert(bar*2); What I need to know is how to make that process more efficient. Specifically, is there a way to cast foo to a String explicitly, rather than having to set some document element's innerHTML to foo and then retrieve it from that. I wouldn't mind calling something like: alert(parseInt((string)foo) * 2); Even better would be if there is a way to directly convert the int64 to a Number, without going through the String conversion, but I hold out less hope for that.

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• Django stupid mark_safe?

  - by Mark

  I wrote this little function for writing out HTML tags: def html_tag(tag, content=None, close=True, attrs={}): lst = ['<',tag] for key, val in attrs.iteritems(): lst.append(' %s="%s"' % (key, escape_html(val))) if close: if content is None: lst.append(' />') else: lst.extend(['>', content, '</', tag, '>']) else: lst.append('>') return mark_safe(''.join(lst)) Which worked great, but then I read this article on efficient string concatenation (I know it doesn't really matter for this, but I wanted consistency) and decided to update my script: def html_tag(tag, body=None, close=True, attrs={}): s = StringIO() s.write('<%s'%tag) for key, val in attrs.iteritems(): s.write(' %s="%s"' % (key, escape_html(val))) if close: if body is None: s.write(' />') else: s.write('>%s</%s>' % (body, tag)) else: s.write('>') return mark_safe(s.getvalue()) But now my HTML get escaped when I try to render it from my template. Everything else is exactly the same. It works properly if I replace the last line with return mark_safe(unicode(s.getvalue())). I checked the return type of s.getvalue(). It should be a str, just like the first function, so why is this failing?? Also fails with SafeString(s.getvalue()) but succeeds with SafeUnicode(s.getvalue()). I'd also like to point out that I used return mark_safe(s.getvalue()) in a different function with no odd behavior.

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• Design suggestion for expression tree evaluation with time-series data

  - by Lirik

  I have a (C#) genetic program that uses financial time-series data and it's currently working but I want to re-design the architecture to be more robust. My main goals are: sequentially present the time-series data to the expression trees. allow expression trees to access previous data rows when needed. to optimize performance of the data access while evaluating the expression trees. keep a common interface so various types of data can be used. Here are the possible approaches I've thought about: I can evaluate the expression tree by passing in a data row into the root node and let each child node use the same data row. I can evaluate the expression tree by passing in the data row index and letting each node get the data row from a shared DataSet (currently I'm passing the row index and going to multiple synchronized arrays to get the data). Hybrid: an immutable data set is accessible by all of the expression trees and each expression tree is evaluated by passing in a data row. The benefit of the first approach is that the data row is being passed into the expression tree and there is no further query done on the data set (which should increase performance in a multithreaded environment). The drawback is that the expression tree does not have access to the rest of the data (in case some of the functions need to do calculations using previous data rows). The benefit of the second approach is that the expression trees can access any data up to the latest data row, but unless I specify what that row is, I'll have to iterate through the rows and figure out which one is the last one. The benefit of the hybrid is that it should generally perform better and still provide access to the earlier data. It supports two basic "views" of data: the latest row and the previous rows. Do you guys know of any design patterns or do you have any tips that can help me build this type of system? Should I use a DataSet to hold and present the data, or are there more efficient ways to present rows of data while maintaining a simple interface? FYI: All of my code is written in C#.

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• "Work stealing" vs. "Work shrugging"?

  - by John

  Why is it that I can find lots of information on "work stealing" and nothing on "work shrugging" as a dynamic load-balancing strategy? By "work-shrugging" I mean busy processors pushing excessive work towards less loaded neighbours rather than idle processors pulling work from busy neighbours ("work-stealing"). I think the general scalability should be the same for both strategies. However I believe that it is much more efficient for busy processors to wake idle processors if and when there is definitely work for them to do than having idle processors spinning or waking periodically to speculatively poll all neighbours for possible work. Anyway a quick google didn't show up anything under the heading of "Work Shrugging" or similar so any pointers to prior-art and the jargon for this strategy would be welcome. Clarification/Confession In more detail:- By "Work Shrugging" I actually envisage the work submitting processor (which may or may not be the target processor) being responsible for looking around the immediate locality of the preferred target processor (based on data/code locality) to decide if a near neighbour should be given the new work instead because they don't have as much work to do. I am talking about an atomic read of the immediate (typically 2 to 4) neighbours' estimated q length here. I do not think this is any more coupling than implied by the thieves polling & stealing from their neighbours - just much less often - or rather - only when it makes economic sense to do so. (I am assuming "lock-free, almost wait-free" queue structures in both strategies). Thanks.

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• Get Last Friday of Month in Java

  - by Nick Klauer

  I am working on a project where the requirement is to have a date calculated as being the last Friday of a given month. I think I have a solution that only uses standard Java, but I was wondering if anyone knew of anything more concise or efficient. Below is what I tested with for this year: for (int month = 0; month < 13; month++) { GregorianCalendar d = new GregorianCalendar(); d.set(d.MONTH, month); System.out.println("Last Week of Month in " + d.getDisplayName(d.MONTH, Calendar.LONG, Locale.ENGLISH) + ": " + d.getLeastMaximum(d.WEEK_OF_MONTH)); d.set(d.DAY_OF_WEEK, d.FRIDAY); d.set(d.WEEK_OF_MONTH, d.getActualMaximum(d.WEEK_OF_MONTH)); while (d.get(d.MONTH) > month || d.get(d.MONTH) < month) { d.add(d.WEEK_OF_MONTH, -1); } Date dt = d.getTime(); System.out.println("Last Friday of Last Week in " + d.getDisplayName(d.MONTH, Calendar.LONG, Locale.ENGLISH) + ": " + dt.toString()); }

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• algorithm || method to write prog

  - by fatai

  I am one of the computer science student. My wonder is everyone solve problem with different or same method, but actually I dont know whether they use method or I dont know whether there are such common method to approach problem. All teacher give us problem which in simple form sometimes, but they dont introduce any approach or method(s) so that we can first choose method then apply that one to problem , afterward find solution then write code. I have found one method when I failed the course, More accurately, When I counter problem in language , I will get more paper and then ; first, input/ output step ; my prog will take this / these there argument(s) and return namely X , ex : in c, input length is not known and at same type , so I must use pointer desired output is in form of package , so use structure second, execution part ; in that step , I am writing all step which are goes to final output ex : in python ; 1.) [ + , [- , 4 , [ * , 1 , 2 ]], 5] 2.) [ + , [- , 4 , 2 ],5 ] 3.) [ + , 2 , 5] 4.) 7 ==> return 7 third, I will write test code ex : in c++ input : append 3 4 5 6 vector_x remove 0 1 desired output vector_x holds : 5 6 But now, I wonder other method ; used to construct class :::: for c++ , python, java used to communicate classes / computers used for solving embedded system problem ::::: for c Why I wonder , because I learn if you dont costruct algorithm on paper, you may achieve your goal. Like no money no lunch , I can say no algorithm no prog therefore , feel free when you write your own method , a way which is introduced by someone else but you are using and you find it is so efficient

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• PHP OOP: Providing Domain Entities with "Identity"

  - by sunwukung

  Bit of an abstract problem here. I'm experimenting with the Domain Model pattern, and barring my other tussles with dependencies - I need some advice on generating Identity for use in an Identity Map. In most examples for the Data Mapper pattern I've seen (including the one outlined in this book: http://apress.com/book/view/9781590599099) - the user appears to manually set the identity for a given Domain Object using a setter: $UserMapper = new UserMapper; //returns a fully formed user object from record sets $User = $UserMapper->find(1); //returns an empty object with appropriate properties for completion $UserBlank = $UserMapper->get(); $UserBlank->setId(); $UserBlank->setOtherProperties(); Now, I don't know if I'm reading the examples wrong - but in the first $User object, the $id property is retrieved from the data store (I'm assuming $id represents a row id). In the latter case, however, how can you set the $id for an object if it has not yet acquired one from the data store? The problem is generating a valid "identity" for the object so that it can be maintained via an Identity Map - so generating an arbitrary integer doesn't solve it. My current thinking is to nominate different fields for identity (i.e. email) and demanding their presence in generating blank Domain Objects. Alternatively, demanding all objects be fully formed, and using all properties as their identity...hardly efficient. (Or alternatively, dump the Domain Model concept and return to DBAL/DAO/Transaction Scripts...which is seeming increasingly elegant compared to the ORM implementations I've seen...)

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