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• Graph search problem with route restrictions

  - by Darcara

  I want to calculate the most profitable route and I think this is a type of traveling salesman problem. I have a set of nodes that I can visit and a function to calculate cost for traveling between nodes and points for reaching the nodes. The goal is to reach a fixed known score while minimizing the cost. This cost and rewards are not fixed and depend on the nodes visited before. The starting node is fixed. There are some restrictions on how nodes can be visited. Some simplified examples include: Node B can only be visited after A After node C has been visited, D or E can be visited. Visiting at least one is required, visiting both is permissible. Z can only be visited after at least 5 other nodes have been visited Once 50 nodes have been visited, the nodes A-M will no longer reward points Certain nodes can (and probably must) be visited multiple times Currently I can think of only two ways to solve this: a) Genetic Algorithms, with the fitness function calculating the cost/benefit of the generated route b) Dijkstra search through the graph, since the starting node is fixed, although the large number of nodes will probably make that not feasible memory wise. Are there any other ways to determine the best route through the graph? It doesn't need to be perfect, an approximated path is perfectly fine, as long as it's error acceptable. Would TSP-solvers be an option here?

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• TCP Scanner Python MultiThreaded

  - by user1473508

  I'm trying to build a small tcp scanner for a netmask. The code is as follow: import socket,sys,re,struct from socket import * host = sys.argv[1] def RunScanner(host): s = socket(AF_INET, SOCK_STREAM) s.connect((host,80)) s.settimeout(0.1) String = "GET / HTTP/1.0" s.send(String) data = s.recv(1024) if data: print "host: %s have port 80 open"%(host) Slash = re.search("/", str(host)) if Slash : netR,_,Wholemask = host.partition('/') Wholemask = int(Wholemask) netR = struct.unpack("!L",inet_aton(netR))[0] for host in (inet_ntoa(struct.pack("!L", netR+n)) for n in range(0, 1<<32-Wholemask)): try: print "Doing host",host RunScanner(host) except: pass else: RunScanner(host) To launch : python script.py 10.50.23.0/24 The problem I'm having is that even with a ridiculous low settimeout value set, it takes ages to cover the 255 ip addresses since most of them are not assigned to a machine. How can i make a way faster scanner that wont get stuck if the port is close.MultiThreading ? Thanks !

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• Visual C++ function suddenly 170x slower

  - by Mikael

  For the past few months I've been working on a Visual C++ project to take images from cameras and process them. Up until today this has taken about 65 ms to update the data but now it has suddenly increased significantly. What happens is: I launch my program and for the first 30 or so iterations it performs as expected, then suddenly the loop time increases from 65 ms to 250 ms. The odd thing is, after timing each function I found out that the part of the code which is causing the slowdown is fairly basic and has not been modified in over a month. The data which goes into it is unchanged and identical every iteration but the execution time which is initially less than 1 ms suddenly increases to 170 ms while the rest of the code is still performing as expected (time-wise). Basically, I am calling the same function over and over, for the first 30 calls it performs as it should, after that it slows down for no apparent reason. It might also be worth noting that it is a sudden change in execution time, not a gradual increase. What could be causing this? The code is leaking some memory (~50 kb/s) but not nearly enough to warrant a sudden 4x slowdown. If anyone has any ideas I'd love to hear them!

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• INSERT INTO ... SELECT ... vs dumping/loading a file in MySQL

  - by Daniel Huckstep

  What are the implications of using a INSERT INTO foo ... SELECT FROM bar JOIN baz ... style insert statement versus using the same SELECT statement to dump (bar, baz) to a file, and then insert into foo by loading the file? In my messing around, I haven't seen a huge difference. I would assume the former would use more memory, but the machine that this runs on has 8GB of RAM, and I never even see it go past half used. Are there any huge (or long term) performance implications that I'm not seeing? Advantages/disadvantages of either?

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• SQL Server 2008 - Get Latest Record from Joined Table

  - by user336786

  Hello, I have a SQL Server 2008 database. This database has two tables called Customer and Order. These tables are defined as follows: Customer -------- ID, First Name, Last Name Order ----- ID, CustomerID, Date, Description I am trying to write a query that returns all of the customers in my database. If the user has placed at least one order, I want to return the information associated with the most recent order placed. Currently, I have the following: SELECT * FROM Customer c LEFT OUTER JOIN Order o ON c.[ID]=o.[CustomerID] As you can imagine, this will return all of the orders associated with a customer. In reality though, I only want the most recent one. How do I do this in SQL? Thank you!

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• php and SQL_CALC_FOUND_ROWS

  - by Lizard

  I am trying to add the SQL_CALC_FOUND_ROWS into a query (Please note this isn't for pagination) please note I am trying to add this to a cakePHP query the code I currently have is below: return $this->find('all', array( 'conditions' => $conditions, 'fields'=>array('SQL_CALC_FOUND_ROWS','Category.*','COUNT(`Entity`.`id`) as `entity_count`'), 'joins' => array('LEFT JOIN `entities` AS Entity ON `Entity`.`category_id` = `Category`.`id`'), 'group' => '`Category`.`id`', 'order' => $sort, 'limit'=>$params['limit'], 'offset'=>$params['start'], 'contain' => array('Domain' => array('fields' => array('title'))) )); Note the 'fields'=>array('SQL_CALC_FOUND_ROWS',' this obviously doesn't work as It tries to apply the SQL_CALC_FOUND_ROWS to the table e.g. SELECTCategory.SQL_CALC_FOUND_ROWS, Is there anyway of doing this? Any help would be greatly appreciated, thanks.

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• Facebook: Requires a valid user is specified (either via the session or via the API parameter for specifying the user.

  - by Stoic

  Hey Everyone, I am receiving this error: Requires a valid user is specified (either via the session or via the API parameter for specifying the user. when I am trying to utilize Facebook's FB.api with JS SDK for method: users.hasAppPermission I am constantly receiving this error, for any uid I pass on. Here is my code: $(document).ready(function() { var perms_requested = <?php echo PERMS;?>; var user_id = <?=$user_id;?>; $('#perms_check').html(loading); ask_for_perms(perms_requested, function(data) { $('#perms_check').html(data); }); function ask_for_perms(perms_requested,cb) { var request = []; $.each(perms_requested,function(i,permission) { FB.api({ method: 'users.hasAppPermission', ext_perm: permission, uid: user_id }, function(response) { if (response == 0) request.push(permission); if (i == perms_requested.length - 1) cb(request.join(', ')); }); }); } }); Also, I am utilizing nearly the same code in some other part of the same application, and I am getting fine results with that.

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• SQL: How to use a column that was just added

  - by sbenderli

  I am trying to add 2 columns and then I would like to set some values to them but I get a compile-error saying the column does not exist. I am using the following script: IF NOT EXISTS (select column_name from INFORMATION_SCHEMA.columns where table_name = 'SYSTM_FRM' and column_name = 'SF_Ip_TXT') ALTER TABLE SYSTM_FRM add SF_Ip_TXT NVARCHAR(20) IF NOT EXISTS (select column_name from INFORMATION_SCHEMA.columns where table_name = 'SYSTM_FRM' and column_name = 'SF_Port_NUM') ALTER TABLE SYSTM_FRM add SF_Port_NUM int Update dbo.SYSTM_FRM SET dbo.SYSTM_FRM.SF_Ip_TXT = dbo.FRM.FRM_Ip_TXT, dbo.SYSTM_FRM.SF_Port_NUM = dbo.FRM.FRM_Port_NUM FROM dbo.FRM INNER JOIN dbo.SYSTM_FRM ON dbo.FRM.FRM_RCRD_NUM = dbo.SYSTM_FRM.SF_FrameRecord_NUM Is there any way to use a column that I am adding in the same script?

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• What is PHP like as a programming language?

  - by seanlinmt

  I am not really familiar with PHP, but I get the impression that it is like JavaScript (syntax-wise). What are the benefits of a dynamically typed language, when compared to a strongly typed language like C# or Java, and how would this help in the context of web development? What would make a dynamically typed language so attractive? Or, does the popularity of PHP have more to do with it being free? Okay, I think I better give a little more background to get more meaningful answers, because I am not wanting a flame war. I come from a C background, and when I moved into C# and Visual Studio. Having code completion, integration with an SQL database, huge existing class libraries and easy to access documentation, as well as new tools such as LINQ and ReSharper was like heaven. I didn't enjoy JavaScript before JQuery, but now I love it as well. Recently, I ported a PHP project over to C# and I used Zend to help me debug and understand more while porting - instead of maintaining two code streams. That also cut down on the cost of the server and maintenance. Getting into PHP would be nice. I think that Visual Studio has spoiled me - but again Eclipse is also equally spoiling. It would be nice to have an answer from someone who has experience developing both under PHP and .NET.

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• scope of variables java

  - by qxc

  Is a variable inside the main, a public variable? public static void main(String[] args) { ......... for(int i=0;i<threads.length;i++) try { threads[i].join(); } catch (InterruptedException e) { e.printStackTrace(); } long time=0; .... } i and time are they both public variables? Of course if my reasoning is correct, also any variable belonging to a public method should be considered public.. am i right? Thanks

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• what's wrong with this code..

  - by rockers

  $('#PbtnSubmit').click(function() { if ($("#PricingEditExceptions input:checkbox:checked").length > 0) { var chec = $('#PricingEditExceptions input[type=checkbox]:checked'); var strIDs = chec.map(function() { return $(this).val(); }).get().join(","); alert(PMstrIDs); $('#1_exceptiontypes').attr('value', exceptiontypes) $('#1_PMstrIDs').attr('value', PMstrIDs); } else { alert("please select atleast one exception"); return false; } }); var checked = $('#PricingEditExceptions input[type=checkbox]:checked'); this code returns correct value in Firefox but not in IE8.. is that something need to change? why I am not getting all the checked checkboxes in IE8? please can anybody help me out? thanks

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• Object for storing strings in Python

  - by evg

  class MyWriter: def __init__(self, stdout): self.stdout = stdout self.dumps = [] def write(self, text): self.stdout.write(smart_unicode(text).encode('cp1251')) self.dumps.append(text) def close(self): self.stdout.close() writer = MyWriter(sys.stdout) save = sys.stdout sys.stdout = writer I use self.dumps list to store data obtained from prints. Is there a more convenient object for storing string lines in memory? Ideally I want dump it to one big string. I can get it like this "\n".join(self.dumps) from code above. May be it's better to just concatenate strings - self.dumps += text?

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• MySQL - JOINS (excepts)

  - by user2529899

  I'm trying to find 2 different result via JOINS. Table look like; SELECT id,member_id,registered_year FROM records; I can listing which members registered in 2012 and also in 2013 with; SELECT member_id FROM records a INNER JOIN records b ON a.member_id=b.member_id WHERE a.registered_year='2013' AND b.registered_year='2012'; But I can't list revers of It. How can I list which members were registered in 2012 but not in 2013? Thnx in advance.

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• SQL Modify question

  - by Jeff

  I need to replace a lot of values for a Table in SQL if the inactivity is greater then 30 days. I have UPDATE VERSION SET isActive = 0 WHERE customerNo = ( SELECT c.VersionNo FROM Activity b INNER JOIN VERSION c ON b.VersionNo = c.VersionNo WHERE (Months_between(sysdate, b.Activitye) > 30) ); It only works for one value though, if there is more then one returned it fails. What am I missing here? If someone could educate me on what is going on, I'd also appreciate it.

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• deleting and reusing a temp table in a stored precedures

  - by Sheagorath

  Hi I need to SELECT INTO a temp table multiple times with a loop but I just can't do it, because after the table created( in SELECT into you can't simply drop the table at the end of the loop because you can't delete a table and create it again in the same batch. so how can I delete a table in a stored procedure and create it again? here is a snippet of where I am actualy using the temp table which is supposed to be a pivoting algorithm: WHILE @offset<@NumDays BEGIN SELECT bg.*, j.ID, j.time, j.Status INTO #TEMP1 FROM #TEMP2 AS bg left outer join PersonSchedule j on bg.PersonID = j.PersonID and bg.TimeSlotDateTime = j.TimeSlotDateTime and j.TimeSlotDateTime = @StartDate + @offset DROP TABLE #TEMP2; SELECT * INTO #TEMP2 FROM #TEMP1 DROP TABLE #TEMP1 SET @offset = @offset + 1 END

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• Best way to implement some type of ITaggable interface

  - by Jack

  I've got a program I'm creating that reports on another certain programs backup xml files. I've gotten to the point where I need to implement some type of ITaggable interface - but am unsure how to go about it code wise. My idea is that each item (BackupClient, BackupVersion, and BackupFile) should implement an ITaggable interface for highlighting old, out of date, or non-existent files in their HTML or Excel report. The user will be able to specify tags in the settings. My question is this, how can a user dynamically specify a "tag" such as File Date 3 days old? - Background Color = Red. Actually I guess my question is more, how can I, the programmer, implement this dynamically? I was thinking Expression trees, but am unsure this is the way to go as I havn't studied them much. I know my ITaggable interface would have methods such as AddTag(T tag), RemoveTag(T tag), but what exactly specifies the criteria for the tag to be added? I realize this may be subjective, and can be marked as wiki if need be, but I truly am stuck. Any input would be greatly helpful!

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• C++ and virtual methods overriding

  - by silent

  Sorry for this stupid question, but I can't find an answer by myself, I'm too new in C++ :( class DBObject : public QObject { ... protected: virtual QString tableName() { return ""; }; }; class DBUserObject : public DBObject { ... protected: virtual QString tableName() { return "profiles"; }; }; And I have this code in parent: bool DBObject::load(quint32 id) { QString query = QString("select %1 from %2 where id = :id") .arg(fieldList().join(",")) .arg(tableName()); <--- here is trouble ... } So I'm trying to execute: DBUserObject user; user.load(3); But in result I have a query with empty table name cause tableName() method returns empty string. Why not "profiles"?

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• Where do you find images and graphics designers for your softwares ?

  - by ereOn

  Hi, As a programmer, I'm sure some of you already experienced the same problem: You create a good software (free, open-source, or for friend-only diffusion, whatever) relying on good code and good ideas but since you're a programmer and not an image designer, your program looks just bad. While it seems pretty easy to find motivated developpers to join for free an open-source project, it seems quite hard to find a single free graphic designer. What free and good resources do you usually use for your programs/websites ? Do you have any cool tip that you're willing to share ? Do you know any place where to find people involved into graphic design willing to participate to open-source projects ?

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• How do you make long SQL invoked from other code readable?

  - by Artem

  This is a very open question, but I think it can be very beneficial for SQL readability. So you have a Java program, and you are trying to call a monster SQL statement from it, with many subqueries and joins. The starting point for my question is a string constant like this: static string MONSTER_STATEMENT = "SELECT " + " fields" + "WHERE "+ " fieldA = (SELECT a FROM TableC) " + "AND fieldB IN (%s)" + "AND fieldC = %d " + "FROM " " tableA INNER JOIN tableB ON ..."; It later gets filled using String.format and executed. What are you tricks for making this kind of stuff readable? Do you separate your inner joins. Do you indent the SQL itself inside the string? Where do you put the comments? Please share all of the tricks in your arsenal.

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• Google App Engine: Difficulty with Users API (or maybe just a Python syntax problem)

  - by Rosarch

  I have a simple GAE app that includes a login/logout link. This app is running on the dev server at the moment. The base page handler gets the current user, and creates a login/logout url appropriately. It then puts this information into a _template_data dictionary, for convenience of subclasses. class BasePage(webapp.RequestHandler): _user = users.get_current_user() _login_logout_link = None if _user: _login_logout_link = users.create_logout_url('/') else: _login_logout_link = users.create_login_url('/') _template_data = {} _template_data['login_logout_link'] = _login_logout_link _template_data['user'] = _user def render(self, templateName, templateData): path = os.path.join(os.path.dirname(__file__), 'Static/Templates/%s.html' % templateName) self.response.out.write(template.render(path, templateData)) Here is one such subclass: class MainPage(BasePage): def get(self): self.render('start', self._template_data) The login/logout link is displayed fine, and going to the correct devserver login/logout page. However, it seems to have no effect - the server still seems to think the user is logged out. What am I doing wrong here?

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• In Python, is it better to use list comprehensions or for-each loops?

  - by froadie

  Which of the following is better to use and why? Method 1: for k, v in os.environ.items() print "%s=%s" % (k, v) Method 2: print "\n".join(["%s=%s" % (k, v) for k,v in os.environ.items()]) I tend to lead towards the first as more understandable, but that might just be because I'm new to Python and list comprehensions are still somewhat foreign to me. Is the second way considered more Pythonic? I'm assuming there's no performance difference, but I may be wrong. What would be the advantages and disadvantages of these 2 techniques? (Code taken from Dive into Python)

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• Problem removing a dynamic form field in jquery

  - by rshivers

  I'm trying to remove a dynamic form field by click a button. It will also subtract whatever values it had from the total amount from my calculation. This is the code: function removeFormField(id) { var id = $(id).attr("name"); $('#target1').text($("#total" + id).map(function() { var currentValue = parseFloat(document.getElementById("currentTotal").value); var newValue = parseFloat($("#total" + id).text()); var newTotal = currentValue - newValue; document.getElementById("currentTotal").value = newTotal; return newTotal; }).get().join()); $(id).remove(); } Okay, it will do the subtraction portion of the code with no problem, this issue is with the last line to remove the field. If I comment out the rest of the code it will work, but not with the rest of the code. I know this is something simple, yet I can't seem to wrap my mind around it. Can someone please help?

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• Problem with Nulls and an UPDATE statement

  - by Dave

  UPDATE TableA SET Value = a.Value * b.AnotherValue FROM TableA AS a INNER JOIN TableB AS b WHERE (Condition is true); Here is the problem. The Value field for TableA does not allow nulls. If the calculation of a.Value * b.AnotherValue yields a null, an error is thrown. Now the question. Is there any way to tell the UPDATE to ignore the SET phase when the result of the calculation is a null and delete the record rather than updating it. This UPDATE is intended to update hundreds of records at a time but will fail if a single null is encountered. Also, please note that using the ISNULL() function and setting the Value to zero is not acceptable. I would like the record to be dropped if a null is encountered. Many thanks in advance for any help rendered.

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• Managing a list of threads

  - by Satanlike

  Hi, I have an application (.Net 3.5) which creates threads to write something to the database so that the GUI does not block. All created threads are added to a list, so that I can wait (Thread.Join) for each thread when the application is closed (maybe not all threads are finished when the application is closed, so the app must wait for them). Because of the list I get some serious problems if there are too many threads created (OutOfMemoryException). I tried removing finished threads from the list, but somehow that didn't work. Are there better ways to manage a list of threads, so I can remove them once they are finished?

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• Handling missing data

  - by soppotare

  Say I have a simple helpdesk application which logs calls made by users. I would typically have such fields in a table relating to the call e.g. CallID, Description, CustomerID etc. I Would also have a table of customers including CustomerID, Username, Password, FullName etc. Now when a user is deleted from the customers table then the inner join between the calls table and the users table to find out historically which user logged a call would produce no results. How do people usually deal with this? Have seperate customer and useraccount tables Just disable the accounts so the data is still available Record the customers name in the calls table as a seperate field. or any other methods / suggestions?

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