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  • Program structure in long running data processing python script

    - by fmark
    For my current job I am writing some long-running (think hours to days) scripts that do CPU intensive data-processing. The program flow is very simple - it proceeds into the main loop, completes the main loop, saves output and terminates: The basic structure of my programs tends to be like so: <import statements> <constant declarations> <misc function declarations> def main(): for blah in blahs(): <lots of local variables> <lots of tightly coupled computation> for something in somethings(): <lots more local variables> <lots more computation> <etc., etc.> <save results> if __name__ == "__main__": main() This gets unmanageable quickly, so I want to refactor it into something more manageable. I want to make this more maintainable, without sacrificing execution speed. Each chuck of code relies on a large number of variables however, so refactoring parts of the computation out to functions would make parameters list grow out of hand very quickly. Should I put this sort of code into a python class, and change the local variables into class variables? It doesn't make a great deal of sense tp me conceptually to turn the program into a class, as the class would never be reused, and only one instance would ever be created per instance. What is the best practice structure for this kind of program? I am using python but the question is relatively language-agnostic, assuming a modern object-oriented language features.

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  • Create static instances of a class inside said class in Python

    - by Samir Talwar
    Apologies if I've got the terminology wrong here—I can't think what this particular idiom would be called. I've been trying to create a Python 3 class that statically declares instances of itself inside itself—sort of like an enum would work. Here's a simplified version of the code I wrote: class Test: A = Test("A") B = Test("B") def __init__(self, value): self.value = value def __str__(self): return "Test: " + self.value print(str(Test.A)) print(str(Test.B)) Writing this, I got an exception on line 2 (A = Test("A")). I assume line 3 would also error if it had made it that far. Using __class__ instead of Test gives the same error. File "<stdin>", line 1, in <module> File "<stdin>", line 2, in Test NameError: name 'Test' is not defined Is there any way to refer to the current class in a static context in Python? I could declare these particular variables outside the class or in a separate class, but for clarity's sake, I'd rather not if I can help it. To better demonstrate what I'm trying to do, here's the same example in Java: public class Test { private static final Test A = new Test("A"); private static final Test B = new Test("B"); private final String value; public Test(String value) { this.value = value; } public String toString() { return "Test: " + value; } public static void main(String[] args) { System.out.println(A); System.out.println(B); } } This works as you would expect: it prints: Test: A Test: B How can I do the same thing in Python?

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  • is there a better way to write this frankenstein LINQ query that searches for values in a child tabl

    - by MRV
    I have a table of Users and a one to many UserSkills table. I need to be able to search for users based on skills. This query takes a list of desired skills and searches for users who have those skills. I want to sort the users based on the number of desired skills they posses. So if a users only has 1 of 3 desired skills he will be further down the list than the user who has 3 of 3 desired skills. I start with my comma separated list of skill IDs that are being searched for: List<short> searchedSkillsRaw = skills.Value.Split(',').Select(i => short.Parse(i)).ToList(); I then filter out only the types of users that are searchable: List<User> users = (from u in db.Users where u.Verified == true && u.Level > 0 && u.Type == 1 && (u.UserDetail.City == city.SelectedValue || u.UserDetail.City == null) select u).ToList(); and then comes the crazy part: var fUsers = from u in users select new { u.Id, u.FirstName, u.LastName, u.UserName, UserPhone = u.UserDetail.Phone, UserSkills = (from uskills in u.UserSkills join skillsJoin in configSkills on uskills.SkillId equals skillsJoin.ValueIdInt into tempSkills from skillsJoin in tempSkills.DefaultIfEmpty() where uskills.UserId == u.Id select new { SkillId = uskills.SkillId, SkillName = skillsJoin.Name, SkillNameFound = searchedSkillsRaw.Contains(uskills.SkillId) }), UserSkillsFound = (from uskills in u.UserSkills where uskills.UserId == u.Id && searchedSkillsRaw.Contains(uskills.SkillId) select uskills.UserId).Count() } into userResults where userResults.UserSkillsFound > 0 orderby userResults.UserSkillsFound descending select userResults; and this works! But it seems super bloated and inefficient to me. Especially the secondary part that counts the number of skills found. Thanks for any advice you can give. --r

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  • DDD: Enum like entities

    - by Chris
    Hi all, I have the following DB model: **Person table** ID | Name | StateId ------------------------------ 1 Joe 1 2 Peter 1 3 John 2 **State table** ID | Desc ------------------------------ 1 Working 2 Vacation and domain model would be (simplified): public class Person { public int Id { get; } public string Name { get; set; } public State State { get; set; } } public class State { private int id; public string Name { get; set; } } The state might be used in the domain logic e.g.: if(person.State == State.Working) // some logic So from my understanding, the State acts like a value object which is used for domain logic checks. But it also needs to be present in the DB model to represent a clean ERM. So state might be extended to: public class State { private int id; public string Name { get; set; } public static State New {get {return new State([hardCodedIdHere?], [hardCodeNameHere?]);}} } But using this approach the name of the state would be hardcoded into the domain. Do you know what I mean? Is there a standard approach for such a thing? From my point of view what I am trying to do is using an object (which is persisted from the ERM design perspective) as a sort of value object within my domain. What do you think? Question update: Probably my question wasn't clear enough. What I need to know is, how I would use an entity (like the State example) that is stored in a database within my domain logic. To avoid things like: if(person.State.Id == State.Working.Id) // some logic or if(person.State.Id == WORKING_ID) // some logic

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  • How do I deliver mail for wildcard addresses to a particular user/alias/program?

    - by David M
    I need to configure sendmail so that mail delivered for wildcard addresses is accepted for delivery and then delivered to a user, alias, or directly to a script. I can rewrite the envelope/headers any number of ways, but I don't know how to accept the wildcard address when it's provided in RCPT TO: Everything I've tried so far winds up with a 550 user unknown error. So here's a specific example: I want to be able to handle any address that consists of a series of digits followed by a dot followed by a word, then pipe that to a script. If the headers get rewritten, that's OK, but I need the envelope to contain the actual Delivered-To address. Here's the sort of SMTP session I need: 220 blah.foo.com ESMTP server ready; Thu, 22 Apr 2010 20:41:08 -0700 (PDT) HELO blort.foo.com 250 blah.foo.com Hello blort.foo.com [10.1.2.3], pleased to meet you MAIL FROM: <[email protected]> 250 2.1.0 <[email protected]>... Sender ok RCPT TO: <[email protected]> 250 2.1.5 <[email protected]>... Recipient ok I tried some stuff with regex maps, but I never got past 550 user unknown.

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  • Removing "Using temporary; Using filesort" from this MySQL select+join+group by query

    - by claytontstanley
    I have the following query: select t.Chunk as LeftChunk, t.ChunkHash as LeftChunkHash, q.Chunk as RightChunk, q.ChunkHash as RightChunkHash, count(t.ChunkHash) as ChunkCount from chunksubset as t join chunksubset as q on t.ID = q.ID group by LeftChunkHash, RightChunkHash And the following explain table: id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE subsets ref PRIMARY,IDIndex,SubsetIndex SubsetIndex 767 const 522014 "Using where; Using temporary; Using filesort" 1 SIMPLE subsets eq_ref PRIMARY,IDIndex,SubsetIndex PRIMARY 771 sotero.subsets.Id,const 1 "Using where; Using index" 1 SIMPLE c ref IDIndex IDIndex 4 sotero.subsets.Id 12 "Using where" 1 SIMPLE c ref IDIndex IDIndex 4 sotero.subsets.Id 12 note the "using temporary; using filesort". When this query is run, I quickly run out of RAM (presumably b/c of the temp table), and then the HDD kicks in, and the query slows to a halt. I thought it might be an index issue, so I started adding a few that sort of made sense: Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment chunks 0 PRIMARY 1 ChunkId A 17796190 NULL NULL BTREE chunks 1 ChunkHashIndex 1 ChunkHash A 243783 NULL NULL BTREE chunks 1 IDIndex 1 Id A 1483015 NULL NULL BTREE chunks 1 ChunkIndex 1 Chunk A 243783 NULL NULL BTREE chunks 1 ChunkTypeIndex 1 ChunkType A 2 NULL NULL BTREE chunks 1 chunkHashByChunkIDIndex 1 ChunkHash A 243783 NULL NULL BTREE chunks 1 chunkHashByChunkIDIndex 2 ChunkId A 17796190 NULL NULL BTREE chunks 1 chunkHashByChunkTypeIndex 1 ChunkHash A 243783 NULL NULL BTREE chunks 1 chunkHashByChunkTypeIndex 2 ChunkType A 261708 NULL NULL BTREE chunks 1 chunkHashByIDIndex 1 ChunkHash A 243783 NULL NULL BTREE chunks 1 chunkHashByIDIndex 2 Id A 17796190 NULL NULL BTREE But still using the temporary table. The db engine is MyISAM. How can I get rid of the using temporary; using filesort in this query? Just changing to InnoDB w/o explaining the underlying cause is not a particularly satisfying answer. Besides, if the solution is to just add the proper index, then that's much easier than migrating to another db engine.

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  • Ways of breaking down SQL transactional/call data into reports -- 'square data'?

    - by RizwanK
    I've got a large database of call-traffic information (although the question could be answered with any generic data set.) For instance, a row contains : call endpoint server (endpoint_name) call endpoint status (sip_disconnect_reason) call destination (destination) call completed (duration) [duration 0 is completed] call account group (account_group) It's pretty easy to run SQL reports against the data, i.e. select count(*), endpoint_name from calls where duration0 group by endpoint_name select count(*),destination from calls where blah group by destination I've been calling this filtering or breakdown reports (I get the number of calls per carrier, etc.). Add another breakdown, and you've got two breakdowns, a la select count(*), endpoint_name, sip_disconnect_reason from calls where duration=0 group by endpoint_name, sip_disconnect_reason Of course, if you keep adding breakdowns, you end up making super-large reports and slicing your data so thin that you can't extract any trends from it. So my question is this : Is there a name for this sort of method of report writing? (I've heard words like squares, slicing and breakdown reports applied to them) --- I'm looking for a Python/Reporting toolkit that I can use to make these easier to generate for my end users. aside : Are there other ways of representing transactional data that might be useful rather than the above method? Thanks,

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  • How do I use Spreadsheet::WriteExcel to create a chart from numeric log data?

    - by yaohung
    I used csv2xls.pl to convert a text log into .xls format, and then I create a chart as in the following: my $chart3 = $workbook->add_chart( type => 'line' , embedded => 1); # Configure the series. $chart3->add_series( categories => '=Sheet1!$B$2:$B$64', values => '=Sheet1!$C$2:$C$64', name => 'Test data series 1', ); # Add some labels. $chart3->set_title( name => 'Bridge Rate Analysis' ); $chart3->set_x_axis( name => 'Packet Size ' ); $chart3->set_y_axis( name => 'BVI Rate' ); # Insert the chart into the main worksheet. $worksheet->insert_chart( 'G2', $chart3 ); I can see the chart in the .xls file. However, all the data are in text format, not numeric, so the chart looks wrong. How do I convert text into number before applying this create-chart function? Also, how do I sort the .xls file before creating the chart?

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  • Choosing design method for ladder-like word game.

    - by owca
    I'm trying to build a simple application, with the finished program looking like this : I will also have to implement two different GUI layouts for this. Now I'm trying to figure out the best method to perform this task. My professor told me to introduce Element class with 4 states : - empty - invisible (used in GridLayout) - first letter - other letter I've thought about following solutions (by List I mean any sort of Collection) : 1. Element is a single letter, and each line is Element[]. Game class will be array of arrays Element[]. I guess that's the dumbest way, and the validation might be troublesome. 2. Like previously but Line is a List of Element. Game is an array of Lines. 3. Like previously but Game is a List of Lines. Which one should I choose ? Or maybe do you have better ideas ? What collection would be best if to use one ?

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  • What good open source programs exist for fuzzing popular image file types?

    - by JohnnySoftware
    I am looking for a free, open source, portable fuzzing tool for popular image file types that is written in either Java, Python, or Jython. Ideally, it would accept specifications for the fuzzable fields using some kind of declarative constraints. Non-procedural grammar for specifying constraints are greatly preferred. Otherwise, might as well write them all in Python or whatever. Just specifying ranges of valid values or expressions for them. Ideally, it would support some kind of generative programming to export the fuzzer into various programming languages to suit cases where more customization was required. If it supported a direct-manipulation GUI for controlling parameter values and ranges, that would be nice too. The file formats that should be supported are: GIF JPEG PNG So basically, it should be sort of a toolkit consisting of ready-to-run utility, a framework or library, and be capable of generating the fuzzed files directly as well as from programs it generates. It needs to be simple so that test images can be created quickly. It should have a batch capability for creating a series of images. Creating just one at a time would be too painful. I do not want a hacking tool, just a QA tool. Basically, I just want to address concerns that it is taking too long to get commonplace image rendering/parsing libraries stable and trustworthy.

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  • TextArea component is null on applicationComplete event

    - by Alan G.
    I have a weird issue (weird because it is specific to one component) with applicationComplete in a fairly simple application. All the UI components are declared in MXML. I can access them all in applicationComplete, but not a spark.components.TextArea component, named taStatus here; it is null in the handler. MXML looks sort of like this (there are lots of other components, but nothing special) <s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark" xmlns:mx="library://ns.adobe.com/flex/mx" minWidth="710" minHeight="640" applicationComplete="onApplicationComplete(event)" width="710" height="640"> <mx:TabNavigator left="15" right="15" top="15" bottom="340" paddingTop="0"> <s:NavigatorContent label="General" width="100%" height="100%"> <s:Label x="93" y="71" text="Label" id="lblTest"/> </s:NavigatorContent> <s:NavigatorContent label="Status" width="100%" height="100%"> <s:TextArea id="taStatus" width="100%" height="100%" text="Startup." editable="false"/> </s:NavigatorContent> </mx:TabNavigator> <fx:Script source="main.as" /> </s:Application> Here is the handler in main.as protected function onApplicationComplete(event: FlexEvent) : void { lblTest.text = 'abc789'; // OK taStatus.text = 'abc789'; // Fail } TypeError: Error #1009: Cannot access a property or method of a null object reference. So taStatus is null... What is so special about this TextArea?

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  • Getting the avg of the top 10 students from each school

    - by dave
    Hi all -- We have a school district with 38 elementary schools. The kids took a test. The averages for the schools are widely dispersed, but I want to compare the averages of JUST THE TOP 10 students from each school. Requirement: use temporary tables only. I have done this in a very work-intensive, error-prone sort of way as follows. (sch_code = e.g., 9043; -- schabbrev = e.g., "Carter"; -- totpct_stu = e.g., 61.3) DROP TEMPORARY TABLE IF EXISTS avg_top10 ; CREATE TEMPORARY TABLE avg_top10 ( sch_code VARCHAR(4), schabbrev VARCHAR(75), totpct_stu DECIMAL(5,1) ); INSERT INTO avg_top10 SELECT sch_code , schabbrev , totpct_stu FROM test_table WHERE sch_code IN ('5489') ORDER BY totpct_stu DESC LIMIT 10; -- I do that last query for EVERY school, so the total -- length of the code is well in excess of 300 lines. -- Then, finally... SELECT schabbrev, ROUND( AVG( totpct_stu ), 1 ) AS top10 FROM avg_top10 GROUP BY schabbrev ORDER BY top10 ; -- OUTPUT: ----------------------------------- schabbrev avg_top10 ---------- --------- Goulding 75.4 Garth 77.7 Sperhead 81.4 Oak_P 83.7 Spring 84.9 -- etc... Question: So this works, but isn't there a lot better way to do it? Thanks! PS -- Looks like homework, but this is, well...real.

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  • Trusted Folder/Drive Picker in the Browser

    - by kylepfritz
    I'd like to write a Folder/Drive picker the runs in the browser and allows a user to select files to upload to a webservice. The primary usage would be selecting folders or a whole CD and uploading them to the web with their directory structure in tact. I'm imagining something akin to Jumploader but which automatically enumerates external drives and CDs. I remember a version of Facebook's picture uploader that could do this sort of enumeration and was java-based but it has since been replaced by a much slicker plugin-based architecture. Because the application needs to run at very high trust, I think I'm limited to old-school java applets. Is there another alternative? I'm hesitant to start down the plugin route because of the necessity of writing one for both IE and Mozilla at a minimum. Are there good places to get started there? On the applet front, I built a clunky prototype to demonstrate that I can enumerate devices and list files. It runs fine in the applet viewer but I don't think I have the security settings configured correctly for it to run in the browser at full trust. Currently I don't get any drives back when I run it in the browser. Applet Prototype: public class Loader extends javax.swing.JApplet { ... private void EnumerateDrives(java.awt.event.ActionEvent evt) { File[] roots = File.listRoots(); StringBuilder b = new StringBuilder(); for (File root : roots) { b.append(root.getAbsolutePath() + ", "); } jLabel.setText(b.toString()); } } Embed Html: <p>Loader:</p> <script src="http://www.java.com/js/deployJava.js" type="text/javascript" ></script> <script> var attributes = {code:'org.exampl.Loader.Loader.class', archive:'Loader/dist/Loader.jar', width:600, height:400} ; var parameters = {}; deployJava.runApplet(attributes, parameters, '1.6');

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  • How to display a busy message over a wpf screen

    - by dave
    Hey, I have a WPF application based on Prism4. When performing slow operations, I want to show a busy screen. I will have a large number of screens, so I'm trying to build a single solution into the framework rather than adding the busy indicator to each screen. These long running operations run in a background thread. This allows the UI to be updated (good) but does not stop the user from using the UI (bad). What I'd like to do is overlay a control with a spinning dial sort of thing and have that control cover the entire screen (the old HTML trick with DIVs). When the app is busy, the control would display thus block any further interaction as well as showing the spinny thing. To set this up, I thought I could just have my app screen in a canvas along with the spinny thing (with a greater ZIndex) then just make the spinny thing visible as required. This, however, is getting hard. Canvases do not seem well set up for this and I think I might be barking up the wrong tree. I would appreciate any help. Thanks.

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  • How do you program a windows service in C# to start an application for a user?

    - by Swoop
    Is it possible to start a program so that it is available to a user with a windows service? I have been working with the Process.Start() in C#. I can get the service to kickoff some sort of process that appears in the Task Manager list under processes. However, the program nevers appears on the screen. By default, it runs under the user name "SYSTEM". I have adjusted the "Log On" option in the service manager to match the person logged into the computer, but this does not cause a window to appear either. I feel like I am either missing a simple setting, or need to take a different direction for this. Below is the code I have been working with to start up Firefox as a test app. private void startRunDap() { ProcessStartInfo startInfo = new ProcessStartInfo(); startInfo.FileName = "Firefox"; startInfo.WindowStyle = ProcessWindowStyle.Normal; startInfo.UseShellExecute = true; Process.Start(startInfo); //Process.Start("Firefox"); }

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  • Android Layout + Programming

    - by MD
    I'm trying to create a "scrollable" layout in Android. Even using developers.android.com, though, I feel a little bit lost at the moment. I'm somewhat new to Java, but not so much that I feel I should be having these issues--being new to Android is the bigger problem right now. The layout I'm trying to create should scroll in a sort of a "grid". I THINK what I'm looking for is the Gallery view, but I'm really lost as to how to implement it at the moment. I want it to "snap" to center the frame, like in the actual Gallery application. Essentially, if I had a photo gallery of 9 pictures, the idea is to scroll between them up/down AND side to side, in a 3x3 manner. Doesn't need to dynamically adjust, or anything like that, I just want a grid I can scroll through. I'm also not asking for anyone to give me explicit code for it--I'm trying to learn, more than anything. But pointing me in the right direction for helpful layout programming resources would be greatly appreciated, and confirming if it's a Gallery view I'm looking for would also be really helpful. Thanks in advance.

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  • building a gl3 app under cygwin

    - by user445264
    i've got a small opengl 3.2 app that i've been developing on linux using the standard gnu tools (gmake/gcc). the code seems pretty portable--i had no problems running it on osx until i started using gl3 features that the mac mini gl drivers don't seem to support. i've got a bootcamp partition with windows xp on the same mini, and i'd like to run my app there if possible. the windows drivers definitely support gl 3.2, but i'm having trouble linking. this seems like a really common issue, but i haven't found any answers online that address using opengl 1.2 under cygwin. i'm using glew-1.5.5 and linking like so: g++ -o glToy *.o -L/cygdrive/c/Program\ Files/glew-1.5.5/lib -lglew32 -lglut32 -lglu32 -lopengl32 but i get a whole lot of this sort of output: Program.o:/home/Jacob/glToy/Program.cpp:134: undefined reference to `__imp____glewUseProgram' Program.o:/home/Jacob/glToy/Program.cpp:235: undefined reference to `__imp____glewActiveTexture' Program.o:/home/Jacob/glToy/Program.cpp:73: undefined reference to `__imp____glewGetShaderiv' ... any ideas what i'm doing wrong? or perhaps this isn't a workable setup? other ideas for getting this going on the mac mini (2009 version)? thanks!

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  • Adding integer value to a list from XML file

    - by Pramodh
    I've an Xml file like <SampleFile> <Data> <Element Val="8" /> <Element Val="10" /> <Element Val="12" /> <Element Val="14" /> <Element Val="16" /> <Element Val="9" /> <Element Val="11" /> <Element Val="13" /> <Element Val="15" /> <Element Val="17" /> </Data> </SampleFile> i need to read the attribute value of" Val" and convert it to Int32 , then sort and then add to the list now i'm using like: List<Int32> lst = (XDocument.Load("\\Sample.xml").Descendants("Element").Select(l_Temp => l_Temp.Attribute("Val").Value.ToString()).Cast<Int32>().OrderBy(nTemp => nTemp)).ToList(); but its not working properly please give me a better solution

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  • Custom Controls Properties - C# , Forms - :(

    - by user353600
    Hi I m adding custom control to my flowlayoutpanel , its a sort of forex data , refresh every second , so on each timer tick , i m adding a control , changing controls button text , then adding it to flowlayout panel , i m doing it at each 100ms timer tick , it takeing tooo much CPU , here is my custom Control . public partial class UserControl1 : UserControl { public UserControl1() { InitializeComponent(); } private void UserControl1_Load(object sender, EventArgs e) { } public void displaydata(string name , string back3price , string back3 , string back2price , string back2 , string back1price , string back1 , string lay3price , string lay3 , string lay2price , string lay2 , string lay1price , string lay1 ) { lblrunnerName.Text = name.ToString(); btnback3.Text = back3.ToString() + "\n" + back3price.ToString(); btnback2.Text = back2.ToString() + "\n" + back2price.ToString(); btnback1.Text = back1.ToString() + "\n" + back1price.ToString(); btnlay1.Text = lay1.ToString() + "\n" + lay1price.ToString(); btnlay2.Text = lay2.ToString() + "\n" + lay2price.ToString(); btnlay3.Text = lay3.ToString() + "\n" + lay3price.ToString(); } and here is how i m adding control; private void timer1_Tick(object sender, EventArgs e) { localhost.marketData[] md; md = ser.getM1(); flowLayoutPanel1.Controls.Clear(); foreach (localhost.marketData item in md) { UserControl1 ur = new UserControl1(); ur.Name = item.runnerName + item.runnerID; ur.displaydata(item.runnerName, item.back3price, item.back3, item.back2price, item.back2, item.back1price, item.back1, item.lay3price, item.lay3, item.lay2price, item.lay2, item.lay1price, item.lay1); flowLayoutPanel1.SuspendLayout(); flowLayoutPanel1.Controls.Add(ur); flowLayoutPanel1.ResumeLayout(); } } now its happing on 10 times on each send , taking 60% of my Core2Duo cpu . is there any other way , i can just add contols first time , and then change the text of cutom controls buttons on runtime on each refresh or timer tick i m using c# .Net

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  • multiple clients - one server connection with sockets tcp/ip c# .net

    - by jagse
    Hello guys, I need to develop a client server system where I can have multiple clients communicating with one server at the same time. I want to communicate xml serialized objects and also need to send and receive other commands to invoke methods. Now, I am just starting with socket programming in C# and .Net and found that the asynchronous I/O is the way to go so that the methods dont block the execution of code. Also there are many examples of how to make a simple client server system. So I have a basic understanding of how that works. Anyway, what still is not clear to me is how I can set up a server which can manage connections to multiple clients? Can I just create a new socket per connection and then store those in some kind of list? Do I need some kind of multiplexing to achieve this? Do I have to listen at multiple ports? What`s the best way here? And the other thing is if I need to develop my own protocol to differentiate between what I am actually sending over the network -- xml serialized object or a command which might be just a string encoded in ascII or something. Or would I develop my own protocol just to send these commands? Any kind of help is apreciated! If someone knows a good book which covers this sort of stuff, let me know. Cheers I forgot to mention that some of my clients which are supposed to communicate with my server will be pda and I therefore use the compact framework... So this might bring in some restrictions...

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  • Can C++ do something like an ML case expression?

    - by Nathan Andrew Mullenax
    So, I've run into this sort of thing a few times in C++ where I'd really like to write something like case (a,b,c,d) of (true, true, _, _ ) => expr | (false, true, _, false) => expr | ... But in C++, I invariably end up with something like this: bool c11 = color1.count(e.first)>0; bool c21 = color2.count(e.first)>0; bool c12 = color1.count(e.second)>0; bool c22 = color2.count(e.second)>0; // no vertex in this edge is colored // requeue if( !(c11||c21||c12||c22) ) { edges.push(e); } // endpoints already same color // failure condition else if( (c11&&c12)||(c21&&c22) ) { results.push_back("NOT BICOLORABLE."); return true; } // nothing to do: nodes are already // colored and different from one another else if( (c11&&c22)||(c21&&c12) ) { } // first is c1, second is not set else if( c11 && !(c12||c22) ) { color2.insert( e.second ); } // first is c2, second is not set else if( c21 && !(c12||c22) ) { color1.insert( e.second ); } // first is not set, second is c1 else if( !(c11||c21) && c12 ) { color2.insert( e.first ); } // first is not set, second is c2 else if( !(c11||c21) && c22 ) { color1.insert( e.first ); } else { std::cout << "Something went wrong.\n"; } I'm wondering if there's any way to clean all of those if's and else's up, as it seems especially error prone. It would be even better if it were possible to get the compiler complain like SML does when a case expression (or statement in C++) isn't exhaustive. I realize this question is a bit vague. Maybe, in sum, how would one represent an exhaustive truth table with an arbitrary number of variables in C++ succinctly? Thanks in advance.

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  • MySql "comments" parameter as descriptor?

    - by Nick
    So, I'm trying to learn a lot at once, and this place is really helpful! I'm making a little running log website for myself and maybe a few other people, and I have it so that the user can add workouts for each day. With each workout, I have a variety of information the user can fill out for the workout, such as running distance, time, quality of run, course, etc... I store this in a MySql database as a table with fields titled "distance", "time", "runquality", etc... Now, these field titles don't match up with what I want displayed on the running log, so I was thinking of using the "Comments" attribute for a field to store its human-readable title--thus the field "runquality" would have "Quality of run" as its comment, and then I would pull the comment with a SQL query and display it instead of the field name. Is this a good theoretical/practical way of going about it? And what sort of SQL would I use to pull the comment for the field anyway? Secondly, suppose I want to add the ability for the user to create their own workout descriptors. So say a user wants to add a "temperature" descriptor for their workout. Should I create a script that adds fields to my workout table, or should I create a separate table listing only workout descriptors and somehow link the descriptor table with the "contents" table? I haven't learned any theory about database design or anything so any help is appreciated!

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  • C# Changing Objects within a List

    - by kwong22
    Hi, I'm having a little problem changing members of an object in a list using a found index. So this is the method I am currently working with: static void addToInventory(ref List<baseItem> myArray, baseItem item, float maxAmount, ref float currentAmount) { if (currentAmount + item.getWeight() <= maxAmount) { Console.WriteLine("item.Quantity = {0}", item.Quantity); if (myArray.Contains(item)) { Console.WriteLine("Item ({0}) already exists", item.Name); int id = myArray.IndexOf(item); myArray[id].Quantity += item.Quantity;//Change occurs in this line, item.Quantity becomes the same as myArray[id].Quantity } else { Console.WriteLine("Adding new item ({0})", item.Name); myArray.Add(item); } currentAmount += item.getWeight(); } else { Console.WriteLine("Inventory full"); } myArray.Sort(); } This method takes several parameters including the inventory/list. I check if the item fits in and if it does, I see if there is another item of the same name in the list, find the index, and add more of the item. However, the quantity of the item added suddenly becomes the same as the quantity of the item in the list. For some reason, this also changes the quantity of the item outside of the list. So therefore, instead of quantities adding up like this: 1, 2, 3, 4, they add up like this: 1, 2, 4, 8. I've just started to learn how to use lists so if there is anything I'm missing, don't hesitate to criticize. Thanks in advance.

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  • "no inclosing instance error " while getting top term frequencies for document from Lucene index

    - by Julia
    Hello ! I am trying to get the most occurring term frequencies for every particular document in Lucene index. I am trying to set the treshold of top occuring terms that I care about, maybe 20 However, I am getting the "no inclosing instance of type DisplayTermVectors is accessible" when calling Comparator... So to this function I pass vector of every document and max top terms i would like to know protected static Collection getTopTerms(TermFreqVector tfv, int maxTerms){ String[] terms = tfv.getTerms(); int[] tFreqs = tfv.getTermFrequencies(); List result = new ArrayList(terms.length); for (int i = 0; i < tFreqs.length; i++) { TermFrq tf = new TermFrq(terms[i], tFreqs[i]); result.add(tf); } Collections.sort(result, new FreqComparator()); if(maxTerms < result.size()){ result = result.subList(0, maxTerms); } return result; } /Class for objects to hold the term/freq pairs/ static class TermFrq{ private String term; private int freq; public TermFrq(String term,int freq){ this.term = term; this.freq = freq; } public String getTerm(){ return this.term; } public int getFreq(){ return this.freq; } } /*Comparator to compare the objects by the frequency*/ class FreqComparator implements Comparator{ public int compare(Object pair1, Object pair2){ int f1 = ((TermFrq)pair1).getFreq(); int f2 = ((TermFrq)pair2).getFreq(); if(f1 > f2) return 1; else if(f1 < f2) return -1; else return 0; } } Explanations and corrections i will very much appreciate, and also if someone else had experience with term frequency extraction and did it better way, I am opened to all suggestions! Please help!!!! Thanx!

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  • How do you tell that your unit tests are correct?

    - by Jacob Adams
    I've only done minor unit testing at various points in my career. Whenever I start diving into it again, it always troubles me how to prove that my tests are correct. How can I tell that there isn't a bug in my unit test? Usually I end up running the app, proving it works, then using the unit test as a sort of regression test. What is the recommended approach and/or what is the approach you take to this problem? Edit: I also realize that you could write small, granular unit tests that would be easy to understand. However, if you assume that small, granular code is flawless and bulletproof, you could just write small, granular programs and not need unit testing. Edit2: For the arguments "unit testing is for making sure your changes don't break anything" and "this will only happen if the test has the exact same flaw as the code", what if the test overfits? It's possible to pass both good and bad code with a bad test. My main question is what good is unit testing since if your tests can be flawed you can't really improve your confidence in your code, can't really prove your refactoring worked, and can't really prove that you met the specification?

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