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  • Convert enumeration to string

    - by emptyheaded
    I am trying to build a function that converts an item from an enum to its corresponding string. The enums I use are fairly long, so I didn't want to use a switch-case. I found a method using boost::unordered_map very convenient, but I don't know how to make a default return (when there is no item matching the enum). const boost::unordered_map<enum_type, const std::string> enumToString = boost::assign::map_list_of (data_1, "data_1") (data_2, "data_2"); I tried to create an additional function: std::string convert(enum_type entry) { if (enumToString.find(entry)) // not sure what test to place here, return enumToString.at(entry); //because the find method returns an iter else return "invalid_value"; } I even tried something exceedingly wrong: std::string convert(enum_type entry) { try{ return enumToString.at(entry); } catch(...){ return "invalid_value"; } } Result: evil "Debug" runtime error. Can somebody give me a suggestion on how to either 1) find an easier method to convert enum to a string with the same name as the enum item 2) find a way to use already built boost methods to get a default value from a hash map (best option) 3) find what to place in the test to use a function that returns either the pair of the key-value, or a different string if the key is not found in the map. Thank you very much.

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  • Named pipe stalls threads?

    - by entens
    I am attempting to push updates into a process via a named pipe, but in doing so my process loop now seams to stall on while ((line = sr.ReadLine()) != null). I'm a little mystified as to what might be wrong as this is my first foray into named pipes. void RefreshThread() { using (NamedPipeServerStream pipeStream = new NamedPipeServerStream("processPipe", PipeDirection.In)) { pipeStream.WaitForConnection(); using (StreamReader sr = new StreamReader(pipeStream)) { for (; ; ) { if (StopThread == true) { StopThread = false; return; // exit loop and terminate the thread } // push update for heartbeat int HeartbeatHandle = ItemDictionary["Info.Heartbeat"]; int HeartbeatValue = (int)Config.Items[HeartbeatHandle].Value; Config.Items[HeartbeatHandle].Value = ++HeartbeatValue; SetItemValue(HeartbeatHandle, HeartbeatValue, (short)0xC0, DateTime.Now); string line = null; while ((line = sr.ReadLine()) != null) { // line is in the format: item, value, timestamp string[] parts = line.Split(','); // push update and store value in item cache int handle = ItemDictionary[parts[0]]; object value = parts[1]; Config.Items[handle].Value = int.Parse(value); DateTime timestamp = DateTime.FromBinary(long.Parse(parts[2])); SetItemValue(handle, value, (short)0xC0, timestamp); } Thread.Sleep(500); } } } }

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  • jQuery Ajax call for buttons on a list

    - by lloydphillips
    I have a list of data that i have in a view from an asp.net mvc application. It's a list of stock and I have two images (a plus and a minus) on the end of each row which will allow me to increase or decrease stock quantity. It works fine at present with a call to the mvc action but since the list is long I want to use jQuery and AJAX to have the call go without a refresh. I want to do this with unobtrusive javascript so don't want onclick handlers on my images. Since I'm just starting out with jQuery I have no idea how I can iterate all the images and add the function. Here are the images with the form tags as they stand: <td> <% using (Html.BeginForm("Increase", "Stock", new { Id = item.StockId })) {%> <input type="image" src="/Content/Images/bullet_add.png" style="margin-left:20px;" /> <% } %> </td> <td><% using (Html.BeginForm("Decrease", "Stock", new { Id = item.StockId })) {%> <input type="image" src="/Content/Images/bullet_delete.png" style="margin-left:10px;" /><% } %> </td> Can anyone help me out a little? Many thanks. Lloyd

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  • Batch insert mode with hibernate and oracle: seems to be dropping back to slow mode silently

    - by Chris
    I'm trying to get a batch insert working with Hibernate into Oracle, according to what i've read here: http://docs.jboss.org/hibernate/core/3.3/reference/en/html/batch.html , but with my benchmarking it doesn't seem any faster than before. Can anyone suggest a way to prove whether hibernate is using batch mode or not? I hear that there are numerous reasons why it may silently drop into normal mode (eg associations and generated ids) so is there some way to find out why it has gone non-batch? My hibernate.cfg.xml contains this line which i believe is all i need to enable batch mode: <property name="jdbc.batch_size">50</property> My insert code looks like this: List<LogEntry> entries = ..a list of 100 LogEntry data classes... Session sess = sessionFactory.getCurrentSession(); for(LogEntry e : entries) { sess.save(e); } sess.flush(); sess.clear(); My 'logentry' class has no associations, the only interesting field is the id: @Entity @Table(name="log_entries") public class LogEntry { @Id @GeneratedValue public Long id; ..other fields - strings and ints... However, since it is oracle, i believe the @GeneratedValue will use the sequence generator. And i believe that only the 'identity' generator will stop bulk inserts. So if anyone can explain why it isn't running in batch mode, or how i can find out for sure if it is or isn't in batch mode, or find out why hibernate is silently dropping back to slow mode, i'd be most grateful. Thanks

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  • Is it legal to take sealed .NET framework class source and extend it?

    - by Giedrius
    To be short, I'm giving very specific example, but I'm interested in general situation. There is a FtpWebRequest class in .NET framework and it is missing some of new FTP operations, like MFCT. It is ok in a sense that this operation is still in draft mode, but it is not ok in a sense, that FtpWebRequest is sealed and there's no other way (at least I don't see it) to extend it with this new operation. Easiest way to do it would be take FtpWebRequest class source from .NET reference sources and extend it, in such way will be kept all the consistence in naming, implementation, etc. Question is how much legal it is? I won't sell this class as a product, I can publish my changes on web - nothing to hide here. If it is not legal, can I take this class source from mono and include in native .net project? Did you had similar case and how you solved it? Update: as long as extension method is offered, I'm pasting source from .NET framework which should show that extension methods are not the solution. So there's a property Method, where you can pass FTP command: public override string Method { get { return m_MethodInfo.Method; } set { if (String.IsNullOrEmpty(value)) { throw new ArgumentException(SR.GetString(SR.net_ftp_invalid_method_name), "value"); } if (InUse) { throw new InvalidOperationException(SR.GetString(SR.net_reqsubmitted)); } try { m_MethodInfo = FtpMethodInfo.GetMethodInfo(value); } catch (ArgumentException) { throw new ArgumentException(SR.GetString(SR.net_ftp_unsupported_method), "value"); } } } As you can see there FtpMethodInfo.GetMethodInfo(value) call in setter, which basically validates value against internal enum static array. Update 2: Checked mono implementation and it is not exact replica of native code + it does not implement some of the things.

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  • Deployment a web-site on IIS from another program

    - by slo2ols
    Hi, I developed a web-site on ASP.NET 3.5 SP1 platform. And additional I have 2 win services. My task is to build install package. I decided that Visual Studio install projects are not met my requirements. I design my own installer for this project, because I need to resolve many question and problem in install process. My problem: I need to deploy web-site into IIS, but I don't know how to do it easy. I found Microsoft tool as Web Deployment Tool, but I didn't find any documentation. And must I include this tool into my installer for deployment at destination customer? Another side I found SDC Tasks Library and it looks like a solution for me. But I saw many topics where people had problems and because the project was dead anybody couldn't help them. I know it is a long story... My question: how can I deploy the web-site from another program (I know that IIS versions have some differences and it is another headache), set a virtual directory, application pool (very important), a type of authentification and so forth ??? Thanks.

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  • Copy only files that are newer

    - by ErocM
    I am currently using this code: if (!Directory.Exists(command2)) Directory.CreateDirectory(command2); if (Directory.Exists(vmdaydir)) Directory.Delete(vmdaydir,true); if (!Directory.Exists(vmdaydir)) Directory.CreateDirectory(vmdaydir); var dir = Path.GetDirectoryName(args[0]); sb.AppendLine("Backing Up VM: " + DateTime.Now.ToString(CultureInfo.InvariantCulture)); Microsoft.VisualBasic.FileIO.FileSystem.CopyDirectory(dir, vmdaydir); sb.AppendLine("VM Backed Up: " + DateTime.Now.ToString(CultureInfo.InvariantCulture)); As you can see, I am deleting the directory, then I am copying the folder back. This is taking way to long since the directory is ~80gb in size. I realized that I do not need to copy all the files, only the ones that have changed. How would I copy the files from one folder to another but only copying the files that are newer? Anyone have any suggestions? ==== edit ==== I assume I can just do a file compare of each file and then copy it to the new directory, iterating through each folder/file? Is there a simpler way to do this?

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  • Fitting Text into an Image

    - by Abs
    Hello all, I have a function which takes in a font (ttf or otf file) and generates an image of text in different fonts. The problem I have is trying to work out how I can make the text fit in the image regardless of the font-size, type of font, and amount of text. I have tried to make the image rectangle variable so that it contains the text of different fonts without cutting a bit of the text since the image is not long or wide enough. Here is the function that I currently have, I have tried using the number of characters to determine the width of the image, but in some cases for some fonts and sizes, it still gets cut off. function generate_image($save_path, $text, $font_path){ $length = strlen($text) * 15; // Create the image $im = imagecreatetruecolor($length, 40); $white = imagecolorallocate($im, 255, 255, 255); $grey = imagecolorallocate($im, 128, 128, 128); $black = imagecolorallocate($im, 0, 0, 0); imagefilledrectangle($im, 0, 0, $length, 40, $white); $font = $font_path; imagettftext($im, 30, 0, 0, 25, $black, $font, $text); if(imagepng($im, $save_path)){ $status = true; }else{ $status = false; } imagedestroy($im); return $status; } Thank you all for any help

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  • passing data from an activity to an listactivity or listview

    - by wicked14
    need help on passing data from an activity to an listactivity or listview for an android app. im having problems on passing data to a listview. what the app do is from addact class the user can input things to do and in the viewact class this will display the activies add by the user in listview public class addact extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.newact); Button btn1 = (Button)findViewById(R.id.btnsave); final EditText et1 = (EditText)findViewById(R.id.etactivity); btn1.setOnClickListener(new OnClickListener() { @Override public void onClick(View arg0) { Intent it = new Intent(addact.this, viewact.class); it.putExtra("thekey", et1.getText().toString()); startActivity(it); } }); } } public class viewact extends ListActivity { String addToDo =getIntent().getExtras().getString("thekey"); String[] toDoAct = new String[] {addToDo }; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.viewact); setListAdapter(new ArrayAdapter<String>(this, R.layout.viewact,toDoAct)); ListView listView = getListView(); listView.setTextFilterEnabled(true); listView.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> parent, View view, int position, long id) { for (int i=0; i < 2; i++) { Toast.makeText(getApplicationContext(), ((TextView) view).getText(), Toast.LENGTH_LONG).show(); } } }); } }

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  • Suffix if statement

    - by Aardschok
    I was looking for a way to add a suffix to jointchain in Maya. The jointchain has specific naming so I create a list with the names they need to be. The first chain has "_1" as suffix, result: R_Clavicle_1|R_UpperArm_1|R_UnderArm_1|R_Wrist_1 When I create the second this is the result: R_Clavicle_2|R_UpperArm_1|R_UnderArm_1|R_Wrist_1 The code: DRClavPos = cmds.xform ('DRClavicle', q=True, ws=True, t=True) DRUpArmPos = cmds.xform ('DRUpperArm', q=True, ws=True, t=True) DRUnArmPos = cmds.xform ('DRUnderArm', q=True, ws=True, t=True) DRWristPos = cmds.xform ('DRWrist', q=True, ws=True, t=True), cmds.xform('DRWrist', q=True, os=True, ro=True) suffix = 1 jntsA = cmds.ls(type="joint", long=True) while True: jntname = ["R_Clavicle_"+str(suffix),"R_UpperArm_"+str(suffix),"R_UnderArm_"+str(suffix),"R_Wrist_"+str(suffix)] if jntname not in jntsA: cmds.select (d=True) cmds.joint ( p=(DRClavPos)) cmds.joint ( p=(DRUpArmPos)) cmds.joint ( 'joint1', e=True, zso=True, oj='xyz', radius=0.5, n=jntname[0]) cmds.joint ( p=(DRUnArmPos)) cmds.joint ( 'joint2', e=True, zso=True, oj='xyz', radius=0.5, n=jntname[1]) cmds.joint ( p=(DRWristPos[0])) cmds.joint ( 'joint3', e=True, zso=True, oj='xyz', radius=0.5, n=jntname[2]) cmds.rename ('joint4', jntname[3]) cmds.select ( cl=True) break else: suffix + 1 I tried adding +1 in jntname which resulted in a good second chain but the third chain had "_2" after R_Clavicle_3 The code, in my eyes should work. Can anybody point me in the correct direction :)

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  • Domain validates but won't save

    - by marko
    I have the following setup. Class, say, Car that has a CarPart (belongsTo=[car:Car]). When I'm creating a Car I also want to create som default CarParts, so I do def car = new Car(bla bla bla) def part = new CarPart(car:car) Now, when I do car.validate() or part.validate() it seems fine. But when I do if(car.save && part.save() I get this exception: 2012-03-24 14:02:21,943 [http-8080-4] ERROR util.JDBCExceptionReporter - Batch entry 0 insert into car_part (version, car_id, id) values ('0', '297', '298') was aborted. Call getNextException to see the cause. 2012-03-24 14:02:21,943 [http-8080-4] ERROR util.JDBCExceptionReporter - ERROR: value too long for type character varying(6) 2012-03-24 14:02:21,943 [http-8080-4] ERROR events.PatchedDefaultFlushEventListener - Could not synchronize database state with session org.hibernate.exception.DataException: Could not execute JDBC batch update Stacktrace follows: java.sql.BatchUpdateException: Batch entry 0 insert into car_part (version, deal_id, id) values ('0', '297', '298') was aborted. Call getNextException to see the cause. at org.postgresql.jdbc2.AbstractJdbc2Statement$BatchResultHandler.handleError(AbstractJdbc2Statement.java:2621) at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1837) at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:407) at org.postgresql.jdbc2.AbstractJdbc2Statement.executeBatch(AbstractJdbc2Statement.java:2754) at $Proxy20.flush(Unknown Source) at ristretto.DealController$_closure5.doCall(DealController.groovy:109) at ristretto.DealController$_closure5.doCall(DealController.groovy) at java.lang.Thread.run(Thread.java:722) Any ideas?

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  • Changing the Hibernate 3 settings

    - by Bogdanel
    I use Hibernate3 and Hibernate Tools 3.2.4 to generate hbm.xml and java files and I want to use List instead of HashSet(...). I've tried to modify the hbm.xml files, putting list instead of set. Is there any way to specify to hibernate tools that I want to generate automatically a list not a HashSet? This is an exemple: Java class public class Test implements java.io.Serializable { private Long testId; private Course course; private String testName; private Set<Question> questions = new HashSet<Question>( 0 ); } Test.hbm.xml: <set name="questions" inverse="true" lazy="true" table="questions" fetch="select"> <key> <column name="test_id" not-null="true" /> </key> <one-to-many class="com.app.objects.Question" /> ... </set> I thought that I could find a clue in the "reveng.xml" file, but I failed.

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  • please check my MYSQL query & give me advice?

    - by Suba
    select s.s_nric as NRIC,s.s_name as NAME,s.s_psle_eng as PSLE_ENG,s.s_psle_math as PSLE_MATHS,s.s_psle_aggr as PSLE_AGGR, (SELECT re.re_mark FROM si_results re WHERE re.re_code like 'FEEN%' AND re.re_year='2008' AND re.re_semester='2' AND re.re_nric=s.s_nric ) as English_2008, (SELECT re.re_mark FROM si_results re WHERE re.re_code like 'FEMA%' AND re.re_year='2008' AND re.re_semester='2' AND re.re_nric=s.s_nric ) Maths_2008, (SELECT re.re_mark FROM si_results re WHERE re.re_code like 'FEEN%' AND re.re_year='2009' AND re.re_semester='2' AND re.re_nric=s.s_nric ) as English_2009, (SELECT re.re_mark FROM si_results re WHERE re.re_code like 'FEMA%' AND re.re_year='2009' AND re.re_semester='2' AND re.re_nric=s.s_nric ) Maths_2009 ,isc.isc_g_gpa as ISC_GPA from si_student_data as s LEFT JOIN si_isc_gpa as isc ON isc.isc_g_nric=s.s_nric where 1=1 AND s.s_admission_year='2008' GROUP BY s.s_nric ORDER BY s.s_gender,s.s_name asc This is my query. please check my sub query this is my sub query (SELECT re.re_mark FROM si_results re WHERE re.re_code like 'FEEN%' AND re.re_year='2008' AND re.re_semester='2' AND re.re_nric=s.s_nric ) as English_2008, (SELECT re.re_mark FROM si_results re WHERE re.re_code like 'FEMA%' AND re.re_year='2008' AND re.re_semester='2' AND re.re_nric=s.s_nric ) Maths_2008, (SELECT re.re_mark FROM si_results re WHERE re.re_code like 'FEEN%' AND re.re_year='2009' AND re.re_semester='2' AND re.re_nric=s.s_nric ) as English_2009, (SELECT re.re_mark FROM si_results re WHERE re.re_code like 'FEMA%' AND re.re_year='2009' AND re.re_semester='2' AND re.re_nric=s.s_nric ) Maths_2009 When I execute my query, server take long time to execute. So how to make simple? please advice me. Thanks.

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  • Programmatically change the icon of the executable

    - by Dennis Delimarsky
    I am developing an application called WeatherBar. Its main functionality is based on its interaction with the Windows 7 taskbar — it changes the icon depending on the weather conditions in a specific location. The icons I am using in the application are all stored in a compiled native resource file (.res) — I am using it instead of the embedded resource manifest for icons only. By default, I modify the Icon property of the main form to change the icons accordingly and it works fine, as long as the icon is not pinned to the taskbar. When it gets pinned, the icon in the taskbar automatically switches to the default one for the executable (with index 0 in the resource file). After doing a little bit of research, I figured that a way to change the icon would be changing the shortcut icon (as all pinned applications are actually shortcuts stored in the user folder). But it didn't work. I assume that I need to change the icon for the executable, and therefore use UpdateResource, but I am not entirely sure about this. My executable is not digitally signed, so it shouldn't be an issue modifying it. What would be the way to solve this issue?

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  • Strange data swapping error occurs when I attempt to update rows in my table from another table in m

    - by Wesley
    So I have a table of data that is 10,000 lines long. Several of the columns in the table simply describe information about one of the columns, meaning, that only one column has the content, and the rest of the columns describe the location of the content (its for a book). Right now, only 6,000 of the 10,000 rows' content column is filled with its content. Rows 6-10,000's content column simply says null. I have another table in the db that has the content for rows 6,000-10,000, with the correct corresponding primary key which would (seemingly) make it easy to update the 10,000 row table. I have been trying an update query such as the following: UPDATE table(10,000) SET content_column = (SELECT content FROM table(6,000-10,000) WHERE table(10,000).id = table(6-10,000.id) Which kind of works, the only problem is that it pulls in the data from the second table just fine, but it replaces the existing content column with null. So rows 1-6,000's content column become null, and rows 6-10,000's content column have the correct values...Pretty strange I thought anyway. Does anybody have any thoughts about where I am going wrong? If you could show me a better sql query, I would appreciate it! Thanks

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  • PHP Object Access Syntax Question with the $

    - by ImperialLion
    I've been having trouble searching for this answer because I am not quite sure how to phrase it. I am new to PHP and still getting my feet on the ground. I was writing a page with a class in it that had the property name. When I originally wrote the page there was no class so I just had a variable called $name. When I went to encapsulate it in a class I accidental changed it to be $myClass->$name. It tool me a while to realize that the syntax I needed was $myClass->name. The reason it took so long was the error I kept getting was "Attempt to access a null property" or something along those lines. The error lead me to believe it was a data population error. My question is does $myClass->$name have a valid meaning? In other words is there a time you would use this and a reason why it doesn't create a syntax error? If so what is the semantic meaning of that code? When would I use it if it is valid? If its not valid, is there a reason that it doesn't create a syntax error?

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  • Which is the best license for my Open Source project?

    - by coderex
    I am a web developer, and I don't have enough knowledge about software licenses. I wish to publish some of my works, and I need to select licenses for them. My software product is free of cost. But I have some restrictions on the distribution/modification of the code. It's free of cost (but donations are acceptable ;-)). The source code is freely available. You can use, customize or edit/remove code (as long as the basic nature of the software is not changed). You don't have any permission to change the product name. There are some libraries and classes which are in a folder caller "myname". You don't have the permission to rename "myname". You can contribute any additions or modifications to my project, to the original source repository (the contributors name/email/site link will be listed on the credit file). You can't remove the original author's name from the license. You can put the license file or license code anywhere in the project file or folder. You can redistribute this code as free or commercial software. :) Do you think all these restrictions are valid? Given these restrictions, which license should I use? Edit 1:- My main intention is to make the product more popular with free source code while ensuring the original author is not ignored. The product is open. Edit 2:- Thank you all, the above points are because of my lack of knowledge of license terms. You can help me to correct or remove some of the above points. What I'm basically looking for is in my Edit 1.

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  • Linux apache developing configuration

    - by Jeffrey Vandenborne
    Recenly reinstalled my system, and came to a point where I need apache and php. I've been searching a long time, but I can't figure out how to configure apache the best way for a developer computer. The plan is simple, I want to install apache 2 + mysql server so I can develop some php website. I don't want to install lamp though, just the apache2, php5 and mysql. The problem that I've been looking an answer for is the permissions on the /var/www/ folder. I've tried making it my folder using the chown command, followed by a chmod -R 755 /var/www. Most things work then, but fwrite for example won't work, because I need to give write permissions to everyone, unless I change my global umask to 000 I'm not sure what I can do. In short: I want to install apache2, php5, mysql-server without using lamp, but configured in a way so I can open up netbeans, start a project with root in /var/www/, and run every single function without permission faults. Does anyone have experiences or workarounds to this? Extra: OS: Ubuntu 10.04 ARCH: x86_64

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  • Computation overhead in C# - Using getters/setters vs. modifying arrays directly and casting speeds

    - by Jeffrey Kern
    I was going to write a long-winded post, but I'll boil it down here: I'm trying to emulate the graphical old-school style of the NES via XNA. However, my FPS is SLOW, trying to modify 65K pixels per frame. If I just loop through all 65K pixels and set them to some arbitrary color, I get 64FPS. The code I made to look-up what colors should be placed where, I get 1FPS. I think it is because of my object-orented code. Right now, I have things divided into about six classes, with getters/setters. I'm guessing that I'm at least calling 360K getters per frame, which I think is a lot of overhead. Each class contains either/and-or 1D or 2D arrays containing custom enumerations, int, Color, or Vector2D, bytes. What if I combined all of the classes into just one, and accessed the contents of each array directly? The code would look a mess, and ditch the concepts of object-oriented coding, but the speed might be much faster. I'm also not concerned about access violations, as any attempts to get/set the data in the arrays will done in blocks. E.g., all writing to arrays will take place before any data is accessed from them. As for casting, I stated that I'm using custom enumerations, int, Color, and Vector2D, bytes. Which data types are fastest to use and access in the .net Framework, XNA, XBox, C#? I think that constant casting might be a cause of slowdown here. Also, instead of using math to figure out which indexes data should be placed in, I've used precomputed lookup tables so I don't have to use constant multiplication, addition, subtraction, division per frame. :)

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  • Slow query. Wrong database structure?

    - by Tin
    I have a database with table that contains tasks. Tasks have a lifecycle. The status of the task's lifecycle can change. These state transitions are stored in a separate table tasktransitions. Now I wrote a query to find all open/reopened tasks and recently changed tasks but I already see with a rather small number of tasks (<1000) that execution time has becoming very long (0.5s). Tasks +-------------+---------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------------+---------+------+-----+---------+----------------+ | taskid | int(11) | NO | PRI | NULL | auto_increment | | description | text | NO | | NULL | | +-------------+---------+------+-----+---------+----------------+ Tasktransitions +------------------+-----------+------+-----+-------------------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------------+-----------+------+-----+-------------------+----------------+ | tasktransitionid | int(11) | NO | PRI | NULL | auto_increment | | taskid | int(11) | NO | MUL | NULL | | | status | int(11) | NO | MUL | NULL | | | description | text | NO | | NULL | | | userid | int(11) | NO | | NULL | | | transitiondate | timestamp | NO | | CURRENT_TIMESTAMP | | +------------------+-----------+------+-----+-------------------+----------------+ Query SELECT tasks.taskid,tasks.description,tasklaststatus.status FROM tasks LEFT OUTER JOIN ( SELECT tasktransitions.taskid,tasktransitions.transitiondate,tasktransitions.status FROM tasktransitions INNER JOIN ( SELECT taskid,MAX(transitiondate) AS lasttransitiondate FROM tasktransitions GROUP BY taskid ) AS tasklasttransition ON tasklasttransition.lasttransitiondate=tasktransitions.transitiondate AND tasklasttransition.taskid=tasktransitions.taskid ) AS tasklaststatus ON tasklaststatus.taskid=tasks.taskid WHERE tasklaststatus.status IS NULL OR tasklaststatus.status=0 or tasklaststatus.transitiondate>'2013-09-01'; I'm wondering if the database structure is best choice performance wise. Could adding indexes help? I already tried to add some but I don't see great improvements. +-----------------+------------+----------------+--------------+------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | +-----------------+------------+----------------+--------------+------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ | tasktransitions | 0 | PRIMARY | 1 | tasktransitionid | A | 896 | NULL | NULL | | BTREE | | | | tasktransitions | 1 | taskid_date_ix | 1 | taskid | A | 896 | NULL | NULL | | BTREE | | | | tasktransitions | 1 | taskid_date_ix | 2 | transitiondate | A | 896 | NULL | NULL | | BTREE | | | | tasktransitions | 1 | status_ix | 1 | status | A | 3 | NULL | NULL | | BTREE | | | +-----------------+------------+----------------+--------------+------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+ Any other suggestions?

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  • C# Convert string to nullable type (int, double, etc...)

    - by Nathan Koop
    I am attempting to do some data conversion. Unfortunately, much of the data is in strings, where it should be int's or double, etc... So what I've got is something like: double? amount = Convert.ToDouble(strAmount); The problem with this approach is if strAmount is empty, if it's empty I want it to amount to be null, so when I add it into the database the column will be null. So I ended up writing this: double? amount = null; if(strAmount.Trim().Length>0) { amount = Convert.ToDouble(strAmount); } Now this works fine, but I now have five lines of code instead of one. This makes things a little more difficult to read, especially when I have a large amount of columns to convert. I thought I'd use an extension to the string class and generic's to pass in the type, this is because it could be a double, or an int, or a long. So I tried this: public static class GenericExtension { public static Nullable<T> ConvertToNullable<T>(this string s, T type) where T: struct { if (s.Trim().Length > 0) { return (Nullable<T>)s; } return null; } } But I get the error: Cannot convert type 'string' to 'T?' Is there a way around this? I am not very familiar with creating methods using generics.

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  • How can I make hundreds of simultaneously running processes communicate with a database through one

    - by Olfan
    Long speech short: How can I make hundreds of simultaneously running processes communicate with a database through one or few permanent sessions? The whole story: I once built a number crunching engine that handles vast amounts of large data files by forking off one child after another giving each a small number of files to work on. File locking, progress monitoring and result propagation happen in an Oracle database which all (sub-)processes access at various times using an application-specific module which encapsulates DBI. This worked well at first, but now with higher volumes of input data, the number of database sessions (one per child, and they can be very short-lived) constantly being opened and closed is becoming an issue. I now want to centralise database access so that there are only one or few fixed database sessions which handle all database access for all the (sub-)processes. The presence of the database abstraction module should make the changes easy because the function calls in the worker instances can stay the same. My problem is that I cannot think of a suitable way to enhance said module in order to establish communication between all the processes and the database connector(s). I thought of message queueing, but couldn't come up with a way of connecting a large herd of requestors with one or few database connectors in a way so that bidirectional communication is possible (for collecting the query result). An asynchronous approach could help here in that all requests are written to the same queue and the database connector servicing the request will "call back" to submit the result. But my mind fails me in generating an image clear enough so that I can paint into code. Threading instead of forking might have given me an easier start, but this would now require massive changes to the code base that I'm not prepared to do to a live system. The more I think of it, the more the base idea looks like a pre-forked web server to me only that it doesn't serve web pages but database queries. Any ideas on what to dig into, and where? Sample (pseudo) code to inspire me, links to possibly related articles, ready solutions on CPAN maybe?

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  • Strange results while measuring delta time on Linux

    - by pachanga
    Folks, could you please explain why I'm getting very strange results from time to time using the the following code: #include <unistd.h> #include <sys/time.h> #include <time.h> #include <stdio.h> int main() { struct timeval start, end; long mtime, seconds, useconds; while(1) { gettimeofday(&start, NULL); usleep(2000); gettimeofday(&end, NULL); seconds = end.tv_sec - start.tv_sec; useconds = end.tv_usec - start.tv_usec; mtime = ((seconds) * 1000 + useconds/1000.0) + 0.5; if(mtime > 10) printf("WTF: %ld\n", mtime); } return 0; } (You can compile and run it with: gcc test.c -o out -lrt && ./out) What I'm experiencing is sporadic big values of mtime variable almost every second or even more often, e.g: $ gcc test.c -o out -lrt && ./out WTF: 14 WTF: 11 WTF: 11 WTF: 11 WTF: 14 WTF: 13 WTF: 13 WTF: 11 WTF: 16 How can this be possible? Is it OS to blame? Does it do too much context switching? But my box is idle( load average: 0.02, 0.02, 0.3). Here is my Linux kernel version: $ uname -a Linux kurluka 2.6.31-21-generic #59-Ubuntu SMP Wed Mar 24 07:28:56 UTC 2010 i686 GNU/Linux

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  • 3D and AI basics. The foundation before the coding.

    - by Allan
    Hi, everyone. (If you have the time and patience:) I've recently made the decision to study programming seriously and I'm about to order TAOCP and Concrete Mathematics to begin my studies (please don't get caught up on this). I'm very much interested in learning and understanding how 3D works but I'm aware that if I plan to do it right there's still a long walk before I get to actually play with 3D coding. Now to the question.. (tl;dr) Excluding programming itself, what disciplines do I have to be familiar with to code 3D? What kinds of mathematics? Physics? What else? What books do you recommend on such subjects? Now read it all again but replacing "3D" with "AI". Please don't recommend computer-specific books. The question is about the foundation to be learned before using the machine. Also, if possible, please keep the list brief; I plan to order one book on each subject but no more than that for now. Excuse me for any English mistakes, it's not my first language. Thank you.

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  • Statistical analysis on large data set to be published on the web

    - by dassouki
    I have a non-computer related data logger, that collects data from the field. This data is stored as text files, and I manually lump the files together and organize them. The current format is through a csv file per year per logger. Each file is around 4,000,000 lines x 7 loggers x 5 years = a lot of data. some of the data is organized as bins item_type, item_class, item_dimension_class, and other data is more unique, such as item_weight, item_color, date_collected, and so on ... Currently, I do statistical analysis on the data using a python/numpy/matplotlib program I wrote. It works fine, but the problem is, I'm the only one who can use it, since it and the data live on my computer. I'd like to publish the data on the web using a postgres db; however, I need to find or implement a statistical tool that'll take a large postgres table, and return statistical results within an adequate time frame. I'm not familiar with python for the web; however, I'm proficient with PHP on the web side, and python on the offline side. users should be allowed to create their own histograms, data analysis. For example, a user can search for all items that are blue shipped between week x and week y, while another user can search for sort the weight distribution of all items by hour for all year long. I was thinking of creating and indexing my own statistical tools, or automate the process somehow to emulate most queries. This seemed inefficient. I'm looking forward to hearing your ideas Thanks

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