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• Are local variables in Fortran 77 static or stack dynamic?

  - by mm2887

  For my programming languages class one hw problem asks: Are local variables in FORTRAN static or stack dynamic? Are local variables that are INITIALIZED to a default value static or stack dynamic? Show me some code with an explanation to back up your answer. Hint: The easiest way to check this is to have your program test the history sensitivity of a subprogram. Look at what happens when you initialize the local variable to a value and when you don’t. You may need to call more than one subprogram to lock in your answer with confidence. I wrote a few subroutines: - create a variable - print the variable - initialize the variable to a value - print the variable again Each successive call to the subroutine prints out the same random value for the variable when it is uninitialized and then it prints out the initialized value. What is this random value when the variable is uninitialized? Does this mean Fortran uses the same memory location for each call to the subroutine or it dynamically creates space and initializes the variable randomly? My second subroutine also creates a variable, but then calls the first subroutine. The result is the same except the random number printed of the uninitialized variable is different. I am very confused. Please help! Thank you so much.

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• Fast JSON serialization (and comparison with Pickle) for cluster computing in Python?

  - by user248237

  I have a set of data points, each described by a dictionary. The processing of each data point is independent and I submit each one as a separate job to a cluster. Each data point has a unique name, and my cluster submission wrapper simply calls a script that takes a data point's name and a file describing all the data points. That script then accesses the data point from the file and performs the computation. Since each job has to load the set of all points only to retrieve the point to be run, I wanted to optimize this step by serializing the file describing the set of points into an easily retrievable format. I tried using JSONpickle, using the following method, to serialize a dictionary describing all the data points to file: def json_serialize(obj, filename, use_jsonpickle=True): f = open(filename, 'w') if use_jsonpickle: import jsonpickle json_obj = jsonpickle.encode(obj) f.write(json_obj) else: simplejson.dump(obj, f, indent=1) f.close() The dictionary contains very simple objects (lists, strings, floats, etc.) and has a total of 54,000 keys. The json file is ~20 Megabytes in size. It takes ~20 seconds to load this file into memory, which seems very slow to me. I switched to using pickle with the same exact object, and found that it generates a file that's about 7.8 megabytes in size, and can be loaded in ~1-2 seconds. This is a significant improvement, but it still seems like loading of a small object (less than 100,000 entries) should be faster. Aside from that, pickle is not human readable, which was the big advantage of JSON for me. Is there a way to use JSON to get similar or better speed ups? If not, do you have other ideas on structuring this? (Is the right solution to simply "slice" the file describing each event into a separate file and pass that on to the script that runs a data point in a cluster job? It seems like that could lead to a proliferation of files). thanks.

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• How to best show progress info when using ADO.NET?

  - by Yadyn

  I want to show the user detailed progress information when performing potentially lengthy database operations. Specifically, when inserting/updating data that may be on the order of hundreds of KB or MB. Currently, I'm using in-memory DataTables and DataRows which are then synced with the database via TableAdapter.Update calls. This works fine and dandy, but the single call leaves little opportunity to glean any kind of progress info to show to the user. I have no idea how much data is passing through the network to the remote DB or its progress. Basically, all I know is when Update returns and it is assumed complete (barring any errors or exceptions). But this means all I can show is 0% and then a pause and then 100%. I can count the number of rows, even going so far to cound how many are actually Modified or Added, and I could even maybe calculate per DataRow its estimated size based on the datatype of each column, using sizeof for value types like int and checking length for things like strings or byte arrays. With that, I could probably determine, before updating, an estimated total transfer size, but I'm still stuck without any progress info once Update is called on the TableAdapter. Am I stuck just using an indeterminate progress bar or mouse waiting cursor? Would I need to radically change our data access layer to be able to hook into this kind of information? Even if I can't get it down to the precise KB transferred (like a web browser file download progress bar), could I at least know when each DataRow/DataTable finishes or something? How do you best show this kind of progress info using ADO.NET?

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• How to invalidate cache when benchmarking?

  - by Michael Buen

  I have this code, that when swapping the order of UsingAs and UsingCast, their performance also swaps. using System; using System.Diagnostics; using System.Linq; using System.IO; class Test { const int Size = 30000000; static void Main() { object[] values = new MemoryStream[Size]; UsingAs(values); UsingCast(values); Console.ReadLine(); } static void UsingCast(object[] values) { Stopwatch sw = Stopwatch.StartNew(); int sum = 0; foreach (object o in values) { if (o is MemoryStream) { var m = (MemoryStream)o; sum += (int)m.Length; } } sw.Stop(); Console.WriteLine("Cast: {0} : {1}", sum, (long)sw.ElapsedMilliseconds); } static void UsingAs(object[] values) { Stopwatch sw = Stopwatch.StartNew(); int sum = 0; foreach (object o in values) { if (o is MemoryStream) { var m = o as MemoryStream; sum += (int)m.Length; } } sw.Stop(); Console.WriteLine("As: {0} : {1}", sum, (long)sw.ElapsedMilliseconds); } } Outputs: As: 0 : 322 Cast: 0 : 281 When doing this... UsingCast(values); UsingAs(values); ...Results to this: Cast: 0 : 322 As: 0 : 281 When doing just this... UsingAs(values); ...Results to this: As: 0 : 322 When doing just this: UsingCast(values); ...Results to this: Cast: 0 : 322 Aside from running them independently, how to invalidate the cache so the second code being benchmarked won't receive the cached memory of first code? Benchmarking aside, just loved the fact that modern processors do this caching magic :-)

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• Niewbie OutOfMemory problem

  - by Nick

  So I am trying to create a producer/consumer type scala app. The LoopControl just sends a message to the MessageReceiver continoually. The MessageReceiver then delegates work to the MessageCreatorActor (whose work is to check a map for an object, and if not found create one and start it up). Each MessageActor created by this MessageCreatorActor is associated with an Id. Eventually this is where I want to do business logic. But I run out of memory after 15 minutes. Any help is appreciated import scala.actors.Actor import java.util.HashMap; import scala.actors.Actor._ case object LoopControl case object MessageReceiver case object MessageActor case object MessageActorCreator class MessageReceiver(msg: String) extends Actor { var messageActorMap = new HashMap[String, MessageActor] val messageCreatorActor = new MessageActorCreator(null, null) def act() { messageCreatorActor.start loop { react { case MessageActor(messageId) = if (msg.length() 0) { var messageActor = messageActorMap.get(messageId); if(messageActor == null) { messageCreatorActor ! MessageActorCreator(messageId, messageActorMap) }else { messageActor ! MessageActor } } } } } } case class MessageActorCreator(msg:String, messageActorMap: HashMap[String, MessageActor]) extends Actor { def act() { loop { react { case MessageActorCreator(messageId, messageActorMap) = if(messageId != null ) { var messageActor = new MessageActor(messageId); messageActorMap.put(messageId, messageActor) println(messageActorMap) messageActor.start messageActor ! MessageActor } } } } } class LoopControl(messageReceiver:MessageReceiver) extends Actor { var count : Int = 0; def act() { while (true) { messageReceiver ! MessageActor ("00-122-0X95-FEC0" + count) //Thread.sleep(100) count = count +1; if(count 5) { count = 0; } } } } case class MessageActor(msg: String) extends Actor { def act() { loop { react { case MessageActor = println() println("MessageActor: Got something- " + msg) } } } } object messages extends Application { val messageReceiver = new MessageReceiver("bootstrap") val loopControl = new LoopControl(messageReceiver) messageReceiver.start loopControl.start }

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• How to get the "real" colors when exporting a GDI drawing to bmp

  - by Rodrigo

  Hi guys I'm developing a ASP.Net web handler that returns images making a in-memory System.Windows.Forms.Control and then exports the rendered control as a bitmap compressed to PNG, using the method DrawToBitmap(). The classes are fully working by now, except for a problem with the color assignment. By example, this is a Gauge generated by the web handler. The colors assigned to the inner parts of the gauge are red (#FF0000), yellow (#FFFF00) and green (#00FF00) but I only get a dully version of each color (#CB100F for red, #CCB70D for yellow and #04D50D for green). The background is a bmp file containing the color gradient. The color loss happens whether the background is a gradient as the sample, a black canvas, a white canvas, a transparent canvas, even when there is not a background set. With black background With transparent background With a white background Without a background set With pixel format in Format32bppArgb I've tried multiple bitmap color deeps, output formats, compression level, etc. but none of them seems to work. Any ideas? This is a excerpt of the source code: Bitmap bmp = new Bitmap(w, h, System.Drawing.Imaging.PixelFormat.Format32bppPArgb); Image bgimage = (Image) HttpContext.GetGlobalResourceObject("GraphicResources", "GaugeBackgroundImage"); Canvas control_canvas = new Canvas(); .... //the routine that makes the gauge .... control_canvas.DrawToBitmap(bmp, new Rectangle(0, 0, w, h));

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• PoptorootViewController fails then removes all Viewcontrollers

  - by Spyker

  Trying to fix a very strange error, i have 3 view controllers that start from the app delegate and push each other accordingly. The 3rd view controller then has a toolbar button that calls the code here: -(void)showEventBrowser; { accelManeger.delegate = nil; NSLog(@"%u",[self.navigationController.viewControllers count]); [self.navigationController popToRootViewControllerAnimated:NO]; } This works the first time round but when i come back to this view controller and try again. Firstly it reports that there are 3 view controllers on the stack. It then deallocs the 2nd view controller in the stack and doesnt crash but will not go any further. If i hit the button again it says there are no view controllers on the stack and fails to respond. I have logs for all the viewdid, viewwill, e.t.c in each view controller and there appears to be no odd behaviour. Also no memory warnings from any view controllers. Why would this work once through but not the second time ?

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• JConsole does not connect when a program is waiting for a console input

  - by Calm Storm

  Hi, I have a problem similar to the one mentioned here. I have a program which launches a selenium browser and refreshes it every 2 seconds. My idea here was to monitor the memory usage of my application as the page is being hit. This console program does a "System.in.read" and when a user presses enter key, this stops the browser refresh thread. I run the program and it runs as I would expect it to. But when I fire jconsole and attach it to the process, it looks like jconsole waits forever to attach. This is because of the "System.in.read", apparently as shown in the JConsole source. In my code it makes perfect sense for me to terminte the browser when user presses something so is there any alternative available at all ? (Posted code sample below) package com.ekanathk; import java.util.ArrayList; import java.util.List; import org.junit.Test; public class MultiThread { @Test public void testSimple() throws Exception { List<Integer> x = new ArrayList<Integer>(); for(int i = 0; i < 1000; i++) { x.add(i); } System.out.print("Press Enter to stop (try attach a jconsole now...."); System.in.read(); } } The problem here seems to be that any System.in.read (either in Main thread or any threads) seems to completely block jconsole. I guess the problem essentially boils down to multiple threads requesting system inputs at the same time? Is there a solution ?

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• Why do people say that Ruby is slow?

  - by stephen murdoch

  I like Ruby on Rails and I use it for all my web development projects. A few years ago there was a lot of talk about Rails being a memory hog and about how it didn't scale very well but these suggestions were put to bed by Gregg Pollack here. Lately though, I've been hearing people saying that Ruby itself is slow. Why is Ruby considered slow? I do not find Ruby to be slow but then again, I'm just using it to make simple CRUD apps and company blogs. What sort of projects would I need to be doing before I find Ruby becoming slow? Or is this slowness just something that affects all programming languages? What are your options as a Ruby programmer if you want to deal with this "slowness"? Which version of Ruby would best suit an application like Stack Overflow where speed is critical and traffic is intense? The questions are subjective, and I realise that architectural setup (EC2 vs standalone servers etc) makes a big difference but I'd like to hear what people think about Ruby being slow. Finally, I can't find much news on Ruby 2.0 - I take it we're a good few years away from that then?

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• JConsole does not connect when a program (running in eclipse) is waiting for a console input

  - by Calm Storm

  Hi, I have a problem similar to the one mentioned here. I have a program which launches a selenium browser and refreshes it every 2 seconds. My idea here was to monitor the memory usage of my application as the page is being hit. This console program does a "System.in.read" and when a user presses enter key, this stops the browser refresh thread. I run the program and it runs as I would expect it to. But when I fire jconsole and attach it to the process, it looks like jconsole waits forever to attach. This is because of the "System.in.read", apparently as shown in the JConsole source. In my code it makes perfect sense for me to terminte the browser when user presses something so is there any alternative available at all ? (Posted code sample below) package com.ekanathk; import java.util.ArrayList; import java.util.List; import org.junit.Test; public class MultiThread { @Test public void testSimple() throws Exception { List<Integer> x = new ArrayList<Integer>(); for(int i = 0; i < 1000; i++) { x.add(i); } System.out.print("Press Enter to stop (try attach a jconsole now...."); System.in.read(); } } The problem here seems to be that any System.in.read (either in Main thread or any threads) seems to completely block jconsole. I guess the problem essentially boils down to multiple threads requesting system inputs at the same time? Is there a solution ? UPDATE 1: It seems this works fine when launching the class from a command line, however when I run from eclipse, jconsole cant connect. Any reasons ?

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• ASP.NET 2.0 and COM Port Communication

  - by theaviator

  ASP.NET 2.0 and COM Port Communication Hello Guys, I have a managed DLL which communicates with the devices attached on COM/Serial ports. The desktop Winforms application sends requests on ports and receives/stores data in memory. In Winforms app I have added a reference to DLL and I am using the methods. This works well. Now, there is a situation where I need to show this data from serial/com port on a web-page. And also users should be able to send requests to the ports using this DLL. I have made a web app in ASP.NET (2.0). Added a reference to the DLL. I am able to use this DLL, the DLL communicates on the COM upon button click on web-page and also the response is shown on web page. However I am not happy with the approach and strongly feel that this is a bad approach. Also the development server crashes after 3 -4 requests. What is the best approach in this scenario. If I use a windows service then how would my ASP.net app will communicate with the Weindows service. Or can this be easily done using WCF. I have not used WCF any time nor any of .net remoting technique. Please suggest me the best architecture in this scenario. Thank you

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• priority queue with limited space: looking for a good algorithm

  - by SigTerm

  This is not a homework. I'm using a small "priority queue" (implemented as array at the moment) for storing last N items with smallest value. This is a bit slow - O(N) item insertion time. Current implementation keeps track of largest item in array and discards any items that wouldn't fit into array, but I still would like to reduce number of operations further. looking for a priority queue algorithm that matches following requirements: queue can be implemented as array, which has fixed size and _cannot_ grow. Dynamic memory allocation during any queue operation is strictly forbidden. Anything that doesn't fit into array is discarded, but queue keeps all smallest elements ever encountered. O(log(N)) insertion time (i.e. adding element into queue should take up to O(log(N))). (optional) O(1) access for *largest* item in queue (queue stores *smallest* items, so the largest item will be discarded first and I'll need them to reduce number of operations) Easy to implement/understand. Ideally - something similar to binary search - once you understand it, you remember it forever. Elements need not to be sorted in any way. I just need to keep N smallest value ever encountered. When I'll need them, I'll access all of them at once. So technically it doesn't have to be a queue, I just need N last smallest values to be stored. I initially thought about using binary heaps (they can be easily implemented via arrays), but apparently they don't behave well when array can't grow anymore. Linked lists and arrays will require extra time for moving things around. stl priority queue grows and uses dynamic allocation (I may be wrong about it, though). So, any other ideas?

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• What would be the safest way to store objects of classes derived from a common interface in a common

  - by Svenstaro

  I'd like to manage a bunch of objects of classes derived from a shared interface class in a common container. To illustrate the problem, let's say I'm building a game which will contain different actors. Let's call the interface IActor and derive Enemy and Civilian from it. Now, the idea is to have my game main loop be able to do this: // somewhere during init std::vector<IActor> ActorList; Enemy EvilGuy; Civilian CoolGuy; ActorList.push_back(EvilGuy); ActorList.push_back(CoolGuy); and // main loop while(!done) { BOOST_FOREACH(IActor CurrentActor, ActorList) { CurrentActor.Update(); CurrentActor.Draw(); } } ... or something along those lines. This example obviously won't work but that is pretty much the reason I'm asking here. I'd like to know: What would be the best, safest, highest-level way to manage those objects in a common heterogeneous container? I know about a variety of approaches (Boost::Any, void*, handler class with boost::shared_ptr, Boost.Pointer Container, dynamic_cast) but I can't decide which would be the way to go here. Also I'd like to emphasize that I want to stay away as far as possible from manual memory management or nested pointers. Help much appreciated :).

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• Handling dependencies with IoC that change within a single function call

  - by Jess

  We are trying to figure out how to setup Dependency Injection for situations where service classes can have different dependencies based on how they are used. In our specific case, we have a web app where 95% of the time the connection string is the same for the entire Request (this is a web application), but sometimes it can change. For example, we might have 2 classes with the following dependencies (simplified version - service actually has 4 dependencies): public LoginService (IUserRepository userRep) { } public UserRepository (IContext dbContext) { } In our IoC container, most of our dependencies are auto-wired except the Context for which I have something like this (not actual code, it's from memory ... this is StructureMap): x.ForRequestedType().Use() .WithCtorArg("connectionString").EqualTo(Session["ConnString"]); For 95% of our web application, this works perfectly. However, we have some admin-type functions that must operate across thousands of databases (one per client). Basically, we'd want to do this: public CreateUserList(IList<string> connStrings) { foreach (connString in connStrings) { //first create dependency graph using new connection string ???? //then call service method on new database _loginService.GetReportDataForAllUsers(); } } My question is: How do we create that new dependency graph for each time through the loop, while maintaining something that can easily be tested?

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• PHP readfile() and large downloads

  - by Nirmal

  While setting up an online file management system, and now I have hit a block. I am trying to push the file to the client using this modified version of readfile: function readfile_chunked($filename,$retbytes=true) { $chunksize = 1*(1024*1024); // how many bytes per chunk $buffer = ''; $cnt =0; // $handle = fopen($filename, 'rb'); $handle = fopen($filename, 'rb'); if ($handle === false) { return false; } while (!feof($handle)) { $buffer = fread($handle, $chunksize); echo $buffer; ob_flush(); flush(); if ($retbytes) { $cnt += strlen($buffer); } } $status = fclose($handle); if ($retbytes && $status) { return $cnt; // return num. bytes delivered like readfile() does. } return $status; } But when I try to download a 13 MB file, it's just breaking at 4 MB. What would be the issue here? It's definitely not the time limit of any kind because I am working on a local network and speed is not an issue. The memory limit in PHP is set to 300 MB. Thank you for any help.

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• Source of UIView Implicit Animation delay?

  - by iPhoneToucher

  I have a block of UIView animation code that looks like this: [UIView beginAnimations:@"pushView" context:nil]; [UIView setAnimationDelay:0]; [UIView setAnimationDuration:.5]; [UIView setAnimationDelegate:self]; [UIView setAnimationWillStartSelector:@selector(animationWillStart)]; view.frame = CGRectMake(0, 0, 320, 416); [UIView commitAnimations]; The code basically mimics the animation of a ModalView presentation and is tied to a button on my interface. When the button is pressed, I get a long (.5 sec) delay (on iPod Touch...twice as fast on iPhone 3GS) before the animationWillStart: actually gets called. My app has lots going on besides this, but I've timed various points of my code and the delay definitely occurs at this block. In other words, a timestamp immediately before this code block and a timestamp when animationWillStart: gets called shows a .5 sec difference. I'm not too experienced with Core Animation and I'm just trying to figure out what the cause of the delay is...Memory use is stable when the animation starts and CoreAnimation FPS seems to be fine in Instruments. The view that gets animated does have upwards of 20 total subviews, but if that were the issue wouldn't it cause choppiness after the animation starts, rather than before? Any ideas?

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• Files not waiting for each other

  - by Sunny

  I have two batch files as follows in which file2.bat is dependent on file1.bat's output: file1.bat @ECHO OFF setlocal enabledelayedexpansion SET "keystring1=" ( FOR /f "delims=" %%a IN ( Source.txt ) DO ( ECHO %%a|FIND "Appprocess.exe" >NUL IF NOT ERRORLEVEL 1 SET keystring1=%%a FOR %%b IN (App1 App2 App3 App4 App5 App6 ) DO ( ECHO %%a|FIND "%%b" >NUL IF NOT ERRORLEVEL 1 IF DEFINED keystring1 CALL ECHO(%%keystring1%% %%b&SET "keystring1=" )))>result.txt GOTO :EOF file2.bat @echo off setlocal enabledelayedexpansion (for /f "tokens=1,2" %%a in (memory.txt) do ( for /f "tokens=5" %%c in ('find " %%a " ^< result.txt ') do echo %%c %%b ))> new.txt file1.bat usually takes 60 sec to complete its execution. In master.bat file i am calling above two files as: call file1.bat call file2.bat but file2.bat is not waiting for file1.bat to complete its execution. Even , i tried to call file2.bat within file1.bat as below but still its not waiting for file1.bat to get completed: @ECHO OFF setlocal enabledelayedexpansion SET "keystring1=" ( FOR /f "delims=" %%a IN ( Source.txt ) DO ( ECHO %%a|FIND "HsvDataSource.exe" >NUL IF NOT ERRORLEVEL 1 SET keystring1=%%a FOR %%b IN (EUHFMPROD USHFMPROD TL2TEST GSHFMPROD TL2PROD GSARCH1213 TL2FY13) DO ( ECHO %%a|FIND "%%b" >NUL IF NOT ERRORLEVEL 1 IF DEFINED keystring1 CALL ECHO(%%keystring1%% %%b&SET "keystring1=" )))>file2.txt GOTO :EOF call file1.bat I also tried below start option, but no effect.: start file1.bat /wait call file2.bat Not getting ..why its happening..?

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• how useful is Turing completeness? are neural nets turing complete?

  - by Albert

  While reading some papers about the Turing completeness of recurrent neural nets (for example: Turing computability with neural nets, Hava T. Siegelmann and Eduardo D. Sontag, 1991), I got the feeling that the proof which was given there was not really that practical. For example the referenced paper needs a neural network which neuron activity must be of infinity exactness (to reliable represent any rational number). Other proofs need a neural network of infinite size. Clearly, that is not really that practical. But I started to wonder now if it does make sense at all to ask for Turing completeness. By the strict definition, no computer system nowadays is Turing complete because none of them will be able to simulate the infinite tape. Interestingly, programming language specification leaves it most often open if they are turing complete or not. It all boils down to the question if they will always be able to allocate more memory and if the function call stack size is infinite. Most specification don't really specify this. Of course all available implementations are limited here, so all practical implementations of programming languages are not Turing complete. So, what you can say is that all computer systems are just equally powerful as finite state machines and not more. And that brings me to the question: How useful is the term Turing complete at all? And back to neural nets: For any practical implementation of a neural net (including our own brain), they will not be able to represent an infinite number of states, i.e. by the strict definition of Turing completeness, they are not Turing complete. So does the question if neural nets are Turing complete make sense at all? The question if they are as powerful as finite state machines was answered already much earlier (1954 by Minsky, the answer of course: yes) and also seems easier to answer. I.e., at least in theory, that was already the proof that they are as powerful as any computer.

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• Compiling C lib and OCaml exe using it, all using ocamlfind

  - by Magnus

  I'm trying to work out how to use ocamlfind to compile a C library and an OCaml executable using that C library. I put together a set of rather silly example files. % cat sillystubs.c #include <stdio.h> #include <caml/mlvalues.h> #include <caml/memory.h> #include <caml/alloc.h> #include <caml/custom.h> value caml_silly_silly( value unit ) { CAMLparam1( unit ); printf( "%s\n", __FILE__ ); CAMLreturn( Val_unit ); } % cat silly.mli external silly : unit -> unit = "silly_silly" % cat foo.ml open Silly open String let _ = print_string "About to call into silly"; silly (); print_string "Called into silly" I believe the following is the way to compile up the library: % ocamlfind ocamlc -c sillystubs.c % ar rc libsillystubs.a sillystubs.o % ocamlfind ocamlc -c silly.mli % ocamlfind ocmalc -a -o silly.cma -ccopt -L${PWD} -cclib -lsillystubs Now I don't seem to be able to use the created library though: % ocamlfind ocamlc -custom -o foo foo.cmo silly.cma /usr/bin/ld: cannot find -lsillystubs collect2: ld returned 1 exit status File "_none_", line 1, characters 0-1: Error: Error while building custom runtime system The OCaml tools are somewhat mysterious to me, so any pointers would be most welcome.

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• Creating a DataTable by filtering another DataTable

  - by Jeff Dege

  I'm working on a system that currently has a fairly complicated function that returns a DataTable, which it then binds to a GUI control on a ASP.NET WebForm. My problem is that I need to filter the data returned - some of the data that is being returned should not be displayed to the user. I'm aware of DataTable.select(), but that's not really what I need. First, it returns an array of DataRows, and I need a DataTable, so I can databind it to the GUI control. But more importantly, the filtering I need to do isn't something that can be easily put into a simple expression. I have an array of the elements which I do not want displayed, and I need to compare each element from the DataTable against that array. What I could do, of course, is to create a new DataTable, reading everything out of the original, adding to the new what is appropriate, then databinding the new to the GUI control. But that just seems wrong, somehow. In this case, the number of elements in the original DataTable aren't likely to be enough that copying them all in memory is going to cause too much trouble, but I'm wondering if there is another way. Does the .NET DataTable have functionality that would allow me to filter via a callback function?

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• NonStop ODBC: how the connections (ODBC servers) are assigned to CPUs?

  - by Vladimir Dyuzhev

  We have an ODBC pool running on a NonStop server. The pool is connected to SQL/MX. This pool is used by a few external Java applications, each of which has an JDBC pool connected to ODBC pool (e.g. 14 connections per application). With time (after a few application recycles) we see an imbalance between CPUs -- some have 8 ODBC processes running, some only 5. That leads to CPU time imbalance too. Up to this point we assumed that a CPU is assigned to ODBC process in round-robin fashion. That would maintain the number of ODBC processes more or less equally distributed. It's not the case though. Is there any information on how ODBC pool decided which CPU to choose for every new allocated process? Does it look at CPU load? Available memory? Something else? Sadly, even HP's own people (available to us, that is) couldn't answer those questions with certainty. :-(

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• should std::auto_ptr<>::operator = reset / deallocate its existing pointee ?

  - by afriza

  I read here about std::auto_ptr<::operator= Notice however that the left-hand side object is not automatically deallocated when it already points to some object. You can explicitly do this by calling member function reset before assigning it a new value. However, when I read the source code for header file C:\Program Files\Microsoft Visual Studio 8\VC\ce\include\memory template<class _Other> auto_ptr<_Ty>& operator=(auto_ptr<_Other>& _Right) _THROW0() { // assign compatible _Right (assume pointer) reset(_Right.release()); return (*this); } auto_ptr<_Ty>& operator=(auto_ptr<_Ty>& _Right) _THROW0() { // assign compatible _Right (assume pointer) reset(_Right.release()); return (*this); } auto_ptr<_Ty>& operator=(auto_ptr_ref<_Ty> _Right) _THROW0() { // assign compatible _Right._Ref (assume pointer) _Ty **_Pptr = (_Ty **)_Right._Ref; _Ty *_Ptr = *_Pptr; *_Pptr = 0; // release old reset(_Ptr); // set new return (*this); } What is the correct/standard behavior? How do other STL implementations behave?

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• hudson.util.ProcessTreeTest test error

  - by senzacionale

  error: Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.011 sec Running hudson.util.ProcessTreeTest Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.181 sec <<< FAILURE! Running hudson.model.LoadStatisticsTest Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 2.089 sec Running hudson.util.ArgumentListBuilderTest Tests run: 5, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.053 sec Running hudson.util.RobustReflectionConverterTest Tests run: 2, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.029 sec Running hudson.util.VersionNumberTest Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.074 sec Running hudson.util.CyclicGraphDetectorTest Tests run: 3, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.038 sec Results : Tests in error: testRemoting(hudson.util.ProcessTreeTest) Tests run: 102, Failures: 0, Errors: 1, Skipped: 0 [INFO] ------------------------------------------------------------------------ [ERROR] BUILD FAILURE [INFO] ------------------------------------------------------------------------ [INFO] There are test failures. Please refer to D:\PROJEKTI\Maven\hudson\main\core\target\surefire-reports for the individual test results. [INFO] ------------------------------------------------------------------------ [INFO] For more information, run Maven with the -e switch [INFO] ------------------------------------------------------------------------ [INFO] Total time: 17 minutes 58 seconds [INFO] Finished at: Fri Jun 11 21:04:46 CEST 2010 [INFO] Final Memory: 85M/152M [INFO] ------------------------------------------------------------------------ error log: ------------------------------------------------------------------------------- Test set: hudson.util.ProcessTreeTest ------------------------------------------------------------------------------- Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.181 sec <<< FAILURE! testRemoting(hudson.util.ProcessTreeTest) Time elapsed: 0.169 sec <<< ERROR! org.jvnet.winp.WinpException: Failed to read environment variable table error=299 at .\envvar-cmdline.cpp:114 at org.jvnet.winp.Native.getCmdLineAndEnvVars(Native Method) at org.jvnet.winp.WinProcess.parseCmdLineAndEnvVars(WinProcess.java:114) at org.jvnet.winp.WinProcess.getEnvironmentVariables(WinProcess.java:109) at hudson.util.ProcessTree$Windows$1.getEnvironmentVariables(ProcessTree.java:419) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at hudson.remoting.RemoteInvocationHandler$RPCRequest.perform(RemoteInvocationHandler.java:274) at hudson.remoting.RemoteInvocationHandler$RPCRequest.call(RemoteInvocationHandler.java:255) at hudson.remoting.RemoteInvocationHandler$RPCRequest.call(RemoteInvocationHandler.java:215) at hudson.remoting.UserRequest.perform(UserRequest.java:114) at hudson.remoting.UserRequest.perform(UserRequest.java:48) at hudson.remoting.Request$2.run(Request.java:270) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) at java.util.concurrent.FutureTask.run(FutureTask.java:138) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:619) does anyone have any idea what can be wrong in test? Regards

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• Behavior of retained propertie while holder is retained

  - by Aurélien Vallée

  Hello everyone, I am a beginner ObjectiveC programmer, coming from the C++ world. I find it very difficult to understand the memory management offered by NSObject :/ Say I have the following class: @interface User : NSObject { NSString* name; } @property (nonatomic,retain) NSString* name; - (id) initWithName: (NSString*) theName; - (void) release; @end @implementation User @synthetise name - (id) initWithName: (NSString*) theName { if ( self = [super init] ) { [self setName:theName]; } return self; } - (void) release { [name release]; [super release]; } @end No considering the following code, I can't understand the retain count results: NSString* name = [[NSString alloc] initWithCString:/*C string from sqlite3*/]; // (1) name retainCount = 1 User* user = [[User alloc] initWithName:name]; // (2) name retainCount = 2 [whateverMutableArray addObject:user]; // (3) name retainCount = 2 [user release]; // (4) name retainCount = 1 [name release]; // (5) name retainCount = 0 At (4), the retain count of name decreased from 2 to 1. But that's not correct, there is still the instance of user inside the array that points to name ! The retain count of a variable should only decrease when the retain count of a referring variable is 0, that is, when it is dealloced, not released.

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• Best practices for Java logging from multiple threads?

  - by Jason S

  I want to have a diagnostic log that is produced by several tasks managing data. These tasks may be in multiple threads. Each task needs to write an element (possibly with subelements) to the log; get in and get out quickly. If this were a single-task situation I'd use XMLStreamWriter as it seems like the best match for simplicity/functionality without having to hold a ballooning XML document in memory. But it's not a single-task situation, and I'm not sure how to best make sure this is "threadsafe", where "threadsafe" in this application means that each log element should be written to the log correctly and serially (one after the other and not interleaved in any way). Any suggestions? I have a vague intuition that the way to go is to use a queue of log elements (with each one able to be produced quickly: my application is busy doing real work that's performance-sensitive), and have a separate thread which handles the log elements and sends them to a file so the logging doesn't interrupt the producers. The logging doesn't necessarily have to be XML, but I do want it to be structured and machine-readable. edit: I put "threadsafe" in quotes. Log4j seems to be the obvious choice (new to me but old to the community), why reinvent the wheel...

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