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• Should a new language compiler target the JVM?

  - by Pindatjuh

  I'm developing a new language. My initial target was to compile to native x86 for the Windows platform, but now I am in doubt. I've seen some new languages target the JVM (most notable Scala and Clojure). Ofcourse it's not possible to port every language easily to the JVM; to do so, it may lead to small changes to the language and it's design. So that's the reason behind this doubt, and thus this question: Is targetting the JVM a good idea, when creating a compiler for a new language? Or should I stick with x86? I have experience in generating JVM bytecode. Are there any workarounds to JVM's GC? The language has deterministic implicit memory management. How to produce JIT-compatible bytecode, such that it will get the highest speedup? Is it similar to compiling for IA-32, such as the 4-1-1 muops pattern on Pentium? I can imagine some advantages (please correct me if I'm wrong): JVM bytecode is easier than x86. Like x86 communicates with Windows, JVM communicates with the Java Foundation Classes. To provide I/O, Threading, GUI, etc. Implementing "lightweight"-threads.I've seen a very clever implementation of this at http://www.malhar.net/sriram/kilim/. Most advantages of the Java Runtime (portability, etc.) The disadvantages, as I imagined, are: Less freedom? On x86 it'll be more easy to create low-level constructs, while JVM has a higher level (more abstract) processor. Most disadvantages of the Java Runtime (no native dynamic typing, etc.)

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• When do instance variables get initialized and values assigned?

  - by AKh

  When doees the instance variable get initialized? Is it after the constructor block is done or before it? Consider this example: public abstract class Parent { public Parent(){ System.out.println("Parent Constructor"); init(); } public void init(){ System.out.println("parent Init()"); } } public class Child extends Parent { private Integer attribute1; private Integer attribute2 = null; public Child(){ super(); System.out.println("Child Constructor"); } public void init(){ System.out.println("Child init()"); super.init(); attribute1 = new Integer(100); attribute2 = new Integer(200); } public void print(){ System.out.println("attribute 1 : " +attribute1); System.out.println("attribute 2 : " +attribute2); } } public class Tester { public static void main(String[] args) { Parent c = new Child(); ((Child)c).print(); } } OUTPUT: Parent Constructor Child init() parent Init() Child Constructor attribute 1 : 100 attribute 2 : null When the memory for the atribute 1 & 2 are allocated in the heap ? Curious to know why is attribute 2 is NULL ? Are there any design flaws?

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• document.onclick settimeout function javascript help

  - by Jamex

  Hi, I have a document.onclick function that I would like to have a delay. I can't seem to get the syntax right. my original code is <script type="text/javascript"> document.onclick=check; function check(e){do something} I tried the below, but that code is incorrect, the function did not execute and nothing happened. <script type="text/javascript"> document.onclick=setTimeout("check", 1000); function check(e){do something} I tried the next set, the function got executed, but no delay. <script type="text/javascript"> setTimeout(document.onclick=check, 1000); function check(e){do something} what is the correct syntax for this code. TIA Edit: The solutions were all good, my problem was that I use the function check to obtain the id of the element being clicked on. But after the delay, there is no "memory" of what was being clicked on, so the rest of the function does not get executed. Jimr wrote the short code to preserve clicked event. The code that is working is // Delay execution of event handler function "f" by "time" ms. document.onclick = makeDelayedHandler(check, 250); function makeDelayedHandler( f, time) { return function( e ) {setTimeout(function() {f( e );}, time ); }; } function check(e){ var click = (e && e.target) || (event && event.srcElement); . . . Thank you all.

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• Passing data between ViewControllers versus doing local Fetch in each VC

  - by Tofrizer

  Hi All, I'm developing an iPhone app using Core Data and I'm looking for some general advice and recommendations on whether its acceptable to pass data between ViewControllers versus doing a local fetch in each ViewController as you navigate to it. Ordinarily I would say it all depends on various factors (e.g. performance etc) but the passing data approach is so prevalent in my app and I'm spooked by all the stories about Apple rejecting apps because of not conforming to their standard guidelines. So let me put another way -- is it non-standard to pass data between VC's? The reason I pass data so much is because each ViewController is just another view on to data present in my object model / graph. Once I have a handle on my first object in the first view controller (which I of course do have to fetch), I can use the existing object composition / relationships to drill down into the next level of detail into data and so I just pass these objects to the next VC. Separately, one possible downside with this passing-data-to-each-VC approach is I don't benefit from (what I perceive to be) the optimisation/benefits that NSFetchedResultsController provides in terms of efficient memory usage and section handling. My app is read-only but I do have one table with 5000 rows and I'm curious if I am missing out on NSFetchedResultsController benefits. Any thoughts on this as well? Can I somehow still benefit from NSFetchedResultsController goodness without having to do a full fetch (as I would have already passed in the data from my previous VC)? Thanks a lot.

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• Why execution of a portion of code loaded from external file is not halted by the OS?

  - by menjaraz

  I've harnessed a project released on internet a long time ago. Here comes the details, all irrelevant things being stripped off for sake of concision and clarity. A binary file whose content is descibed below HEX DUMP: 55 89 E5 83 EC 08 C7 45 FC 00 00 00 00 8B 45 FC 3B 45 10 72 02 EB 19 8B 45 FC 8B 55 0C 01 C2 8B 45 FC 03 45 08 8A 00 88 02 8D 45 FC FF 00 EB DD C6 45 FA 00 83 7D 10 01 76 6C 80 7D FA 00 74 02 EB 64 C6 45 FA 01 C7 45 FC 00 00 00 00 8B 45 10 48 39 45 FC 72 02 EB E2 8B 45 FC 8B 4D 0C 01 C1 8B 45 FC 03 45 0C 8D 50 01 8A 01 3A 02 73 30 8B 45 FC 03 45 0C 8A 00 88 45 FB 8B 45 FC 8B 55 0C 01 C2 8B 45 FC 03 45 0C 40 8A 00 88 02 8B 45 FC 03 45 0C 8D 50 01 8A 45 FB 88 02 C6 45 FA 00 8D 45 FC FF 00 EB A7 C9 C2 0C 00 90 90 90 90 90 90 is loaded into memory and executed using the following method snippet var MySrcArray, MyDestArray: array [1 .. 15] of Byte; // ... MyBuffer: Pointer; TheProc: procedure; SortIt: procedure(ASrc, ADest: Pointer; ASize: LongWord); stdcall; begin // Initialization of MySrcArray with random Bytes and display here ... // Instructions of loading of the binary file into MyBuffer using merely **GetMem** here ... @SortIt := MyBuffer; try SortIt(@MySrcArray, @MyDestArray, 15); // Display of MyDestArray (The outcome of the processing !) except // Invalid code error handling end; // Cleaning code here ... end; works like a charm on my box. My Question: How comes it works without using VirtualAlloc and/or VirtualProtect?

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• Legitimate uses of the Function constructor

  - by Marcel Korpel

  As repeatedly said, it is considered bad practice to use the Function constructor (also see the ECMAScript Language Specification, 5th edition, § 15.3.2.1): new Function ([arg1[, arg2[, … argN]],] functionBody) (where all arguments are strings containing argument names and the last (or only) string contains the function body). To recapitulate, it is said to be slow, as explained by the Opera team: Each time […] the Function constructor is called on a string representing source code, the script engine must start the machinery that converts the source code to executable code. This is usually expensive for performance – easily a hundred times more expensive than a simple function call, for example. (Mark ‘Tarquin’ Wilton-Jones) Though it's not that bad, according to this post on MDC (I didn't test this myself using the current version of Firefox, though). Crockford adds that [t]he quoting conventions of the language make it very difficult to correctly express a function body as a string. In the string form, early error checking cannot be done. […] And it is wasteful of memory because each function requires its own independent implementation. Another difference is that a function defined by a Function constructor does not inherit any scope other than the global scope (which all functions inherit). (MDC) Apart from this, you have to be attentive to avoid injection of malicious code, when you create a new Function using dynamic contents. Lots of disadvantages and it is intelligible that ECMAScript 5 discourages the use of the Function constructor by throwing an exception when using it in strict mode (§ 13.1). That said, T.J. Crowder says in an answer that [t]here's almost never any need for the similar […] new Function(...), either, again except for some advanced edge cases. So, now I am wondering: what are these “advanced edge cases”? Are there legitimate uses of the Function constructor?

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• ColdFusion 8 Slow Performance

  - by JoeBob

  We have started a new CF8 app and it is running dog slow. A test where we go around ColdFusion (queries within a database utility) show normal speed (80ms). CF8 returns the same query in something like 60 to 80 seconds! I have been looking online and seeing lots of posts about CF8 and performance problems, but don't get any overall sense of a solution; just lots of people trying things and saying that they didn't have the problem with CF7. We are also seeing instability on the server, and some errors relating to garbage collection and the memory heap. We have a number of other applications running on CF8 and they perform adequately...our programmer is not an expert or a guru, he just plugs away. We have isolated this down to a single query that takes forever to return, so it is not a complicated test. Are there any known CF8 problems or obvious tweaks that we should consider trying? If we have to start over and learn a new environment, I will never make deadline. JoeBob

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• Win32 DLL importing issues (DllMain)

  - by brady

  I have a native DLL that is a plug-in to a different application (one that I have essentially zero control of). Everything works just great until I link with an additional .lib file (links my DLL to another DLL named ABQSMABasCoreUtils.dll). This file contains some additional API from the parent application that I would like to utilize. I haven't even written any code to use any of the functions exported but just linking in this new DLL is causing problems. Specifically I get the following error when I attempt to run the program: The application failed to initialize properly (0xc0000025). Clock on OK to terminate the application. I believe I have read somewhere that this is typically due to a DllMain function returning FALSE. Also, the following message is written to the standard output: ERROR: Memory allocation attempted before component initialization I am almost 100% sure this error message is coming from the application and is not some type of Windows error. Looking into this a little more (aka flailing around and flipping every switch I know of) I linked with /MAP turned on and found this in the resulting .map file: 0001:000af220 ??3@YAXPEAX@Z 00000001800b0220 f ABQSMABasCoreUtils_import:ABQSMABasCoreUtils.dll 0001:000af226 ??2@YAPEAX_K@Z 00000001800b0226 f ABQSMABasCoreUtils_import:ABQSMABasCoreUtils.dll 0001:000af22c ??_U@YAPEAX_K@Z 00000001800b022c f ABQSMABasCoreUtils_import:ABQSMABasCoreUtils.dll 0001:000af232 ??_V@YAXPEAX@Z 00000001800b0232 f ABQSMABasCoreUtils_import:ABQSMABasCoreUtils.dll If I undecorate those names using "undname" they give the following (same order): void __cdecl operator delete(void * __ptr64) void * __ptr64 __cdecl operator new(unsigned __int64) void * __ptr64 __cdecl operator new[](unsigned __int64) void __cdecl operator delete[](void * __ptr64) I am not sure I understand how anything from ABQSMABasCoreUtils.dll can exist within this .map file or why my DLL is even attempting to load ABQSMABasCoreUtils.dll if I don't have any code that references this DLL. Can anyone help me put this information together and find out why this isn't working? For what it's worth I have confirmed via "dumpbin" that the parent application imports the same DLL (ABQSMABasCoreUtils.dll), so it is being loaded no matter what. I have also tried delay loading this DLL in my DLL but that did not change the results.

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• Transitioning from FlexBuilder 3 to FlashBuilder 4 ... there and back again.

  - by Robusto

  It's growing pains time again. Some of our stuff requires FlashBuilder 4 and some still requires FlexBuilder 3. Both are installed OK, and no projects use both IDEs. The trouble is, when I go back to work on a FlexBuilder 3 project it takes freakin' forever to build and I get weird errors like these: This doesn't seem to cause any identifiable problems except to throw up a modal dialog at various points in the build process, forcing user interaction. But I do notice that memory fills up fast in FB3 and generally FB3 starts behaving strangely and ultimately quits once it gets up over 700MB. This is only a temporary bridge situation until we get all projects into FB4, but "temporary" could mean weeks if not months. Does anyone have any advice for how to get through this bridge period? Is there anything I can do to make these two IDEs work and play well together? Failing that, does anyone know what "java.lang.String" is the "reason" for the problem? Does Eclipse have a resource bundle somewhere that is getting corrupted when i go back and forth between the two?

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• Elegant way of parsing Data files for Simulation

  - by sc_ray

  I am working on this project where I need to read in a lot of data from .dat files and use the data to perform simulations. The data in my .dat file looks as follows: DeviceID InteractingDeviceID InteractionStartTime InteractionEndTime 1 2 1101 1105 1,2 1101 and 1105 are tab delimited and it means Device 1 interacted with Device 2 at 1101 ms and ended the interaction at 1105ms. I have a trace data sets that compile thousands of such interactions and my job is to analyze these interactions. The first step is to parse the file. The language of choice is C++. The approach I was thinking of taking was to read the file, for every line that's read create a Device Object. This Device object will contain the property DeviceId and an array/vector of structs, that will contain a list of all the devices the given DeviceId interacted with over the course of the simulation.The struct will contain the Interacting Device Id, Interaction Start Time and Interaction End Time. I have a two fold question here: Is my approach correct? If I am on the right track, how do I rapidly parse these tab delimited data files and create Device objects without excessive memory overhead using C++? A push in the right direction will be much appreciated. Thanks

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• How to cache pages using background jobs ?

  - by Alexandre

  Definitions: resource = collection of database records, regeneration = processing these records and outputting the corresponding html Current flow: Receive client request Check for resource in cache If not in cache or cache expired, regenerate Return result The problem is that the regeneration step can tie up a single server process for 10-15 seconds. If a couple of users request the same resource, that could result in a couple of processes regenerating the exact same resource simultaneously, each taking up 10-15 seconds. Wouldn't it be preferrable to have the frontend signal some background process saying "Hey, regenerate this resource for me". But then what would it display to the user? "Rebuilding" is not acceptable. All resources would have to be in cache ahead of time. This could be a problem as the database would almost be duplicated on the filesystem (too big to fit in memory). Is there a way to avoid this? Not ideal, but it seems like the only way out. But then there's one more problem. How to keep the same two processes from requesting the regeneration of a resource at the same time? The background process could be regenerating the resource when a frontend asks for the regeneration of the same resource. I'm using PHP and the Zend Framework just in case someone wants to offer a platform-specific solution. Not that it matters though - I think this problem applies to any language/framework. Thanks!

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• How to find Tomcat's PID and kill it in python?

  - by 4herpsand7derpsago

  Normally, one shuts down Apache Tomcat by running its shutdown.sh script (or batch file). In some cases, such as when Tomcat's web container is hosting a web app that does some crazy things with multi-threading, running shutdown.sh gracefully shuts down some parts of Tomcat (as I can see more available memory returning to the system), but the Tomcat process keeps running. I'm trying to write a simple Python script that: Calls shutdown.sh Runs ps -aef | grep tomcat to find any process with Tomcat referenced If applicable, kills the process with kill -9 <PID> Here's what I've got so far (as a prototype - I'm brand new to Python BTW): #!/usr/bin/python # Imports import sys import subprocess # Load from imported module. if __init__ == "__main__": main() # Main entry point. def main(): # Shutdown Tomcat shutdownCmd = "sh ${TOMCAT_HOME}/bin/shutdown.sh" subprocess.call([shutdownCmd], shell=true) # Check for PID grepCmd = "ps -aef | grep tomcat" grepResults = subprocess.call([grepCmd], shell=true) if(grepResult.length > 1): # Get PID and kill it. pid = ??? killPidCmd = "kill -9 $pid" subprocess.call([killPidCmd], shell=true) # Exit. sys.exit() I'm struggling with the middle part - with obtaining the grep results, checking to see if their size is greater than 1 (since grep always returns a reference to itself, at least 1 result will always be returned, methinks), and then parsing that returned PID and passing it into the killPidCmd. Thanks in advance!

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• Minimal assembler program for CP/M 3.1 (z80)

  - by Andrew J. Brehm

  I seem to be losing the battle against my stupidity. This site explains the system calls under various versions of CP/M. However, when I try to use call 2 (C_WRITE, console output), nothing much happens. I have the following code. ORG 100h LD E,'a' LD C,2 CALL 5 CALL 0 I recite this here from memory. If there are typos, rest assured they were not in the original since the file did compile and I had a COM file to start. I am thinking the lines mean the following: Make sure this gets loaded at address 100h (0h to FFh being the zero page). Load ASCII 'a' into E register for system call 2. Load integer 2 into C register for system call 2. Make system call (JMP to system call is at address 5 in zero page). End program (Exit command is at address 0 in zero page). The program starts and exits with no problems. If I remove the last command, it hangs the computer (which I guess is also expected and shows that CALL 0 works). However, it does not print the ASCII character. (But it does print an extra new line, but the system might have done that.) How can I get my CP/M program to do what the system call is supposed to do? What am I doing wrong?

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• .net IHTTPHandler Streaming SQL Binary Data

  - by Yisman

  Hello everybody I am trying to implement an ihttphandeler for streaming files. files may be tiny thumbnails or gigantic movies the binaries r stored in sql server i looked at a lot of code online but something does not make sense isnt streaming supposed to read the data piece by piece and move it over the line? most of the code seems to first read the whole field from mssql to memory and then use streaming for the output writing wouldnt it b more eficient to actually stream from disk directly to http byte by byte (or buffered chunks?) heres my code so far but cant figure out the correct combination of the sqlreader mode and the stream object and the writing system Public Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest context.Response.BufferOutput = False Dim FileField=safeparam(context.Request.QueryString("FileField")) Dim FileTable=safeparam(context.Request.QueryString("FileTable")) Dim KeyField=safeparam(context.Request.QueryString("KeyField")) Dim FileKey=safeparam(context.Request.QueryString("FileKey")) Using connection As New SqlConnection(ConfigurationManager.ConnectionStrings("Main").ConnectionString) Using command As New SqlCommand("SELECT " & FileField & "Bytes," & FileField & "Type FROM " & FileTable & " WHERE " & KeyField & "=" & FileKey, connection) command.CommandType = Data.CommandType.Text enbd using end using end sub please be aware that this sql command also returns the file extension (pdf,jpg,doc...) in the second field of the query thank you all very much

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• Problem in accessing Windows shared folder on Ubuntu using terminal

  - by vikramtheone

  Hi Guys, Description I have 2 systems with me, one running on Windows(Host) and one on Ubuntu, both on a LAN. On the Windows(Host) I develop software intended for the Linux system and because the Linux system has little external memory, my idea to overcome this is by making the project folder on the Host side a Shared Folder with full access and access it on Ubuntu over the network. To achieve this, I have installed Samba on Ubuntu, when I go to Places -> Network I can see the shared project folder and I simply mount it. A link appears on the desktop. Next, using Nautilus I open the link and I can access the contents of the shared folder. Problem Even though I mount the shared project folder, I don't see it appearing in the /media or the /mnt folder, as a result of this I don't know what path to use to access this folder, from the terminal. For example: When, I mounted my USB stick, as expected, a link for the device appears on the Desktop and I also see a folder in the media folder. So, similarly, a mounted shared folder should have appeared on the /mnt folder, too. Can anyone suggest what I should do now? There are many posts around, but no solid solution for this problem. Help!!! :) Vikram

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• Is there a way to programatically check dependencies of an EXE?

  - by Mason Wheeler

  I've got a certain project that I build and distribute to users. I have two build configurations, Debug and Release. Debug, obviously, is for my use in debugging, but there's an additional wrinkle: the Debug configuration uses a special debugging memory manager, with a dependency on an external DLL. There's been a few times when I've accidentally built and distributed an installer package with the Debug configuration, and it's then failed to run once installed because the users don't have the special DLL. I'd like to be able to keep that from happening in the future. I know I can get the dependencies in a program by running Dependency Walker, but I'm looking for a way to do it programatically. Specifically, I have a way to run scripts while creating the installer, and I want something I can put in the installer script to check the program and see if it has a dependency on this DLL, and if so, cause the installer-creation process to fail with an error. I know how to create a simple CLI program that would take two filenames as parameters, and could run a DependsOn function and create output based on the result of it, but I don't know what to put in the DependsOn function. Does anyone know how I'd go about writing it?

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• using volatile keyword

  - by sap

  As i understand, if we declare a variable as volatile, then it will not be stored in the local cache. Whenever thread are updating the values, it is updated to the main memory. So, other threads can access the updated value. But in the following program both volatile and non-volatile variables are displaying same value. The volatile variable is not updated for the second thread. Can anybody plz explain this why testValue is not changed. class ExampleThread extends Thread { private int testValue1; private volatile int testValue; public ExampleThread(String str){ super(str); } public void run() { if (getName().equals("Thread 1 ")) { testValue = 10; testValue1= 10; System.out.println( "Thread 1 testValue1 : " + testValue1); System.out.println( "Thread 1 testValue : " + testValue); } if (getName().equals("Thread 2 ")) { System.out.println( "Thread 2 testValue1 : " + testValue1); System.out.println( "Thread 2 testValue : " + testValue); } } } public class VolatileExample { public static void main(String args[]) { new ExampleThread("Thread 1 ").start(); new ExampleThread("Thread 2 ").start(); } } output: Thread 1 testValue1 : 10 Thread 1 testValue : 10 Thread 2 testValue1 : 0 Thread 2 testValue : 0

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• How can I improve the performance of this double-for print?

  - by Florenc

  I have the following static method that prints the data imported from a 40.000 lines .xls spreadsheet. Now, it takes about 27 seconds to print the data in the console and the memory consumption is huge. import org.apache.poi.hssf.usermodel.*; import org.apache.poi.ss.usermodel.*; public static void printSheetData(List<List<HSSFCell>> sheetData) { for (int i = 0; i < sheetData.size(); i++) { List<HSSFCell> list = (List<HSSFCell>) sheetData.get(i); for (int j = 0; j < list.size(); j++) { HSSFCell cell = (HSSFCell) list.get(j); System.out.print(cell.toString()); if (j < list.size() - 1) { System.out.print(", "); } } System.out.println(""); } } Disclaimer: I know, I know large data belong to a database, don't print output in the console, premature optimization is the root of all evils...

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• Permissions on Mac OSX

  - by Linda

  I think that this is a permissions issue but I am not sure and I am not sure how to repair the problem. I have a new MacBook. I have 2 external drives that were previously used on another MacBook. I have a lot of folders and XCode projects on the external drives. When I try to work on the projects, there is a message similar to this: "This file is not writable. You may not be able to save your changes, but you will be able to Save a Copy somewhere else. Do you want to edit this file anyway?" If I make changes and try to close the project I get this error: "The project and user files project.pbxproj and macbook.pbxuser for project “thirdtry.xcodeproj” are not writeable and cannot be saved. Your changes will be lost if you close the project. You may need to SCM edit these files to gain writability." I have tried just to rename the folder but that permission is not allowed either unless I individually change permissions for every file in an XCode project. As you can imagine, this could be time consuming for tons of files and projects. I can copy the project into internal memory and can run it then after renaming the folder that contains all of the files. This defeats the purpose of having all of the projects on an external drive. Also, in XCode, there is no "Build and Run" there is only "Build and Debug" now. I don't know if this is related or not. Suggestions for how to repair all permissions to all files and folders on my external drives? What about the "Build and Debug" and no "Build and Run" choice? Thanks, Linda

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• Why doesn't gcc remove this check of a non-volatile variable?

  - by Thomas

  This question is mostly academic. I ask out of curiosity, not because this poses an actual problem for me. Consider the following incorrect C program. #include <signal.h> #include <stdio.h> static int running = 1; void handler(int u) { running = 0; } int main() { signal(SIGTERM, handler); while (running) ; printf("Bye!\n"); return 0; } This program is incorrect because the handler interrupts the program flow, so running can be modified at any time and should therefore be declared volatile. But let's say the programmer forgot that. gcc 4.3.3, with the -O3 flag, compiles the loop body (after one initial check of the running flag) down to the infinite loop .L7: jmp .L7 which was to be expected. Now we put something trivial inside the while loop, like: while (running) putchar('.'); And suddenly, gcc does not optimize the loop condition anymore! The loop body's assembly now looks like this (again at -O3): .L7: movq stdout(%rip), %rsi movl $46, %edi call _IO_putc movl running(%rip), %eax testl %eax, %eax jne .L7 We see that running is re-loaded from memory each time through the loop; it is not even cached in a register. Apparently gcc now thinks that the value of running could have changed. So why does gcc suddenly decide that it needs to re-check the value of running in this case?

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• Apache module, is it possible to have asynchronous processing

  - by prashant2361

  Hi, I have a requirement where I need to send continous updates to my clients. Client is browser in this case. We have some data which updates every sec, so once client connects to our server, we maintain a persistent connection and keep pushing data to the client. I am looking for suggestions of this implementation at the server end. Basically what I need is this: 1. client connects to server. I maintain the socket and metadata about the socket. metadata contains what updates need to be send to this client 2. server process now waits for new client connections 3. One other process will have the list of all the sockets opened and will go through each of them and send the updates if required. Can we do something like this in apache module: 1. apache process gets the new connection. It maintains the state for the connection. It keeps the state in some global memory and returns back to root process to signify that it is done so that it can accept the new connection 2. the apache process though has returned the status to root process but it is also executing parallely where it going through its global store and sending updates to the client, if any. So can a apache process do these things: 1. Have more than one connection associated with it 2. Asynchronously waiting for new connection and at the same time processing the previous connections? Regards Prashant

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• Divide and conquer of large objects for GC performance

  - by Aperion

  At my work we're discussing different approaches to cleaning up a large amount of managed ~50-100MB memory.There are two approaches on the table (read: two senior devs can't agree) and not having the experience the rest of the team is unsure of what approach is more desirable, performance or maintainability. The data being collected is many small items, ~30000 which in turn contains other items, all objects are managed. There is a lot of references between these objects including event handlers but not to outside objects. We'll call this large group of objects and references as a single entity called a blob. Approach #1: Make sure all references to objects in the blob are severed and let the GC handle the blob and all the connections. Approach #2: Implement IDisposable on these objects then call dispose on these objects and set references to Nothing and remove handlers. The theory behind the second approach is since the large longer lived objects take longer to cleanup in the GC. So, by cutting the large objects into smaller bite size morsels the garbage collector will processes them faster, thus a performance gain. So I think the basic question is this: Does breaking apart large groups of interconnected objects optimize data for garbage collection or is better to keep them together and rely on the garbage collection algorithms to processes the data for you? I feel this is a case of pre-optimization, but I do not know enough of the GC to know what does help or hinder it.

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• Read from one large file and write to many (tens, hundreds, or thousands) files in Java?

  - by Rudiger

  I have a large-ish file (4-5 GB compressed) of small messages that I wish to parse into approximately 6,000 files by message type. Messages are small; anywhere from 5 to 50 bytes depending on the type. Each message starts with a fixed-size type field (a 6-byte key). If I read a message of type '000001', I want to write append its payload to 000001.dat, etc. The input file contains a mixture of messages; I want N homogeneous output files, where each output file contains only the messages of a given type. What's an efficient a fast way of writing these messages to so many individual files? I'd like to use as much memory and processing power to get it done as fast as possible. I can write compressed or uncompressed files to the disk. I'm thinking of using a hashmap with a message type key and an outputstream value, but I'm sure there's a better way to do it. Thanks!

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• NSDictionary, NSArray, NSSet and efficiency

  - by ryyst

  Hi, I've got a text file, with about 200,000 lines. Each line represents an object with multiple properties. I only search through one of the properties (the unique ID) of the objects. If the unique ID I'm looking for is the same as the current object's unique ID, I'm gonna read the rest of the object's values. Right now, each time I search for an object, I just read the whole text file line by line, create an object for each line and see if it's the object I'm looking for - which is basically the most inefficient way to do the search. I would like to read all those objects into memory, so I can later search through them more efficiently. The question is, what's the most efficient way to perform such a search? Is a 200,000-entries NSArray a good way to do this (I doubt it)? How about an NSSet? With an NSSet, is it possible to only search for one property of the objects? Thanks for any help! -- Ry

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• Java application design question

  - by ring bearer

  I have a hobby project, which is basically to maintain 'todo' tasks in the way I like. One task can be described as: public class TodoItem { private String subject; private Date dueBy; private Date startBy; private Priority priority; private String category; private Status status; private String notes; } As you can imagine I would have 1000s of todo items at a given time. What is the best strategy to store a todo item? (currently on an XML file) such that all the items are loaded quickly up on app start up(the application shows kind of a dashboard of all the items at start up)? What is the best way to design its back-end so that it can be ported to Android/or a J2ME based phone? Currently this is done using Java Swing. What should I concentrate on so that it works efficiently on a device where memory is limited? The application throws open a form to enter new todo task. For now, I would like to save the newly added task to my-todos.xml once the user presses "save" button. What are the common ways to append such a change to an existing XML file?(note that I don't want to read the whole file again and then persist)

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