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• Approach for caching data from data logger

  - by filip-fku

  Greetings, I've been working on a C#.NET app that interacts with a data logger. The user can query and obtain logs for a specified time period, and view plots of the data. Typically a new data log is created every minute and stores a measurement for a few parameters. To get meaningful information out of the logger, a reasonable number of logs need to be acquired - data for at least a few days. The hardware interface is a UART to USB module on the device, which restricts transfers to a maximum of about 30 logs/second. This becomes quite slow when reading in the data acquired over a number of days/weeks. What I would like to do is improve the perceived performance for the user. I realize that with the hardware speed limitation the user will have to wait for the full download cycle at least the first time they acquire a larger set of data. My goal is to cache all data seen by the app, so that it can be obtained faster if ever requested again. The approach I have been considering is to use a light database, like SqlServerCe, that can store the data logs as they are received. I am then hoping to first search the cache prior to querying a device for logs. The cache would be updated with any logs obtained by the request that were not already cached. Finally my question - would you consider this to be a good approach? Are there any better alternatives you can think of? I've tried to search SO and Google for reinforcement of the idea, but I mostly run into discussions of web request/content caching. Thanks for any feedback!

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• C: Fifo between threads, writing and reading strings

  - by Yonatan

  Hello once more dear internet, I writing a small program that among other things, writes a log file of commands received. to do that, I want to use a thread that all it should do is just attempt to read from a pipe, while the main thread will write into that pipe whenever it should. Since i don't know the length of each string command, i thought about writing and reading the pointer to the char buf[MAX_MESSAGE_LEN]. Since what i've tried so far doesn't work, i'll post my best effort :P char str[] = "hello log thread 123456789 10 11 12 13 14 15 16 17 18 19\n"; if (pipe(pipe_fd) != 0) return -1; pthread_t log_thread; pthread_create(&log_thread,NULL, log_thread_start, argv[2]); success_write = 0; do { write(pipe_fd[1],(void*)&str,sizeof(char*)); } while (success_write < sizeof(char*)); and the thread does this: char buffer[MAX_MSGLEN]; int success_read; success_read = 0; //while(1) { do { success_read += read(pipe_fd[0],(void*)&buffer, sizeof(char*)); } while (success_read < sizeof(char*)); //} printf("%s",buffer); (Sorry if this doesn't indent, i can't seem to figure out this editor...) oh, and pipe_fd[2] is a global parameter. So, any help with this, either by the way i thought of, or another way i could read strings without knowing the length, would be much appreciated. On a side note, i'm working on Eclipse IDE C/C++, version 1.2.1 and i can't seem to set up the compiler so it will link the pthread library to my project. I've resorted to writing my own Makefile to make it (pun intended :P) work. Anyone knows what to do ? i've looked online, but all i find are solutions that are probably good on an older version because the tabs and option keys are different. Anyways, Thanks a bunch internet ! Yonatan

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• Java: fastest way to do random reads on huge disk file(s)

  - by cocotwo

  I've got a moderately big set of data, about 800 MB or so, that is basically some big precomputed table that I need to speed some computation by several orders of magnitude (creating that file took several mutlicores computers days to produce using an optimized and multi-threaded algo... I do really need that file). Now that it has been computed once, that 800MB of data is read only. I cannot hold it in memory. As of now it is one big huge 800MB file but splitting in into smaller files ain't a problem if it can help. I need to read about 32 bits of data here and there in that file a lot of time. I don't know before hand where I'll need to read these data: the reads are uniformly distributed. What would be the fastest way in Java to do my random reads in such a file or files? Ideally I should be doing these reads from several unrelated threads (but I could queue the reads in a single thread if needed). Is Java NIO the way to go? I'm not familiar with 'memory mapped file': I think I don't want to map the 800 MB in memory. All I want is the fastest random reads I can get to access these 800MB of disk-based data. btw in case people wonder this is not at all the same as the question I asked not long ago: http://stackoverflow.com/questions/2346722/java-fast-disk-based-hash-set

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• jQuery: If user clicks out of div

  - by Paul Knopf

  I am creating a popup in query. All is well with the popup on hover. I made it see a timer starts when user's mouse leaves the div to close it. If he enters the div again before the timer is done, then the timer is cleared. This is fine, but what if a user clicks out of the div? I want that to also close the div. The only problem is that I don't want to attach click events to the wrapper on the page (because it includes the popout menu). I have seen techniques that wraps entire screen with a transparent div, and then attach a click event to hit. Although this may work, it confuses the user if he clicks the hidden div intending to click a link. He will have to click the link twice. Once two close the div (hiding the link), and another time to actually click think. Also, you loose in mouse cursors attached to any masked elements on the page (such as links cursor pointer, etc). There has to be a way to check if the user clicked out of the div without a modal and without attaching events to the entire page (page wrappers and child elements included). onclicksomewhereelse="closeme();" lol.

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• Prob comparing pointers and integer in C

  - by Dimitri

  Hi I have a problem with this code. When i am using this function I have no warnings. : void handler(int sig){ switch(sig) { case SIGINT : { click++; fprintf(stdout,"SIGINT recu\n"); if( click == N){ exit(0); } } case SIGALRM : fprintf(stdout,"SIGALRM received\n"); exit(0); case SIGTERM: fprintf(stdout,"SIGTERM received\n"); exit(0); } } But when i rewrite the function with this new version, I have a " comparison between pointer and integer" warning on the if statement: void handler( int sig){ printf("Signal recu\n"); if( signal == SIGINT){ click++; fprintf(stdout,"SIGINT received; Click = %d\n",click); if(click == N){ fprintf(stdout,"Exiting with SIGINT\n"); exit(0); } } else if(signal == SIGALRM){ fprintf(stdout,"SIGALRM received\n"); exit(0); } else if(signal == SIGTERM){ fprintf(stdout,"SIGTERM received\n"); exit(0); } Can someone tell me where is the prob?

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• SWIG_NewPointerObj and values always being nil

  - by Tom J Nowell

  I'm using SWIG to wrap C++ objects for use in lua, and Im trying to pass data to a method in my lua script, but it always comes out as 'nil' void CTestAI::UnitCreated(IUnit* unit){ lua_getglobal(L, "ai"); lua_getfield(L, -1, "UnitCreated"); swig_module_info *module = SWIG_GetModule( L ); swig_type_info *type = SWIG_TypeQueryModule( module, module, "IUnit *" ); SWIG_NewPointerObj(L,unit,type,0); lua_epcall(L, 1, 0); } Here is the lua code: function AI:UnitCreated(unit) if(unit == nil) then game:SendToConsole("I CAN HAS nil ?") else game:SendToConsole("I CAN HAS UNITS!!!?") end end unit is always nil. I have checked and in the C++ code, the unit pointer is never invalid/null I've also tried: void CTestAI::UnitCreated(IUnit* unit){ lua_getglobal(L, "ai"); lua_getfield(L, -1, "UnitCreated"); SWIG_NewPointerObj(L,unit,SWIGTYPE_p_IUnit,0); lua_epcall(L, 1, 0); } with identical results. Why is this failing? How do I fix it?

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• Mouse management in JavaScript games

  - by Jakob

  Im using JavaScript, the HTML5 canvas-element and WebGL to make a simple 3D-game in first person view for fun. Ideally, I would like to control my movement by using the keyboard to move and the mouse to look around, like you usually do in FPS-games. As you probably understand, there are some limits to this in the browser, since the mouse cant be captured: When using the onmousemove event, no further movement will be detected when the mouse pointer reaches the border of my screen (which means that I wont be able to run in a circle for example) Seeing the mouse move across the screen is not the end of the world, but it is a little annoying From what I know, it's impossible to hide the mouse as well as setting it's position in JavaScript. Hence, my question is this: If we cant to those things, what can we do in order to get close to the desktop gaming experience when it comes to the mouse in the browser? And I mean right now, using current APIs. Not "what could be changed in some standard to make life easier". Also, I realize that I could use the keyboard to look around, but then we're back in 1995 when Quake were actually played like that. And of course I know that it would be easier to write a desktop application or use Flash at least, but Im trying to push JavaScript's limits here. Apart from those things, what are your suggestions? Any kind of reference, existing game, crazy idea, hack or even browser specific solution would be appreciated.

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• close file with fopen() but file still in use

  - by Marco

  Hi all, I've got a problem with deleting/overwriting a file using my program which is also being used(read) by my program. The problem seems to be that because of the fact my program is reading data from the file (output.txt) it puts the file in a 'in use' state which makes it impossible to delete or overwrite the file. I don't understand why the file stays 'in use' because I close the file after use with fclose(); this is my code: bool bBool = true while(bBool){ //Run myprogram.exe tot generate (a new) output.txt //Create file pointer and open file FILE* pInputFile = NULL; pInputFile = fopen("output.txt", "r"); // //then I do some reading using fscanf() // //And when I'm done reading I close the file using fclose() fclose(pInputFile); //The next step is deleting the output.txt if( remove( "output.txt" ) == -1 ){ //ERROR }else{ //Succesfull } } I use fclose() to close the file but the file remains in use by my program until my program is totally shut down. What is the solution to free the file so it can be deleted/overwrited? In reality my code isn't a loop without an end ; ) Thanks in advance! Marco

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• Efficient update of SQLite table with many records

  - by blackrim

  I am trying to use sqlite (sqlite3) for a project to store hundreds of thousands of records (would like sqlite so users of the program don't have to run a [my]sql server). I have to update hundreds of thousands of records sometimes to enter left right values (they are hierarchical), but have found the standard update table set left_value = 4, right_value = 5 where id = 12340; to be very slow. I have tried surrounding every thousand or so with begin; .... update... update table set left_value = 4, right_value = 5 where id = 12340; update... .... commit; but again, very slow. Odd, because when I populate it with a few hundred thousand (with inserts), it finishes in seconds. I am currently trying to test the speed in python (the slowness is at the command line and python) before I move it to the C++ implementation, but right now this is way to slow and I need to find a new solution unless I am doing something wrong. Thoughts? (would take open source alternative to SQLite that is portable as well)

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• Is there a recommended way to communicate scientific/engineering programming to C developers?

  - by ggkmath

  Hi, I have a lot of MATLAB code that needs to get ported to C (execution speed is critical for this work) as part of a back-end process for a web application. When I attempt to outsource this code to a C developer, I assume (correct me if I'm wrong) few C developers also understand MATLAB code (things like indexing and memory management are different, etc.). I wonder if there are any C developers out there that can recommend a procedure for me to follow to best communicate what the code does? For example, should I provide the MATLAB code and explain what it's doing line by line? Or, should I just provide the math/algorithm, explain it in plain English, and let the C developer implement it with this understanding in his/her own way (e.g. can I assume the developer understands how to work with complex math (i.e. imaginary numbers), how to generate histograms, perform an FFT, etc.)? Or, is there a better method? I expect I'm not the first to need to do this, so I wonder if any C developers out there ran into this situation and can share any conventional wisdom how they'd like this task to be transferred? Thanks in advance for any comments.

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• Flexslider links not opening

  - by Marina Nelson

  I am trying to get the slides to link to other pages on the site. The pointer shows when I click on the slides, but page does not open: <div class="flexslider"> <ul class="slides"> <li> <a href="page1.html"><img src="img/slide-1.jpg" alt="" ></a> </li> <li> <a href="page2.html"><img src="img/slide-2.jpg" alt="" ></a> </li> <li> <a href="page3.html"><img src="img/slide-3.jpg" alt="" ></a> </li> <li> <a href="page4.html"><img src="img/slide-4.jpg" alt="" ></a> </li> <li> <a href="page5.html"><img src="img/slide-5.jpg" alt="" ></a> </li> </ul> </div> I have not altered any other code. Am I missing something? I don't know Jquery well. Thanks.

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• A public struct inside a class

  - by Koning Baard

  I am new to C++, and let's say I have two classes: Creature and Human: /* creature.h */ class Creature { private: public: struct emotion { /* All emotions are percentages */ char joy; char trust; char fear; char surprise; char sadness; char disgust; char anger; char anticipation; char love; }; }; /* human.h */ class Human : Creature { }; And I have this in my main function in main.cpp: Human foo; My question is: how can I set foo's emotions? I tried this: foo->emotion.fear = 5; But GCC gives me this compile error: error: base operand of '-' has non-pointer type 'Human' This: foo.emotion.fear = 5; Gives: error: 'struct Creature::emotion' is inaccessible error: within this context error: invalid use of 'struct Creature::emotion' Can anyone help me? Thanks P.S. No I did not forget the #includes

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• Using static variables for Strings

  - by Vivart

  below content is taken from Best practice: Writing efficient code but i didn't understand why private static String x = "example"; faster than private static final String x ="example"; Can anybody explain this. Using static variables for Strings When you define static fields (also called class fields) of type String, you can increase application speed by using static variables (not final) instead of constants (final). The opposite is true for primitive data types, such as int. For example, you might create a String object as follows: private static final String x = "example"; For this static constant (denoted by the final keyword), each time that you use the constant, a temporary String instance is created. The compiler eliminates "x" and replaces it with the string "example" in the bytecode, so that the BlackBerry® Java® Virtual Machine performs a hash table lookup each time that you reference "x". In contrast, for a static variable (no final keyword), the String is created once. The BlackBerry JVM performs the hash table lookup only when it initializes "x", so access is faster. private static String x = "example"; You can use public constants (that is, final fields), but you must mark variables as private.

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• Better language or checking tool?

  - by rwallace

  This is primarily aimed at programmers who use unmanaged languages like C and C++ in preference to managed languages, forgoing some forms of error checking to obtain benefits like the ability to work in extremely resource constrained systems or the last increment of performance, though I would also be interested in answers from those who use managed languages. Which of the following would be of most value? A language that would optionally compile to CLR byte code or to machine code via C, and would provide things like optional array bounds checking, more support for memory management in environments where you can't use garbage collection, and faster compile times than typical C++ projects. (Think e.g. Ada or Eiffel with Python syntax.) A tool that would take existing C code and perform static analysis to look for things like potential null pointer dereferences and array overflows. (Think e.g. an open source equivalent to Coverity.) Something else I haven't thought of. Or put another way, when you're using C family languages, is the top of your wish list more expressiveness, better error checking or something else? The reason I'm asking is that I have a design and prototype parser for #1, and an outline design for #2, and I'm wondering which would be the better use of resources to work on after my current project is up and running; but I think the answers may be useful for other tools programmers also. (As usual with questions of this nature, if the answer you would give is already there, please upvote it.)

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• im i doing this right or wrong using pointers in C

  - by Amandeep Singh Dhari

  i like to point out that i need some help with my home work, ok the lectuer gave us the idea of a program and we have to make it from bottom to top. got to have user to type in two set of string. pointers take in the value and then puts into a prototype i need to make a 3rd pointer that has the value of p1 and p2. like this p1 = asd, p2 = qwe and p3 = asdqwe #include "stdafx.h" #include <ctype.h> char *mystrcat(char*s1p, char*s2p); // Prototype char main(void) { char string1[80]; char string2[80]; printf("%s", "enter in your srting one "); gets_s(string1); printf("%s", "enter in your srting two "); gets_s(string2); *mystrcat(string1, string2); return 0; } char *mystrcat(char *s1p,char *s2p) { //char *string3; //char *string4; //string3 = s1p; //string4 = s2p; printf("whatever = %s%s\n", s1p, s2p); return 0; } this is the code that i made so far just need some help, thank guys in advance.

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• read files from directory and filter files from Java

  - by Adnan

  The following codes goes through all directories and sub-directories and outputs just .java files; import java.io.File; public class DirectoryReader { private static String extension = "none"; private static String fileName; public static void main(String[] args ){ String dir = "C:/tmp"; File aFile = new File(dir); ReadDirectory(aFile); } private static void ReadDirectory(File aFile) { File[] listOfFiles = aFile.listFiles(); if (aFile.isDirectory()) { listOfFiles = aFile.listFiles(); if(listOfFiles!=null) { for(int i=0; i < listOfFiles.length; i++ ) { if (listOfFiles[i].isFile()) { fileName = listOfFiles[i].toString(); int dotPos = fileName.lastIndexOf("."); if (dotPos > 0) { extension = fileName.substring(dotPos); } if (extension.equals(".java")) { System.out.println("FILE:" + listOfFiles[i] ); } } if(listOfFiles[i].isDirectory()) { ReadDirectory(listOfFiles[i]); } } } } } } Is this efficient? What could be done to increase the speed? All ideas are welcome.

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• HREF link that targets nothing, does not want to use hash or void(0)

  - by Mattis

  I have a link that I want to be able to click to trigger a piece of jQuery code. Currently I have <a href="#" id="foo">Link</a> and $('#foo').click(function(){ // Do stuff }); which works well. But, I have always hated using hash in this way. The page flickers and the hash is added to the page url. One alternative is to use <a href="javascript:void(0);" id="foo">Link</a> but I also dislike seeing that piece of code in the browser status bar. It looks tacky. What I'd rather have is an explanatory javascript placeholder that does nothing, like <a href="javascript:zoom();" id="foo">Link</a> which actually works, but throws an ReferenceError in the javascript console since there are no such function. What's the minimum definition of a function that does nothing? Are there any other alternatives? Should I just skip the link and use something like <span id="foo" style="cursor:pointer;cursor:hand;">Link</span> instead?

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• Guidance required: FIrst time gonna work with real high end database (size = 50GB).

  - by claws

  I got a project of designing a Database. This is going to be my first big scale project. Good thing about it is information is mostly organized & currently stored in text files. The size of this information is 50GB. There are going to be few millions of records in each Table. Its going to have around 50 tables. I need to provide a web interface for searching & browsing. I'm going to use MySQL DBMS. I've never worked with a database more than 200MB before. So, speed & performance was never a concern but I followed things like normalization & Indexes. I never used any kind of testing/benchmarking/queryOptimization/whatever because I never had to care about them. But here the purpose of creating a database is to make it quickly searchable. So, I need to consider all possible aspects in design. I was browsing archives & found: http://stackoverflow.com/questions/1981526/what-should-every-developer-know-about-databases http://stackoverflow.com/questions/621884/database-development-mistakes-made-by-app-developers I'm gonna keep the points mentioned in above answers in mind. What else should I know? What else should I keep in mind?

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• Issue selenium code maintenance

  - by Rajasankar

  I want to group the common methods in one file and use it. For example, login to a page using selenium may be used in multiple times. Define that in class A and call it in class B. However, it throws null pointer exception. class A has public void test_Login() throws Exception { try{ selenium.setTimeout("60000"); selenium.open("http://localhost"); selenium.windowFocus(); selenium.windowMaximize(); selenium.windowFocus(); selenium.type("userName", "admin"); selenium.type("password", "admin"); Result=selenium.isElementPresent("//input[@type='image']"); selenium.click("//input[@type='image']"); selenium.waitForPageToLoad(Timeout); } catch(Exception ex) { System.out.println(ex); ex.printStackTrace(); } } with all other java syntax in class B public void test_kk() throws Exception { try { a.test_Login(); } catch(Exception ex) { System.out.println(ex); ex.printStackTrace(); } } with all syntax. When I execute class B, I got this error, java.lang.NullPointerException at A.test_Login(A.java:32) at B.test_kk(savefile.java:58) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at junit.framework.TestCase.runTest(TestCase.java:168) at junit.framework.TestCase.runBare(TestCase.java:134) at com.thoughtworks.selenium.SeleneseTestCase.runBare(SeleneseTestCase.j ava:212) at junit.framework.TestResult$1.protect(TestResult.java:110) at junit.framework.TestResult.runProtected(TestResult.java:128) at junit.framework.TestResult.run(TestResult.java:113) at junit.framework.TestCase.run(TestCase.java:124) at junit.framework.TestSuite.runTest(TestSuite.java:232) at junit.framework.TestSuite.run(TestSuite.java:227) at junit.textui.TestRunner.doRun(TestRunner.java:116) at junit.textui.TestRunner.doRun(TestRunner.java:109) at junit.textui.TestRunner.run(TestRunner.java:77) at B.main(B.java:77) I hope someone must have tried this before. I may miss something here.

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• Looking for a good C++/.net

  - by Michael Minerva

  I have recently started to feel that I need to greatly improve my C++ skills especially in the realm of .net. I graduated from a good four year university with a degree in computer science about 9 months ago and I have since been doing full time contract work for a small software company in my local area. Most of my work has been done using Java/lisp/cocoa/XML and before that most of my programming in my senior year was in java/C#. I did a decent amount of C++ in my Sophomore year and in my free time before that but I feel that my general knowledge of C++/.net is very lacking for the opportunities that are now coming my way. Can anyone recommend a good book that could help me get up too speed? I feel I do not need a very basic introduction to C++ but something that covers the fundamentals of .net would be good for me. So basically what I need is a book or books that would be good for a .net novice and a C++ developer who is just beyond novice. Also, a book that would help bein an interview by giving me a conversional understanding of C++ would be great. Thanks a lot!.

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• Msysgit bash is horrendously slow in Windows 7

  - by Kevin L.

  I love git and use it on OS X pretty much constantly at home. At work, we use svn on Windows, but want to migrate to git as soon as the tools have fully matured (not just TortoiseGit, but also something akin the really nice Visual Studio integration provided by VisualSVN). But I digress... I recently installed msysgit on my Windows 7 machine, and when using the included version of bash, it is horrendously slow. And not just the git operations; clear takes about five seconds. AAAAH! Has anyone experienced a similar issue? Edit: It appears that msysgit is not playing nicely with UAC and might just be a tiny design oversight resulting from developing on XP or running Vista or 7 with UAC disabled; starting Git Bash using Run as administrator results in the lightning speed I see with OS X (or on 7 after starting Git Bash w/o a network connection - see @Gauthier answer). Edit 2: AH HA! See my answer.

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• JavaScript: List global variables in IE

  - by Quandary

  I'm trying to get the instance name of my class. The way I do this is I loop through all global objects and compare it with the this pointer. It works in Chrome and FF, but in IE, it doesn't. The problem seems to be the global variables don't seem to be in window. How can I loop through the global variables in IE ? PS: I know it only works as long as there is only one instance, and I don't want to pass the instance's name as a parameter. function myClass() { this.myName = function () { // search through the global object for a name that resolves to this object for (var name in this.global) { if (this.global[name] == this) return name } } } function myClass_chrome() { this.myName = function () { // search through the global object for a name that resolves to this object for (var name in window) { if (window[name] == this) return name ; } } ; } // store the global object, which can be referred to as this at the top level, in a // property on our prototype, so we can refer to it in our object's methods myClass.prototype.global = this //myClass_IE.prototype.global = this // create a global variable referring to an object // var myVar = new myClass() var myVar = new myClass_chrome() //var myVar = new myClass_IE() alert(myVar.myName() );// returns "myVar"

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• How to optimize paging for large in memory database

  - by snakefoot

  I have an application where the entire database is implemented in memory using a stl-map for each table in the database. Each item in the stl-map is a complex object with references to other items in the other stl-maps. The application works with a large amount of data, so it uses more than 500 MByte RAM. Clients are able to contact the application and get a filtered version of the entire database. This is done by running through the entire database, and finding items relevant for the client. When the application have been running for an hour or so, then Windows 2003 SP2 starts to page out parts of the RAM for the application (Eventhough there is 16 GByte RAM on the machine). After the application have been partly paged out then a client logon takes a long time (10 mins) because it now generates a page fault for each pointer lookup in the stl-map. I can see it is possible to tell Windows to lock memory in RAM, but this is generally only recommended for device drivers, and only for "small" amounts of memory. I guess a poor mans solution could be to loop through the entire memory database, and thus tell Windows we are still interested in keeping the datamodel in RAM. I guess another poor mans solution could be to disable the pagefile completely on Windows. I guess the expensive solution would be a SQL database, and then rewrite the entire application to use a database layer. Then hopefully the database system will have implemented means to for fast access. Are there other more elegant solutions ?

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• Advice: Python Framework Server/Worker Queue management (not Website)

  - by Muppet Geoff

  I am looking for some advice/opinions of which Python Framework to use in an implementation of multiple 'Worker' PCs co-ordinated from a central Queue Manager. For completeness, the 'Worker' PCs will be running Audio Conversion routines (which I do not need advice on, and have standalone code that works). The Audio conversion takes a long time, and I need to co-ordinate an arbitrary number of the 'Workers' from a central location, handing them conversion tasks (such as where to get the source files, or where to ask for the job configuration) with them reporting back some additional info, such as the runtime of the converted audio etc. At present, I have a script that makes a webservice call to get the 'configuration' for a conversion task, based on source files located on the worker already (we manually copy the source files to the worker, and that triggers a conversion routine). I want to change this, so that we can distribute conversion tasks ("Oy you, process this: xxx") based on availability, and in an ideal world, based on pending tasks too. There is a chance that Workers can go offline mid-conversion (but this is not likely). All the workers are Windows based, the co-ordinator can be WIndows or Linux. I have (in my initial searches) come across the following - and I know that some are cross-dependent: Celery (with RabbitMQ) Twisted Django Using a framework, rather than home-brewing, seems to make more sense to me right now. I have a limited timeframe in which to develop this functional extension. An additional consideration would be using a Framework that is compatible with PyQT/PySide so that I can write a simple UI to display Queue status etc. I appreciate that the specifics above are a little vague, and I hope that someone can offer me a pointer or two. Again: I am looking for general advice on which Python framework to investigate further, for developing a Server/Worker 'Queue management' solution, for non-web activities (this is why DJango didn't seem the right fit).

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• I need a fast runtime expression parser

  - by Chris Lively

  I need to locate a fast, lightweight expression parser. Ideally I want to pass it a list of name/value pairs (e.g. variables) and a string containing the expression to evaluate. All I need back from it is a true/false value. The types of expressions should be along the lines of: varA == "xyz" and varB==123 Basically, just a simple logic engine whose expression is provided at runtime. UPDATE At minimum it needs to support ==, !=, , =, <, <= Regarding speed, I expect roughly 5 expressions to be executed per request. We'll see somewhere in the vicinity of 100/requests a second. Our current pages tend to execute in under 50ms. Usually there will only be 2 or 3 variables involved in any expression. However, I'll need to load approximately 30 into the parser prior to execution. UPDATE 2012/11/5 Update about performance. We implemented nCalc nearly 2 years ago. Since then we've expanded it's use such that we average 40+ expressions covering 300+ variables on post backs. There are now thousands of post backs occurring per second with absolutely zero performance degradation. We've also extended it to include a handful of additional functions, again with no performance loss. In short, nCalc met all of our needs and exceeded our expectations.

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