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  • g++ SSE intrinsics dilemma - value from intrinsic "saturates"

    - by Sriram
    Hi, I wrote a simple program to implement SSE intrinsics for computing the inner product of two large (100000 or more elements) vectors. The program compares the execution time for both, inner product computed the conventional way and using intrinsics. Everything works out fine, until I insert (just for the fun of it) an inner loop before the statement that computes the inner product. Before I go further, here is the code: //this is a sample Intrinsics program to compute inner product of two vectors and compare Intrinsics with traditional method of doing things. #include <iostream> #include <iomanip> #include <xmmintrin.h> #include <stdio.h> #include <time.h> #include <stdlib.h> using namespace std; typedef float v4sf __attribute__ ((vector_size(16))); double innerProduct(float* arr1, int len1, float* arr2, int len2) { //assume len1 = len2. float result = 0.0; for(int i = 0; i < len1; i++) { for(int j = 0; j < len1; j++) { result += (arr1[i] * arr2[i]); } } //float y = 1.23e+09; //cout << "y = " << y << endl; return result; } double sse_v4sf_innerProduct(float* arr1, int len1, float* arr2, int len2) { //assume that len1 = len2. if(len1 != len2) { cout << "Lengths not equal." << endl; exit(1); } /*steps: * 1. load a long-type (4 float) into a v4sf type data from both arrays. * 2. multiply the two. * 3. multiply the same and store result. * 4. add this to previous results. */ v4sf arr1Data, arr2Data, prevSums, multVal, xyz; //__builtin_ia32_xorps(prevSums, prevSums); //making it equal zero. //can explicitly load 0 into prevSums using loadps or storeps (Check). float temp[4] = {0.0, 0.0, 0.0, 0.0}; prevSums = __builtin_ia32_loadups(temp); float result = 0.0; for(int i = 0; i < (len1 - 3); i += 4) { for(int j = 0; j < len1; j++) { arr1Data = __builtin_ia32_loadups(&arr1[i]); arr2Data = __builtin_ia32_loadups(&arr2[i]); //store the contents of two arrays. multVal = __builtin_ia32_mulps(arr1Data, arr2Data); //multiply. xyz = __builtin_ia32_addps(multVal, prevSums); prevSums = xyz; } } //prevSums will hold the sums of 4 32-bit floating point values taken at a time. Individual entries in prevSums also need to be added. __builtin_ia32_storeups(temp, prevSums); //store prevSums into temp. cout << "Values of temp:" << endl; for(int i = 0; i < 4; i++) cout << temp[i] << endl; result += temp[0] + temp[1] + temp[2] + temp[3]; return result; } int main() { clock_t begin, end; int length = 100000; float *arr1, *arr2; double result_Conventional, result_Intrinsic; // printStats("Allocating memory."); arr1 = new float[length]; arr2 = new float[length]; // printStats("End allocation."); srand(time(NULL)); //init random seed. // printStats("Initializing array1 and array2"); begin = clock(); for(int i = 0; i < length; i++) { // for(int j = 0; j < length; j++) { // arr1[i] = rand() % 10 + 1; arr1[i] = 2.5; // arr2[i] = rand() % 10 - 1; arr2[i] = 2.5; // } } end = clock(); cout << "Time to initialize array1 and array2 = " << ((double) (end - begin)) / CLOCKS_PER_SEC << endl; // printStats("Finished initialization."); // printStats("Begin inner product conventionally."); begin = clock(); result_Conventional = innerProduct(arr1, length, arr2, length); end = clock(); cout << "Time to compute inner product conventionally = " << ((double) (end - begin)) / CLOCKS_PER_SEC << endl; // printStats("End inner product conventionally."); // printStats("Begin inner product using Intrinsics."); begin = clock(); result_Intrinsic = sse_v4sf_innerProduct(arr1, length, arr2, length); end = clock(); cout << "Time to compute inner product with intrinsics = " << ((double) (end - begin)) / CLOCKS_PER_SEC << endl; //printStats("End inner product using Intrinsics."); cout << "Results: " << endl; cout << " result_Conventional = " << result_Conventional << endl; cout << " result_Intrinsics = " << result_Intrinsic << endl; return 0; } I use the following g++ invocation to build this: g++ -W -Wall -O2 -pedantic -march=i386 -msse intrinsics_SSE_innerProduct.C -o innerProduct Each of the loops above, in both the functions, runs a total of N^2 times. However, given that arr1 and arr2 (the two floating point vectors) are loaded with a value 2.5, the length of the array is 100,000, the result in both cases should be 6.25e+10. The results I get are: Results: result_Conventional = 6.25e+10 result_Intrinsics = 5.36871e+08 This is not all. It seems that the value returned from the function that uses intrinsics "saturates" at the value above. I tried putting other values for the elements of the array and different sizes too. But it seems that any value above 1.0 for the array contents and any size above 1000 meets with the same value we see above. Initially, I thought it might be because all operations within SSE are in floating point, but floating point should be able to store a number that is of the order of e+08. I am trying to see where I could be going wrong but cannot seem to figure it out. I am using g++ version: g++ (GCC) 4.4.1 20090725 (Red Hat 4.4.1-2). Any help on this is most welcome. Thanks, Sriram.

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  • How does a historical debugger work?

    - by mafutrct
    A historical debugger is able to revert program state (including current instruction) to a former state. How is this possible in managed or unmanaged environments? I can't imagine that the debugger takes a state shot of the whole system on every instruction.

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  • In Java What is the guaranteed way to get a FileLock from FileChannel while accessing a RandomAcces

    - by narasimha.bhat
    I am trying to use FileLock lock(long position, long size,boolean shared) in FileChannel object As per the javadoc it can throw OverlappingFileLockException. When I create a test program with 2 threads lock method seems to be waiting to acquire the lock (both exclusive and non exclusive) But when the number threads increases in the acutal scenario over lapping file lock exception is thrown and processing slows down due the block at File lock table. What is the best way to acquire lock avoiding the OverlappingFileLockException ?

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  • Finite State Machine Spellchecker

    - by Durell
    I would love to have a debugged copy of the finite state machine code below. I tried debugging but could not, all the machine has to do is to spell check the word "and",an equivalent program using case is welcomed. #include<cstdlib> #include<stdio.h> #include<string.h> #include<iostream> #include<string> using namespace std; char in_str; int n; void spell_check() { char data[256]; int i; FILE *in_file; in_file=fopen("C:\\Users\\mytorinna\\Desktop\\a.txt","r+"); while (!feof(in_file)) { for(i=0;i<256;i++) { fscanf(in_file,"%c",in_str); data[i]=in_str; } //n = strlen(in_str); //start(data); cout<<data; } } void start(char data) { // char next_char; //int i = 0; // for(i=0;i<256;i++) // if (n == 0) { if(data[i]="a") { state_A(); exit; } else { cout<<"I am comming"; } // cout<<"This is an empty string"; // exit();//do something here to terminate the program } } void state_A(int i) { if(in_str[i] == 'n') { i++; if(i<n) state_AN(i); else error(); } else error(); } void state_AN(int i) { if(in_str[i] == 'd') { if(i == n-1) cout<<" Your keyword spelling is correct"; else cout<<"Wrong keyword spelling"; } } int main() { spell_check(); system("pause"); return 0; }

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  • snmp, how to retrieve ip connected to the router with MIB-II

    - by dany
    Hi all, I want to create a program that acts as manager and that queries the router (or sets a trap) to obtain the list of ip connected to it. My router has these functionalities: SNMP v1, v2c, built-in MIB-I, MIB-II agent. Is it possible to retrieve these informations quering the MIB-II agent of the router in a standard way (not vendor dependent)? Bye

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  • gtk2 auto translation is choosing the wrong language

    - by Andrew Heath
    Not sure if yall can help this time, as I'm just using this particular program not coding with it... I downloaded Deluge, a free torrent app, and it requires GTK2 Runtime which I've also installed. Unfortunately, on my English WinXP with East Asian Language support Deluge sets itself to Chinese menus and has no option to alter the language. A bit of poking around on the internet suggests this is due to GTK2 selecting the wrong default language. Does anyone know how I can override this?

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  • Execute a Application On The Server Using PHP

    - by Nathan Campos
    I have an application on my server that is called leaf.exe, that haves two arguments needed to run, they are: inputfile and outputfile, that will be like this example: pnote.exe input.pnt output.txt The executable is at exec/, inputfile is at upload/ and outputfile is on compiled/. But I need that a PHP could run the application like that, then I want to know: How could I do this? How could I echo the output of the program?

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  • How does assembly language interact with something like the Internet?

    - by Maulrus
    So I was thinking about languages the other day, and it struck me that any program written in a compiled language that interacts with the Internet is then translated into assembly that has to interact with the Internet. I've just begun learning a bit of x86 assembly to help me understand C++ a bit better, and I'm baffled by how something so low-level could do something like access the Internet. I'm sure the full answer to this question is much more than would fit in a SO answer, but could somebody give me maybe a basic summary?

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  • Most complicated C code to read

    - by cprogrammer
    ITT: Post a program that doesn't do anything, but breaks all syntax highlighting. ??=include<stdio.h> // lol????/ why does this compile???????/ haha :> int main()<%int lol<:0x1UL??);printf("%.""0s",(0[lol]??'=*lol,&lol<:(unsigned)"hi"??)));??>

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  • Robust and easy to implement serial bus (automotive application)

    - by JcMaco
    What serial communication bus would you use in a automotive embedded system if your main selection criteria were: * Electrically robust * Slow speed (32 kb/s) * Easy to program * Easy to interface with microcontrollers It won't be transferring much data, but it will need to be transferred periodically at high speed (100 - 500 Hz). I find that RS-232 is just not reliable enough if you have noise in your ground line. CAN-bus seems interesting, but I have no experience with it. We are currently interested in a combination of AVR AT90CAN128 microcontrollers.

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  • Visual Studio soft-crashing when encountering XAML Errors in initialize.

    - by Aren
    I've been having some serious issues with Visual Studio 2010 as of late. It's been crashing in a peculiar way when I encounter certain types of XAML errors during the InitializeComponent() of a control/window. The program breaks and visual studio gears up like it's catching an exception (because it is) and then stops midway displaying a broken highlight in my XAML file with no details as to what is wrong. Example: There is not pop outs, or details Anywhere about what is wrong, only a callstack that points to my InitializeComponent() call. Now normally I'd just do some trial and error to fix this problem, and find out where i messed up, but the real problem isn't my code. Visual Studio is rendered completely useless at this point. It reports my application still in "Running" mode. The Stop/Break/Restart buttons on the toolbar or in the menus don't do anything (but grey out). Closing the application does not stop this behaviour, closing visual studio gets it stuck in a massive loop where it yells at me complaining every file open is not in the debug project, then repeats this process when i have exausted every open file. I have to force-close devenv.exe, and after this happening 3-4 times in a row it's a lot of wasted time (as my projects are usually pretty big and studio can be quite slow @ loading). To the point Has anyone else experienced this? How can I stop studio from locking up. Can I at LEAST get information out of this beast another way so i can fix my XAML error sooner rather than after 3-4 trial-and-error compiles yielding the same crash? Any & All help would be appreciated. Visual Studio 2010 version: 10.0.30319.1RTM Edit & Update FWIW, mostly the errors that cause this are XamlParseExceptions (I figured this out after i found what was wrong with my XAML). I think I need to be clearer though, Im not looking for the solution to my code problem, as these are usually typos / small things, I'm looking for a solution to VStudio getting all buggered up as a result. The particular error in the above image that 100% for sure caused this was a XamlParseException caused by forgetting a Value attribute on a data trigger. I've fixed that part but it still doesn't tell my why my studio becomes a lump of neutered program when a perfectly normal exception is thrown in the parsing of the XAML. Code that will cause this issue (at least for me) This is the base template WPF Application, with the following Window.xaml code. The problem is a missing Value="True" on the <DataTrigger ...> in the template. It generates a XamlParseException and Visual Studio Crashes as described above when debugging it. Final Notes The following solutions did not help me: Restarting Visual Studio Rebooting Reinstalling Visual Studio

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  • ASP.NET reading files from BIN

    - by nettguy
    I am processing some CSV file which i have copied in Bin folder of My ASP.NET Website. When i execute using (IDataReader csv = new CsvReader (new StreamReader("sample.txt"), true, '|')) { ..... } it complains me that "sample.txt" not found in "c:\Program Files\.....\" Won't the runtime automatically look into the bin folder? what modification do i need to do?

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  • getting started with Google Closure if you don't care about minifying/compiling?

    - by Tim
    If you don't care about minifying your code, is there a way to get started using the Google Closure library without having to set up a subversion client and use the compiler? The Notepad sample program on Google's website refers to <script src="closure-library/base.js" > </script > Can you simply download closure-library/base.js somewhere and start playing with the UI examples? The Closure Lite quick-start version doesn't appear to include goog.ui

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  • Where do you download a package with java.exe?

    - by Derek
    I was trying to run this java ee program with session beans which involves the 'ant' command apparently and when I try to run 'ant' it says... '"java.exe"' is not recognized as an internal or external command. Soooo I am thinking I need to get java.exe in order to use 'ant' properly. Where can I find it? What downloadable contains it?

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  • Calculating next date in Turbo Pascal

    - by Chaima Chaimouta
    program date; uses wincrt; var m,ch,ch1,ch2,ch3: string ; mois,j,a,b: integer ; begin write('a');read(a); write('j');read(j); write('mois');read(mois); case mois of 1,3,5,7,8,10: if j<31 then begin b:=j+1; m:=str(b,ch)+'/'+str(mois,ch2)+'/'+str(a,ch3); else if j=31then b:=1; s:=mois+1; m:=concat(str(b,ch),'/',str(s,ch2),'/',str(a,ch3)); end else m:='erreur'; 4,6,9,11:if j<30 then begin b:=j+1; m:=concat(str(b,ch),'/',str(mois,ch2),'/',str(a,ch3)); end else j=30 then begin b:=1; s:=mois+1; m:=concat(str(b,ch),'/',str(mois,ch2),'/',str(a,ch3)); end else m:='erreur'; 2:if j<28 then begin b:=j+1; m:=concat(str(b,ch),'/',str(mois,ch2),'/',str(a,ch3)); end else if j=28 then begin b:=1; m:=concat(str(b,ch),'/',str(mois,ch2,'/',str(a,ch3)); end else if((a mod 4=0)AND (a mod 100<>0)) or ((a mod 100=0)and(a mod 400=0)) then if j<29 then begin b:=j+1; m:=concat(str(b,ch),'/',str(mois,ch2,'/',str(a,ch3)); end else if j=29 then begin b:=1; m:=concat(str(b,ch),'/',str(mois,ch2,'/',str(a,ch3)); end else m:='erreur'; 12:if j<31 then begin b:=j+1; m:=concat(str(b,ch),'/',str(mois,ch2,'/',str(a,ch3)); end else if j=31 then begin b:=1; s:=a+1; m:=concat(str(b,ch),'/',str(mois,ch2,'/',str(s,ch3)); end; writeln(m); end. this is my program i hope you be able to help me

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  • How to check Linux version with Autoconf?

    - by Goofy
    My program requires at least Linux 2.6.26 (I use timerfd and some other Linux-specific features). I have an general idea how to write this macro but I don't have enough knowledge about writing test macros for Autoconf. Algorithm: Run "uname --release" and store output Parse output and subtract Linux version number (MAJOR.MINOR.MICRO) Compare version I don't know how to run command, store output and parse it. Maybe such macro already exists and it's available (I haven't found any)?

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  • Removing file locks in Windows and Java

    - by Jack
    I have a Java program that opens a file using the RandomAccessFile class. I'd like to be able to rename that file while it is opened by Java. In Unix, this isn't a problem. Does anyone know how I can do this in Windows? Should I set Java to open it a certain way? Thanks in advance.

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  • If I write an algorithm to encrypt a file, are their tools available to break the encryption?

    - by Andrew
    I have an idea for encryption that I could program fairly easily to encrypt some local text file. Given that my approach is novel, and does not use any of the industry standard encryption techniques, would I be able to test the strength of my encryption using 'cracker' apps or suchlike? Or do all those tools rely on advanced knowledge of the encryption process (or intercepted 'keys'), meaning I'd have to build my own cracker for testing?

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