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  • How to use a divider in a navigation with list elements?

    - by Kris
    I want to create a navigation which got divider between each list element. Here is a simple HTML/CSS Code/Template : <nav> <ul> <li><a href="#">A</a></li> <li><a href="#">B</a></li> <li><a href="#">C</a></li> <li><a href="#">D</a></li> <li><a href="#">E</a></li> </ul> </nav> nav ul { list-style:none; float:right; } nav ul li { float:left; padding-left:10px; } nav ul li a { color:#111; font-family:Verdana; font-size:15px; text-decoration:none; } nav ul li a:hover { color:#9F3039; } so just a simple looking navigation which floats from the right side on a logo which is not displayed in the code here. Now I want to at devider between each link - I know I could do it with border-right and just use another class on my last listelement which set the border-right off, BUT I want to use a special kind of divider - an image. How can I do it best ?

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  • Why doesn't my <div> float around another floated <div> while other elements do?

    - by user1848605
    I have a container with background color green. Inside that green <div>, I have a <div> which is black and styled as a box (50px x 50px) - this <div> is floated to the left. Now if I add a <p> to my markup after the grey <div>, I'd expect it to float around the grey <div>. And it does. However, when I substitue with another <div> which is styled as box (set height and width), it doesn't float around anymore, but disappears behind the floating div. Even if I have first paragraphs which are floating around correctly and THEN I add the div (box), the paragraphs stop floating around and appear on another line. HTML: <div id="greencontainer"> <div id="blackbox"></div> <!--this one is float:left;--> <p>A paragraph that floats around the previous div</p> <div id="anotherbox"></div> <!-- if I add another div with set width and height, it disappears behind the floated one, and even prevents the paragraph from floating around.--> </div> CSS: #blackbox { width:50px; height:50px; background-color:black; float:left; } #p { margin:0px; padding:0px; } #anotherbox { width:50px; height:50px; background-color:grey; }

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  • I can't seem to figure out type variables mixed with classes.

    - by onmach
    I pretty much understand 3/4 the rest of the language, but every time I dip my feet into using classes in a meaningful way in my code I get permantently entrenched. Why doesn't this extremely simple code work? data Room n = Room n n deriving Show class HasArea a where width :: (Num n) => a -> n instance (Num n) => HasArea (Room n) where width (Room w h) = w So, room width is denoted by ints or maybe floats, I don't want to restrict it at this point. Both the class and the instance restrict the n type to Nums, but it still doesn't like it and I get this error: Couldn't match expected type `n1' against inferred type `n' `n1' is a rigid type variable bound by the type signature for `width' at Dungeon.hs:11:16 `n' is a rigid type variable bound by the instance declaration at Dungeon.hs:13:14 In the expression: w In the definition of `width': width (Room w h) = w In the instance declaration for `HasArea (Room n)' So it tells me the types doesn't match, but it doesn't tell me what types it thinks they are, which would be really helpful. As a side note, is there any easy way to debug an error like this? The only way I know to do it is to randomly change stuff until it works.

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  • How can I speed-up this loop (in C)?

    - by splicer
    Hi! I'm trying to parallelize a convolution function in C. Here's the original function which convolves two arrays of 64-bit floats: void convolve(const Float64 *in1, UInt32 in1Len, const Float64 *in2, UInt32 in2Len, Float64 *results) { UInt32 i, j; for (i = 0; i < in1Len; i++) { for (j = 0; j < in2Len; j++) { results[i+j] += in1[i] * in2[j]; } } } In order to allow for concurrency (without semaphores), I created a function that computes the result for a particular position in the results array: void convolveHelper(const Float64 *in1, UInt32 in1Len, const Float64 *in2, UInt32 in2Len, Float64 *result, UInt32 outPosition) { UInt32 i, j; for (i = 0; i < in1Len; i++) { if (i > outPosition) break; j = outPosition - i; if (j >= in2Len) continue; *result += in1[i] * in2[j]; } } The problem is, using convolveHelper slows down the code about 3.5 times (when running on a single thread). Any ideas on how I can speed-up convolveHelper, while maintaining thread safety?

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  • Assigning a 2D array (of pointers) to a variable in an object for access in C++?

    - by MrMormon
    I'm sorry if I didn't pick a descriptive or concise name. A lot of questions sound similar, but I haven't been able to find what I'm looking for. What I want to do is store a 2D array of pointers somewhere and assign a variable in some object to that array to be able to access it. Here's some example code that has the same compile error I'm getting with a bigger project. #include <iostream> using namespace std; struct X{ float * b[8][8]; X(){ *(b[1][5]) = 1; cout << *(b[1][5]) << endl; } void Set(float * c[8][8]){ b = c; cout << *(b[1][5]) << endl; } }; main(){ float * a[8][8]; *(a[1][5]) = 2; X obj; obj.Set(a); } What I want to happen in this code is that an X object starts with its own 2D array, whose value pointed to by b[1][5] should be printed as "1". Then the main method's 2D array, a, is passed to the object's Set() method and assigned to its array variable. The value pointed to by b[1][5] should then be printed as "2". However, I can't figure out what type the Set() parameter, c, should be. I get error: incompatible types in assignment of ‘float* (*)[8]’ to ‘float* [8][8]’ when I try to compile. As for why I want to do this, I'm trying to use an array of pointers to objects, not floats, but it's the same error.

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  • 11415 compile errors FTW?!

    - by Koning Baard
    Hello. This is something I've really never seen but, I downloaded the source code of the sine wave example at http://www.audiosynth.com/sinewavedemo.html . It is in an old Project Builder Project format, and I want to compile it with Xcode (GCC). However, Xcode gives me 11415 compile errors. The first few are (all in the precompilation of AppKit.h): /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:31:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:31: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:33:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:33: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:35:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:35: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:36:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:36: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:37:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:37: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:38:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:38: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:40:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:40: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:42:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:42: error: expected identifier or '(' before '@' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:48:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:48: error: expected identifier or '(' before '@' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:54:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:54: error: expected identifier or '(' before '@' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:59:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:59: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:61:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:61: error: expected identifier or '(' before '@' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:69:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:69: error: expected identifier or '(' before '+' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:71:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:71: error: expected identifier or '(' before '+' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:39:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:39: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:40:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:40: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:41:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:41: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:42:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:42: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:43:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:43: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:44:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:44: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:45:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:45: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:46:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:46: error: expected identifier or '(' before '-' token Some of the code is: HAL.c /* * HAL.c * Sinewave * * Created by james on Fri Apr 27 2001. * Copyright (c) 2001 __CompanyName__. All rights reserved. * */ #include "HAL.h" #include "math.h" appGlobals gAppGlobals; OSStatus appIOProc (AudioDeviceID inDevice, const AudioTimeStamp* inNow, const AudioBufferList* inInputData, const AudioTimeStamp* inInputTime, AudioBufferList* outOutputData, const AudioTimeStamp* inOutputTime, void* device); #define FailIf(cond, handler) \ if (cond) { \ goto handler; \ } #define FailWithAction(cond, action, handler) \ if (cond) { \ { action; } \ goto handler; \ } // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ // HAL Sample Code ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ //#define noErr 0 //#define false 0 OSStatus SetupHAL (appGlobalsPtr globals) { OSStatus err = noErr; UInt32 count, bufferSize; AudioDeviceID device = kAudioDeviceUnknown; AudioStreamBasicDescription format; // get the default output device for the HAL count = sizeof(globals->device); // it is required to pass the size of the data to be returned err = AudioHardwareGetProperty(kAudioHardwarePropertyDefaultOutputDevice, &count, (void *) &device); fprintf(stderr, "kAudioHardwarePropertyDefaultOutputDevice %d\n", err); if (err != noErr) goto Bail; // get the buffersize that the default device uses for IO count = sizeof(globals->deviceBufferSize); // it is required to pass the size of the data to be returned err = AudioDeviceGetProperty(device, 0, false, kAudioDevicePropertyBufferSize, &count, &bufferSize); fprintf(stderr, "kAudioDevicePropertyBufferSize %d %d\n", err, bufferSize); if (err != noErr) goto Bail; // get a description of the data format used by the default device count = sizeof(globals->deviceFormat); // it is required to pass the size of the data to be returned err = AudioDeviceGetProperty(device, 0, false, kAudioDevicePropertyStreamFormat, &count, &format); fprintf(stderr, "kAudioDevicePropertyStreamFormat %d\n", err); fprintf(stderr, "sampleRate %g\n", format.mSampleRate); fprintf(stderr, "mFormatFlags %08X\n", format.mFormatFlags); fprintf(stderr, "mBytesPerPacket %d\n", format.mBytesPerPacket); fprintf(stderr, "mFramesPerPacket %d\n", format.mFramesPerPacket); fprintf(stderr, "mChannelsPerFrame %d\n", format.mChannelsPerFrame); fprintf(stderr, "mBytesPerFrame %d\n", format.mBytesPerFrame); fprintf(stderr, "mBitsPerChannel %d\n", format.mBitsPerChannel); if (err != kAudioHardwareNoError) goto Bail; FailWithAction(format.mFormatID != kAudioFormatLinearPCM, err = paramErr, Bail); // bail if the format is not linear pcm // everything is ok so fill in these globals globals->device = device; globals->deviceBufferSize = bufferSize; globals->deviceFormat = format; Bail: return (err); } /* struct AudioStreamBasicDescription { Float64 mSampleRate; // the native sample rate of the audio stream UInt32 mFormatID; // the specific encoding type of audio stream UInt32 mFormatFlags; // flags specific to each format UInt32 mBytesPerPacket; // the number of bytes in a packet UInt32 mFramesPerPacket; // the number of frames in each packet UInt32 mBytesPerFrame; // the number of bytes in a frame UInt32 mChannelsPerFrame; // the number of channels in each frame UInt32 mBitsPerChannel; // the number of bits in each channel }; typedef struct AudioStreamBasicDescription AudioStreamBasicDescription; */ // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ // This is a simple playThru ioProc. It simply places the data in the input buffer back into the output buffer. // Watch out for feedback from Speakers to Microphone OSStatus appIOProc (AudioDeviceID inDevice, const AudioTimeStamp* inNow, const AudioBufferList* inInputData, const AudioTimeStamp* inInputTime, AudioBufferList* outOutputData, const AudioTimeStamp* inOutputTime, void* appGlobals) { appGlobalsPtr globals = appGlobals; int i; double phase = gAppGlobals.phase; double amp = gAppGlobals.amp; double pan = gAppGlobals.pan; double freq = gAppGlobals.freq * 2. * 3.14159265359 / globals->deviceFormat.mSampleRate; int numSamples = globals->deviceBufferSize / globals->deviceFormat.mBytesPerFrame; // assume floats for now.... float *out = outOutputData->mBuffers[0].mData; for (i=0; i<numSamples; ++i) { float wave = sin(phase) * amp; phase = phase + freq; *out++ = wave * (1.0-pan); *out++ = wave * pan; } gAppGlobals.phase = phase; return (kAudioHardwareNoError); } // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ OSStatus StartPlayingThruHAL(appGlobalsPtr globals) { OSStatus err = kAudioHardwareNoError; if (globals->soundPlaying) return 0; globals->phase = 0.0; err = AudioDeviceAddIOProc(globals->device, appIOProc, (void *) globals); // setup our device with an IO proc if (err != kAudioHardwareNoError) goto Bail; err = AudioDeviceStart(globals->device, appIOProc); // start playing sound through the device if (err != kAudioHardwareNoError) goto Bail; globals->soundPlaying = true; // set the playing status global to true Bail: return (err); } // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ OSStatus StopPlayingThruHAL(appGlobalsPtr globals) { OSStatus err = kAudioHardwareNoError; if (!globals->soundPlaying) return 0; err = AudioDeviceStop(globals->device, appIOProc); // stop playing sound through the device if (err != kAudioHardwareNoError) goto Bail; err = AudioDeviceRemoveIOProc(globals->device, appIOProc); // remove the IO proc from the device if (err != kAudioHardwareNoError) goto Bail; globals->soundPlaying = false; // set the playing status global to false Bail: return (err); } Sinewave.m // // a very simple Cocoa CoreAudio app // by James McCartney [email protected] www.audiosynth.com // // Sinewave - this class implements a sine oscillator with dezippered control of frequency, pan and amplitude // #import "Sinewave.h" // define a C struct from the Obj-C object so audio callback can access data typedef struct { @defs(Sinewave); } sinewavedef; // this is the audio processing callback. OSStatus appIOProc (AudioDeviceID inDevice, const AudioTimeStamp* inNow, const AudioBufferList* inInputData, const AudioTimeStamp* inInputTime, AudioBufferList* outOutputData, const AudioTimeStamp* inOutputTime, void* defptr) { sinewavedef* def = defptr; // get access to Sinewave's data int i; // load instance vars into registers double phase = def->phase; double amp = def->amp; double pan = def->pan; double freq = def->freq; double ampz = def->ampz; double panz = def->panz; double freqz = def->freqz; int numSamples = def->deviceBufferSize / def->deviceFormat.mBytesPerFrame; // assume floats for now.... float *out = outOutputData->mBuffers[0].mData; for (i=0; i<numSamples; ++i) { float wave = sin(phase) * ampz; // generate sine wave phase = phase + freqz; // increment phase // write output *out++ = wave * (1.0-panz); // left channel *out++ = wave * panz; // right channel // de-zipper controls panz = 0.001 * pan + 0.999 * panz; ampz = 0.001 * amp + 0.999 * ampz; freqz = 0.001 * freq + 0.999 * freqz; } // save registers back to object def->phase = phase; def->freqz = freqz; def->ampz = ampz; def->panz = panz; return kAudioHardwareNoError; } @implementation Sinewave - (void) setup { OSStatus err = kAudioHardwareNoError; UInt32 count; device = kAudioDeviceUnknown; initialized = NO; // get the default output device for the HAL count = sizeof(device); // it is required to pass the size of the data to be returned err = AudioHardwareGetProperty(kAudioHardwarePropertyDefaultOutputDevice, &count, (void *) &device); if (err != kAudioHardwareNoError) { fprintf(stderr, "get kAudioHardwarePropertyDefaultOutputDevice error %ld\n", err); return; } // get the buffersize that the default device uses for IO count = sizeof(deviceBufferSize); // it is required to pass the size of the data to be returned err = AudioDeviceGetProperty(device, 0, false, kAudioDevicePropertyBufferSize, &count, &deviceBufferSize); if (err != kAudioHardwareNoError) { fprintf(stderr, "get kAudioDevicePropertyBufferSize error %ld\n", err); return; } fprintf(stderr, "deviceBufferSize = %ld\n", deviceBufferSize); // get a description of the data format used by the default device count = sizeof(deviceFormat); // it is required to pass the size of the data to be returned err = AudioDeviceGetProperty(device, 0, false, kAudioDevicePropertyStreamFormat, &count, &deviceFormat); if (err != kAudioHardwareNoError) { fprintf(stderr, "get kAudioDevicePropertyStreamFormat error %ld\n", err); return; } if (deviceFormat.mFormatID != kAudioFormatLinearPCM) { fprintf(stderr, "mFormatID != kAudioFormatLinearPCM\n"); return; } if (!(deviceFormat.mFormatFlags & kLinearPCMFormatFlagIsFloat)) { fprintf(stderr, "Sorry, currently only works with float format....\n"); return; } initialized = YES; fprintf(stderr, "mSampleRate = %g\n", deviceFormat.mSampleRate); fprintf(stderr, "mFormatFlags = %08lX\n", deviceFormat.mFormatFlags); fprintf(stderr, "mBytesPerPacket = %ld\n", deviceFormat.mBytesPerPacket); fprintf(stderr, "mFramesPerPacket = %ld\n", deviceFormat.mFramesPerPacket); fprintf(stderr, "mChannelsPerFrame = %ld\n", deviceFormat.mChannelsPerFrame); fprintf(stderr, "mBytesPerFrame = %ld\n", deviceFormat.mBytesPerFrame); fprintf(stderr, "mBitsPerChannel = %ld\n", deviceFormat.mBitsPerChannel); } - (void)setAmpVal:(double)val { amp = val; } - (void)setFreqVal:(double)val { freq = val * 2. * 3.14159265359 / deviceFormat.mSampleRate; } - (void)setPanVal:(double)val { pan = val; } - (BOOL)start { OSStatus err = kAudioHardwareNoError; sinewavedef *def; if (!initialized) return false; if (soundPlaying) return false; // initialize phase and de-zipper filters. phase = 0.0; freqz = freq; ampz = amp; panz = pan; def = (sinewavedef *)self; err = AudioDeviceAddIOProc(device, appIOProc, (void *) def); // setup our device with an IO proc if (err != kAudioHardwareNoError) return false; err = AudioDeviceStart(device, appIOProc); // start playing sound through the device if (err != kAudioHardwareNoError) return false; soundPlaying = true; // set the playing status global to true return true; } - (BOOL)stop { OSStatus err = kAudioHardwareNoError; if (!initialized) return false; if (!soundPlaying) return false; err = AudioDeviceStop(device, appIOProc); // stop playing sound through the device if (err != kAudioHardwareNoError) return false; err = AudioDeviceRemoveIOProc(device, appIOProc); // remove the IO proc from the device if (err != kAudioHardwareNoError) return false; soundPlaying = false; // set the playing status global to false return true; } @end Can anyone help me compiling this example? I'd really appriciate it. Thanks

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  • Why would GLCapabilities.setHardwareAccelerated(true/false) have no effect on performance?

    - by Luke
    I've got a JOGL application in which I am rendering 1 million textures (all the same texture) and 1 million lines between those textures. Basically it's a ball-and-stick graph. I am storing the vertices in a vertex array on the card and referencing them via index arrays, which are also stored on the card. Each pass through the draw loop I am basically doing this: gl.glBindBuffer(GL.GL_ARRAY_BUFFER, <buffer id>); gl.glBindBuffer(GL.GL_ELEMENT_ARRAY_BUFFER, <buffer id>); gl.glDrawElements(GL.GL_POINTS, <size>, GL.GL_UNSIGNED_INT, 0); gl.glBindBuffer(GL.GL_ARRAY_BUFFER, <buffer id>); gl.glBindBuffer(GL.GL_ELEMENT_ARRAY_BUFFER, <buffer id>); gl.glDrawElements(GL.GL_LINES, <size>, GL.GL_UNSIGNED_INT, 0); I noticed that the JOGL library is pegging one of my CPU cores. Every frame, the run method internal to the library is taking quite long. I'm not sure why this is happening since I have called setHardwareAccelerated(true) on the GLCapabilities used to create my canvas. What's more interesting is that I changed it to setHardwareAccelerated(false) and there was no impact on the performance at all. Is it possible that my code is not using hardware rendering even when it is set to true? Is there any way to check? EDIT: As suggested, I have tested breaking my calls up into smaller chunks. I have tried using glDrawRangeElements and respecting the limits that it requests. All of these simply resulted in the same pegged CPU usage and worse framerates. I have also narrowed the problem down to a simpler example where I just render 4 million textures (no lines). The draw loop then just doing this: gl.glEnableClientState(GL.GL_VERTEX_ARRAY); gl.glEnableClientState(GL.GL_INDEX_ARRAY); gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT); gl.glMatrixMode(GL.GL_MODELVIEW); gl.glLoadIdentity(); <... Camera and transform related code ...> gl.glEnableVertexAttribArray(0); gl.glEnable(GL.GL_TEXTURE_2D); gl.glAlphaFunc(GL.GL_GREATER, ALPHA_TEST_LIMIT); gl.glEnable(GL.GL_ALPHA_TEST); <... Bind texture ...> gl.glBindBuffer(GL.GL_ARRAY_BUFFER, <buffer id>); gl.glBindBuffer(GL.GL_ELEMENT_ARRAY_BUFFER, <buffer id>); gl.glDrawElements(GL.GL_POINTS, <size>, GL.GL_UNSIGNED_INT, 0); gl.glDisable(GL.GL_TEXTURE_2D); gl.glDisable(GL.GL_ALPHA_TEST); gl.glDisableVertexAttribArray(0); gl.glFlush(); Where the first buffer contains 12 million floats (the x,y,z coords of the 4 million textures) and the second (element) buffer contains 4 million integers. In this simple example it is simply the integers 0 through 3999999. I really want to know what is being done in software that is pegging my CPU, and how I can make it stop (if I can). My buffers are generated by the following code: gl.glBindBuffer(GL.GL_ARRAY_BUFFER, <buffer id>); gl.glBufferData(GL.GL_ARRAY_BUFFER, <size> * BufferUtil.SIZEOF_FLOAT, <buffer>, GL.GL_STATIC_DRAW); gl.glVertexAttribPointer(0, 3, GL.GL_FLOAT, false, 0, 0); and: gl.glBindBuffer(GL.GL_ELEMENT_ARRAY_BUFFER, <buffer id>); gl.glBufferData(GL.GL_ELEMENT_ARRAY_BUFFER, <size> * BufferUtil.SIZEOF_INT, <buffer>, GL.GL_STATIC_DRAW); ADDITIONAL INFO: Here is my initialization code: gl.setSwapInterval(1); //Also tried 0 gl.glShadeModel(GL.GL_SMOOTH); gl.glClearDepth(1.0f); gl.glEnable(GL.GL_DEPTH_TEST); gl.glDepthFunc(GL.GL_LESS); gl.glHint(GL.GL_PERSPECTIVE_CORRECTION_HINT, GL.GL_FASTEST); gl.glPointParameterfv(GL.GL_POINT_DISTANCE_ATTENUATION, POINT_DISTANCE_ATTENUATION, 0); gl.glPointParameterfv(GL.GL_POINT_SIZE_MIN, MIN_POINT_SIZE, 0); gl.glPointParameterfv(GL.GL_POINT_SIZE_MAX, MAX_POINT_SIZE, 0); gl.glPointSize(POINT_SIZE); gl.glTexEnvf(GL.GL_POINT_SPRITE, GL.GL_COORD_REPLACE, GL.GL_TRUE); gl.glEnable(GL.GL_POINT_SPRITE); gl.glClearColor(clearColor.getX(), clearColor.getY(), clearColor.getZ(), 0.0f); Also, I'm not sure if this helps or not, but when I drag the entire graph off the screen, the FPS shoots back up and the CPU usage falls to 0%. This seems obvious and intuitive to me, but I thought that might give a hint to someone else.

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  • IsNumeric() Broken? Only up to a point.

    - by Phil Factor
    In SQL Server, probably the best-known 'broken' function is poor ISNUMERIC() . The documentation says 'ISNUMERIC returns 1 when the input expression evaluates to a valid numeric data type; otherwise it returns 0. ISNUMERIC returns 1 for some characters that are not numbers, such as plus (+), minus (-), and valid currency symbols such as the dollar sign ($).'Although it will take numeric data types (No, I don't understand why either), its main use is supposed to be to test strings to make sure that you can convert them to whatever numeric datatype you are using (int, numeric, bigint, money, smallint, smallmoney, tinyint, float, decimal, or real). It wouldn't actually be of much use anyway, since each datatype has different rules. You actually need a RegEx to do a reasonably safe check. The other snag is that the IsNumeric() function  is a bit broken. SELECT ISNUMERIC(',')This cheerfully returns 1, since it believes that a comma is a currency symbol (not a thousands-separator) and you meant to say 0, in this strange currency.  However, SELECT ISNUMERIC(N'£')isn't recognized as currency.  '+' and  '-' is seen to be numeric, which is stretching it a bit. You'll see that what it allows isn't really broken except that it doesn't recognize Unicode currency symbols: It just tells you that one numeric type is likely to accept the string if you do an explicit conversion to it using the string. Both these work fine, so poor IsNumeric has to follow suit. SELECT  CAST('0E0' AS FLOAT)SELECT  CAST (',' AS MONEY) but it is harder to predict which data type will accept a '+' sign. SELECT  CAST ('+' AS money) --0.00SELECT  CAST ('+' AS INT)   --0SELECT  CAST ('+' AS numeric)/* Msg 8115, Level 16, State 6, Line 4 Arithmetic overflow error converting varchar to data type numeric.*/SELECT  CAST ('+' AS FLOAT)/*Msg 8114, Level 16, State 5, Line 5Error converting data type varchar to float.*/> So we can begin to say that the maybe IsNumeric isn't really broken, but is answering a silly question 'Is there some numeric datatype to which i can convert this string? Almost, but not quite. The bug is that it doesn't understand Unicode currency characters such as the euro or franc which are actually valid when used in the CAST function. (perhaps they're delaying fixing the euro bug just in case it isn't necessary).SELECT ISNUMERIC (N'?23.67') --0SELECT  CAST (N'?23.67' AS money) --23.67SELECT ISNUMERIC (N'£100.20') --1SELECT  CAST (N'£100.20' AS money) --100.20 Also the CAST function itself is quirky in that it cannot convert perfectly reasonable string-representations of integers into integersSELECT ISNUMERIC('200,000')       --1SELECT  CAST ('200,000' AS INT)   --0/*Msg 245, Level 16, State 1, Line 2Conversion failed when converting the varchar value '200,000' to data type int.*/  A more sensible question is 'Is this an integer or decimal number'. This cuts out a lot of the apparent quirkiness. We do this by the '+E0' trick. If we want to include floats in the check, we'll need to make it a bit more complicated. Here is a small test-rig. SELECT  PossibleNumber,         ISNUMERIC(CAST(PossibleNumber AS NVARCHAR(20)) + 'E+00') AS Hack,        ISNUMERIC (PossibleNumber + CASE WHEN PossibleNumber LIKE '%E%'                                          THEN '' ELSE 'E+00' END) AS Hackier,        ISNUMERIC(PossibleNumber) AS RawIsNumericFROM    (SELECT CAST(',' AS NVARCHAR(10)) AS PossibleNumber          UNION SELECT '£' UNION SELECT '.'         UNION SELECT '56' UNION SELECT '456.67890'         UNION SELECT '0E0' UNION SELECT '-'         UNION SELECT '-' UNION SELECT '.'         UNION  SELECT N'?' UNION SELECT N'¢'        UNION  SELECT N'?' UNION SELECT N'?34.56'         UNION SELECT '-345' UNION SELECT '3.332228E+09') AS examples Which gives the result ... PossibleNumber Hack Hackier RawIsNumeric-------------- ----------- ----------- ------------? 0 0 0- 0 0 1, 0 0 1. 0 0 1¢ 0 0 1£ 0 0 1? 0 0 0?34.56 0 0 00E0 0 1 13.332228E+09 0 1 1-345 1 1 1456.67890 1 1 156 1 1 1 I suspect that this is as far as you'll get before you abandon IsNumeric in favour of a regex. You can only get part of the way with the LIKE wildcards, because you cannot specify quantifiers. You'll need full-blown Regex strings like these ..[-+]?\b[0-9]+(\.[0-9]+)?\b #INT or REAL[-+]?\b[0-9]{1,3}\b #TINYINT[-+]?\b[0-9]{1,5}\b #SMALLINT.. but you'll get even these to fail to catch numbers out of range.So is IsNumeric() an out and out rogue function? Not really, I'd say, but then it would need a damned good lawyer.

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  • Fluid CSS: floating column with max-width and overflow

    - by Ates Goral
    I'm using a fluid layout in the new theme that I'm working on for my blog. I often blog about code and include <pre> blocks within the posts. The float: left column for the content area has a max-width so that the column stops at a certain maximum width and can also be shrunk: +----------+ +------+ | text | | text | | | | | | | | | | | | | | | | | | | | | +----------+ +------+ max shrunk What I want is for the <pre> elements to be wider than the text column so that I can fit 80-character-wrapped code without horizontal scroll bars. But I want the <pre> elements to overflow from the content area, without affecting its fluidity: +----------+ +------+ | text | | text | | | | | +----------+--+ +------+------+ | code | | code | +----------+--+ +------+------+ | | | | +----------+ +------+ max shrunk But, max-width stops being fluid once I insert the overhanging <pre> in there: the width of the column remains at the specified max-width even when I shrink the browser beyond that width. I've reproduced the issue with this bare-minimum scenario: <div style="float: left; max-width: 460px; border: 1px solid red"> <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit</p> <pre style="max-width: 700px; border: 1px solid blue"> function foo() { // Lorem ipsum dolor sit amet, consectetur adipisicing elit } </pre> <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit</p> </div> I noticed that doing either of the following brings back the fluidity: Remove the <pre> (doh...) Remove the float: left The workaround I'm currently using is to insert the <pre> elements into "breaks" in the post column, so that the widths of the post segments and the <pre> segments are managed mutually exclusively: +----------+ +------+ | text | | text | +----------+ +------+ +-------------+ +-------------+ | code | | code | +-------------+ +-------------+ +----------+ +------+ +----------+ +------+ max shrunk But this forces me to insert additional closing and opening <div> elements into the post markup which I'd rather keep semantically pristine. Admittedly, I don't have a full grasp of how the box model works with floats with overflowing content, so I don't understand why the combination of float: left on the container and the <pre> inside it cripple the max-width of the container. I'm observing the same problem on Firefox/Chrome/Safari/Opera. IE6 (the crazy one) seems happy all the time. This also doesn't seem dependent on quirks/standards mode. Update I've done further testing to observe that max-width seems to get ignored when the element has a float: left. I glanced at the W3C box model chapter but couldn't immediately see an explicit mention of this behaviour. Any pointers?

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  • Need help receiving ByteArray data

    - by k80sg
    Hi folks, I am trying to receive byte array data from a machine. It sends out 3 different types of data structure each with different number of fields which consist of mostly int and a few floats, and byte sizes, the first being 320 bytes, 420 for the second type and 560 for the third. When the sending program is launched, it fires all 3 types of data simultaneouly with an interval of 1 sec. Example: Sending order: Pack1 - 320 bytes 1 sec later Pack2 - 420 bytes 1 sec later Pack3 - 560 bytes 1 sec later Pack1 - 320 bytes ... .. . How do I check the incoming byte size before passing it to: byte[] handsize = new byte[bytesize]; as the data I receive are all out of order, for instance using the following the read all int: System.out.println("Reading data in int format:" + " " + datainput.readInt()); I get many different sets of values whenever I run my prog although with some valid field data but they are all over the place. I am not too sure how exactly should I do it but I tried the following and apparently my data fields are not receiving in correct sequence: BufferedInputStream bais = new BufferedInputStream(requestSocket.getInputStream()); DataInputStream datainput = new DataInputStream(bais); byte[] handsize = new byte[560]; datainput.readFully(handsize); int n = 0; int intByte[] = new int[140]; for (int i = 0; i < 140 ; i++) { System.out.println("Reading data in int format:" + " " + datainput.readInt()); intByte[n] = datainput.readInt(); n = n + 1; System.out.println("The value in array is:" + intByte[0]); System.out.println("The value in array is:" + intByte[1]); System.out.println("The value in array is:" + intByte[2]); System.out.println("The value in array is:" + intByte[3]); Also from the above code, the order of the values printed out with System.out.println("Reading data in int format:" + " " + datainput.readInt()); and System.out.println("The value in array is:" + intByte[0]); System.out.println("The value in array is:" + intByte[1]); are different. Any help will be appreciated. Thanks

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  • Need help programming with Mclauren series and Taylor series!

    - by user352258
    Ok so here's what i have so far: #include <stdio.h> #include <math.h> //#define PI 3.14159 int factorial(int n){ if(n <= 1) return(1); else return(n * factorial(n-1)); } void McLaurin(float pi){ int factorial(int); float x = 42*pi/180; int i, val=0, sign; for(i=1, sign=-1; i<11; i+=2){ sign *= -1; // alternate sign of cos(0) which is 1 val += (sign*(pow(x, i)) / factorial(i)); } printf("\nMcLaurin of 42 = %d\n", val); } void Taylor(float pi){ int factorial(int); float x; int i; float val=0.00, sign; float a = pi/3; printf("Enter x in degrees:\n"); scanf("%f", &x); x=x*pi/180.0; printf("%f",x); for(i=0, sign=-1.0; i<2; i++){ if(i%2==1) sign *= -1.0; // alternate sign of cos(0) which is 1 printf("%f",sign); if(i%2==1) val += (sign*sin(a)*(pow(x-a, i)) / factorial(i)); else val += (sign*cos(a)*(pow(x-a, i)) / factorial(i)); printf("%d",factorial(i)); } printf("\nTaylor of sin(%g degrees) = %d\n", (x*180.0)/pi, val); } main(){ float pi=3.14159; void McLaurin(float); void Taylor(float); McLaurin(pi); Taylor(pi); } and here's the output: McLaurin of 42 = 0 Enter x in degrees: 42 0.733038-1.00000011.0000001 Taylor of sin(42 degrees) = -1073741824 I suspect the reason for these outrageous numbers goes with the fact that I mixed up my floats and ints? But i just cant figure it out...!! Maybe its a math thing, but its never been a strength of mine let alone program with calculus. Also the Mclaurin fails, how does it equal zero? WTF! Please help correct my noobish code. I am still a beginner...

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  • Learning Treetop

    - by cmartin
    I'm trying to teach myself Ruby's Treetop grammar generator. I am finding that not only is the documentation woefully sparse for the "best" one out there, but that it doesn't seem to work as intuitively as I'd hoped. On a high level, I'd really love a better tutorial than the on-site docs or the video, if there is one. On a lower level, here's a grammar I cannot get to work at all: grammar SimpleTest rule num (float / integer) end rule float ( (( '+' / '-')? plain_digits '.' plain_digits) / (( '+' / '-')? plain_digits ('E' / 'e') plain_digits ) / (( '+' / '-')? plain_digits '.') / (( '+' / '-')? '.' plain_digits) ) { def eval text_value.to_f end } end rule integer (( '+' / '-' )? plain_digits) { def eval text_value.to_i end } end rule plain_digits [0-9] [0-9]* end end When I load it and run some assertions in a very simple test object, I find: assert_equal @parser.parse('3.14').eval,3.14 Works fine, while assert_equal @parser.parse('3').eval,3 raises the error: NoMethodError: private method `eval' called for # If I reverse integer and float on the description, both integers and floats give me this error. I think this may be related to limited lookahead, but I cannot find any information in any of the docs to even cover the idea of evaluating in the "or" context A bit more info that may help. Here's pp information for both those parse() blocks. The float: SyntaxNode+Float4+Float0 offset=0, "3.14" (eval,plain_digits): SyntaxNode offset=0, "" SyntaxNode+PlainDigits0 offset=0, "3": SyntaxNode offset=0, "3" SyntaxNode offset=1, "" SyntaxNode offset=1, "." SyntaxNode+PlainDigits0 offset=2, "14": SyntaxNode offset=2, "1" SyntaxNode offset=3, "4": SyntaxNode offset=3, "4" The Integer... note that it seems to have been defined to follow the integer rule, but not caught the eval() method: SyntaxNode+Integer0 offset=0, "3" (plain_digits): SyntaxNode offset=0, "" SyntaxNode+PlainDigits0 offset=0, "3": SyntaxNode offset=0, "3" SyntaxNode offset=1, "" Update: I got my particular problem working, but I have no clue why: rule integer ( '+' / '-' )? plain_digits { def eval text_value.to_i end } end This makes no sense with the docs that are present, but just removing the extra parentheses made the match include the Integer1 class as well as Integer0. Integer1 is apparently the class holding the eval() method. I have no idea why this is the case. I'm still looking for more info about treetop.

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  • Style list of divs as 2 column layout with css

    - by Anders Svensson
    I'm trying out ASP.NET MVC 2 by going through the "NerdDinner" tutorial. But apparently version 2 of MVC doesn't create a Details page the same as in the tutorial, and you get divs with css classes on them to style. However, I want to get the style where each label is followed on the same line with the field, and I can't do it, I get them on top of each other, or if I try using floats weird things happen (probably because I don't know exactly how to use it in this situation, where every other div should be on the same line). Here's the generated html for the Details page: <fieldset> <legend>Fields</legend> <div> <div class="display-label">DinnerID</div> <div class="display-field"><%: Model.DinnerID %></div> <div class="display-label">Title</div> <div class="display-field"><%: Model.Title %></div> <div class="display-label">EventDate</div> <div class="display-field"><%: String.Format("{0:g}", Model.EventDate) %></div> <div class="display-label">Description</div> <div class="display-field"><%: Model.Description %></div> <div class="display-label">HostedBy</div> <div class="display-field"><%: Model.HostedBy %></div> <div class="display-label">ContactPhone</div> <div class="display-field"><%: Model.ContactPhone %></div> <div class="display-label">Address</div> <div class="display-field"><%: Model.Address %></div> <div class="display-label">Country</div> <div class="display-field"><%: Model.Country %></div> <div class="display-label">Latitude</div> <div class="display-field"><%: String.Format("{0:F}", Model.Latitude) %></div> <div class="display-label">Longitude</div> <div class="display-field"><%: String.Format("{0:F}", Model.Longitude) %></div> <div class="display-label">IsValid</div> <div class="display-field"><%: Model.IsValid %></div> </div> </fieldset> How do I get the display-label and display-field for each "entry" to appear on the same line?

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  • Is there any reasonable use of a function returning an anonymous struct?

    - by Akanksh
    Here is an (artificial) example of using a function that returns an anonymous struct and does "something" useful: #include <iostream> template<typename T> T* func( T* t, float a, float b ) { if(!t) { t = new T; t->a = a; t->b = b; } else { t->a += a; t->b += b; } return t; } struct { float a, b; }* foo(float a, float b) { if(a==0) return 0; return func(foo(a-1,b), a, b); } int main() { std::cout << foo(5,6)->a << std::endl; std::cout << foo(5,6)->b << std::endl; void* v = (void*)(foo(5,6)); float* f = (float*)(v); //[1] delete f now because I know struct is floats only. std::cout << f[0] << std::endl; std::cout << f[1] << std::endl; delete[] f; return 0; } There are a few points I would like to discuss: As is apparent, this code leaks, is there anyway I can NOT leak without knowing what the underlying struct definition is? see Comment [1]. I have to return a pointer to an anonymous struct so I can create an instance of the object within the templatized function func, can I do something similar without returning a pointer? I guess the most important, is there ANY (real-world) use for this at all? As the example given above leaks and is admittedly contrived. By the way, what the function foo(a,b) does is, to return a struct containing two numbers, the sum of all numbers from 1 to a and the product of a and b. EDIT: Maybe the line new T could use a boost::shared_ptr somehow to avoid leaks, but I haven't tried that. Would that work?

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  • Menu floating to the right on IE and to the left in FF

    - by the_drow
    I am working on a website that has a menu which behaves correctly on FF but not on IE (as usuall). On IE it floats to the right while it should float to the left, however if float is set to none it behaves almost correctly, attaching the onto the top of the container. Here's the css: #navigation_wrap { background: url(../images/ltr/nav_bg.png); height: 34px; width: 954px; } .btn_login { float: right; margin: 4px 4px 0 0; } .navigation { float: left; } .navigation ul { list-style: none; margin: 8px 0 0 15px; } .navigation ul li { border-right: 1px solid white; float: left; padding: 0 12px 0 12px; } .navigation ul li.last { border: none; } .navigation ul li a { color: white; font-size: 14px; text-decoration: none; } .navigation ul li a:hover { text-decoration: underline; } .navigation ul li a.active { font-weight: bold; } And here's the html: <div id="navigation_wrap"> <div class="navigation"> <ul> <li><a class="active" href="default.asp">Home Page</a></li> <li><a class="" href="faq.asp">FAQ</a></li><li><a class="" href="articles.asp">Articles</a></li> <li><a class="" href="products.asp">Packages &amp; Pricing</a></li> <li><a class="" href="gp.asp?gpid=15">test1</a></li> <li><a class=" last" href="gp.asp?gpid=17">test asher</a></li> </ul> </div> <div class="btn_login"> ... </div> </div> I hope anyone would have an idea. Thanks, Omer.

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  • How to troubleshoot a Highcharts script that's not rendering data when date is added and hanging the JS engine with large datasets?

    - by ylluminate
    I have a Highchart JS graph that I'm building in Rails (although I don't think Ruby has real bearing on this problem unless it's the Date output format) to which I'm adding the timestamp of each datapoint. Presently the array of floats is rendering fine without timestamps, however when I add the timestamp to the series it fails to rend. What's worse is that when the series has hundreds of entries all sorts of problems arise, not the least of which is the browser entirely hanging and requiring a force quit / kill. I'm using the following to build the array of arrays data series: series1 = readings.map{|row| [(row.date.to_i * 1000), (row.data1.to_f if BigDecimal(row.data1) != BigDecimal("-1000.0"))] } This yields a result like this: series: [{"name":"Data 1","data":[[1326262980000,1.79e-09],[1326262920000,1.29e-09],[1326262860000,1.22e-09],[1326262800000,1.42e-09],[1326262740000,1.29e-09],[1326262680000,1.34e-09],[1326262620000,1.31e-09],[1326262560000,1.51e-09],[1326262500000,1.24e-09],[1326262440000,1.7e-09],[1326262380000,1.24e-09],[1326262320000,1.29e-09],[1326262260000,1.53e-09],[1326262200000,1.23e-09],[1326262140000,1.21e-09]],"color":"blue"}] Yet nothing appears on the graph as noted. Notwithstanding, when I compare the data series in one of their very similar examples here: http://www.highcharts.com/demo/spline-irregular-time It appears that really the data series are formatted identically (except in mine I use the timestamp vs date method). This leads me to think I've got a problem with the timestamp output, but I'm just not able to figure out where / how as I'm converting the date output to an integer multipled by 1000 to convert it to milliseconds as per explained in a similar Railscasts tutorial. I would very much appreciate it if someone could point me in the right direction here as to what I may be doing wrong. What could cause no data to appear on the graph in smaller sized sets (<100 points) and when into the hundreds causes an apparent hang in the javascript engine in this case? Perhaps ultimately the key lies here as this is the entire js that's being generated and not rendering: jQuery(function() { // 1. Define JSON options var options = { chart: {"defaultSeriesType":"spline","renderTo":"chart_name"}, title: {"text":"Title"}, legend: {"layout":"vertical","style":{}}, xAxis: {"title":{"text":"UTC Time"},"type":"datetime"}, yAxis: [{"title":{"text":"Left Title","margin":10}},{"title":{"text":"Right Groups Title"},"opposite":true}], tooltip: {"enabled":true}, credits: {"enabled":false}, plotOptions: {"areaspline":{}}, series: [{"name":"Data 1","data":[[1326262980000,1.79e-08],[1326262920000,1.69e-08],[1326262860000,1.62e-08],[1326262800000,1.42e-08],[1326262740000,1.29e-08],[1326262680000,1.34e-08],[1326262620000,1.31e-08],[1326262560000,1.51e-08],[1326262500000,1.64e-08],[1326262440000,1.7e-08],[1326262380000,1.64e-08],[1326262320000,1.69e-08],[1326262260000,1.53e-08],[1326262200000,1.23e-08],[1326262140000,1.21e-08]],"color":"blue"},{"name":"Data 2","data":[[1326262980000,9.79e-09],[1326262920000,9.78e-09],[1326262860000,9.8e-09],[1326262800000,9.82e-09],[1326262740000,9.88e-09],[1326262680000,9.89e-09],[1326262620000,1.3e-06],[1326262560000,1.32e-06],[1326262500000,1.33e-06],[1326262440000,1.33e-06],[1326262380000,1.34e-06],[1326262320000,1.33e-06],[1326262260000,1.32e-06],[1326262200000,1.32e-06],[1326262140000,1.32e-06]],"color":"red"}], subtitle: {} }; // 2. Add callbacks (non-JSON compliant) // 3. Build the chart var chart = new Highcharts.StockChart(options); });

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  • Moving a unit precisely along a path in x,y coordinates

    - by Adam Eberbach
    I am playing around with a strategy game where squads move around a map. Each turn a certain amount of movement is allocated to a squad and if the squad has a destination the points are applied each turn until the destination is reached. Actual distance is used so if a squad moves one position in the x or y direction it uses one point, but moving diagonally takes ~1.4 points. The squad maintains actual position as float which is then rounded to allow drawing the position on the map. The path is described by touching the squad and dragging to the end position then lifting the pen or finger. (I'm doing this on an iPhone now but Android/Qt/Windows Mobile would work the same) As the pointer moves x, y points are recorded so that the squad gains a list of intermediate destinations on the way to the final destination. I'm finding that the destinations are not evenly spaced but can be further apart depending on the speed of the pointer movement. Following the path is important because obstacles or terrain matter in this game. I'm not trying to remake Flight Control but that's a similar mechanic. Here's what I've been doing, but it just seems too complicated (pseudocode): getDestination() { - self.nextDestination = remove_from_array(destinations) - self.gradient = delta y to destination / delta x to destination - self.angle = atan(self.gradient) - self.cosAngle = cos(self.angle) - self.sinAngle = sin(self.angle) } move() { - get movement allocation for this turn - if self.nextDestination not valid - - getNextDestination() - while(nextDestination valid) && (movement allocation remains) { - - find xStep and yStep using movement allocation and sinAngle/cosAngle calculated for current self.nextDestination - - if current position + xStep crosses the destination - - - find x movement remaining after self.nextDestination reached - - - calculate remaining direct path movement allocation (xStep remaining / cosAngle) - - - make self.position equal to self.nextDestination - - else - - - apply xStep and yStep to current position - } - round squad's float coordinates to integer screen coordinates - draw squad image on map } That's simplified of course, stuff like sign needs to be tweaked to ensure movement is in the right direction. If trig is the best way to do it then lookup tables can be used or maybe it doesn't matter on modern devices like it used to. Suggestions for a better way to do it? an update - iPhone has zero issues with trig and tracking tens of positions and tracks implemented as described above and it draws in floats anyway. The Bresenham method is more efficient, trig is more precise. If I was to use integer Bresenham I would want to multiply by ten or so to maintain a little more positional accuracy to benefit collisions/terrain detection.

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  • segmented reduction with scattered segments

    - by Christian Rau
    I got to solve a pretty standard problem on the GPU, but I'm quite new to practical GPGPU, so I'm looking for ideas to approach this problem. I have many points in 3-space which are assigned to a very small number of groups (each point belongs to one group), specifically 15 in this case (doesn't ever change). Now I want to compute the mean and covariance matrix of all the groups. So on the CPU it's roughly the same as: for each point p { mean[p.group] += p.pos; covariance[p.group] += p.pos * p.pos; ++count[p.group]; } for each group g { mean[g] /= count[g]; covariance[g] = covariance[g]/count[g] - mean[g]*mean[g]; } Since the number of groups is extremely small, the last step can be done on the CPU (I need those values on the CPU, anyway). The first step is actually just a segmented reduction, but with the segments scattered around. So the first idea I came up with, was to first sort the points by their groups. I thought about a simple bucket sort using atomic_inc to compute bucket sizes and per-point relocation indices (got a better idea for sorting?, atomics may not be the best idea). After that they're sorted by groups and I could possibly come up with an adaption of the segmented scan algorithms presented here. But in this special case, I got a very large amount of data per point (9-10 floats, maybe even doubles if the need arises), so the standard algorithms using a shared memory element per thread and a thread per point might make problems regarding per-multiprocessor resources as shared memory or registers (Ok, much more on compute capability 1.x than 2.x, but still). Due to the very small and constant number of groups I thought there might be better approaches. Maybe there are already existing ideas suited for these specific properties of such a standard problem. Or maybe my general approach isn't that bad and you got ideas for improving the individual steps, like a good sorting algorithm suited for a very small number of keys or some segmented reduction algorithm minimizing shared memory/register usage. I'm looking for general approaches and don't want to use external libraries. FWIW I'm using OpenCL, but it shouldn't really matter as the general concepts of GPU computing don't really differ over the major frameworks.

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  • Making a row of divs all be the same height using CSS

    - by pavel
    I have a row of divs that must all be the same height, but I have no way of knowing what that height might be ahead of time (the content comes from an external source). I initially tried placing the divs in an enclosing div and floated them left. I then set their height to be "100%", but this had no perceptible effect. By setting the height on the enclosing div to a fixed-height I could then get the floated divs to expand, but only up to the fixed height of the container. When the content in one of the divs exceeded the fixed height, it spilled over; the floated divs refused to expand. I Googled this floated-divs-of-the-same-height problem and apparently there's no way to do it using CSS. So now I am trying to use a combination of relative and absolute positioning instead of floats. This is the CSS: <style type="text/css"> div.container { background: #ccc; position: relative; min-height: 10em; } div.a { background-color: #aaa; position: absolute; top: 0px; left: 0px; bottom: 0px; width: 40%; } div.b { background-color: #bbb; position: absolute; top: 0px; left: 41%; bottom: 0px; width: 40%; } </style> This is a simplified version of the HTML: <div class="container"> <div class="a">Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Integer pretium dui sit amet felis. Integer sit amet diam. Phasellus ultrices viverra velit.</div> <div class="b">Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Integer pretium dui sit amet felis. Integer sit amet diam. Phasellus ultrices viverra velit. Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Integer pretium dui sit amet felis. Integer sit amet diam. Phasellus ultrices viverra velit.</div> </div> This works, unless you change the min-height to something like 5em (demonstranting what happens when the content exceeds the minimum height), and you can see that while the text doesn't get cutoff, the divs still refuse to expand. Now I am at a lose. Is there any way to do this using CSS?

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  • Can MySQL reasonably perform queries on billions of rows?

    - by haxney
    I am planning on storing scans from a mass spectrometer in a MySQL database and would like to know whether storing and analyzing this amount of data is remotely feasible. I know performance varies wildly depending on the environment, but I'm looking for the rough order of magnitude: will queries take 5 days or 5 milliseconds? Input format Each input file contains a single run of the spectrometer; each run is comprised of a set of scans, and each scan has an ordered array of datapoints. There is a bit of metadata, but the majority of the file is comprised of arrays 32- or 64-bit ints or floats. Host system |----------------+-------------------------------| | OS | Windows 2008 64-bit | | MySQL version | 5.5.24 (x86_64) | | CPU | 2x Xeon E5420 (8 cores total) | | RAM | 8GB | | SSD filesystem | 500 GiB | | HDD RAID | 12 TiB | |----------------+-------------------------------| There are some other services running on the server using negligible processor time. File statistics |------------------+--------------| | number of files | ~16,000 | | total size | 1.3 TiB | | min size | 0 bytes | | max size | 12 GiB | | mean | 800 MiB | | median | 500 MiB | | total datapoints | ~200 billion | |------------------+--------------| The total number of datapoints is a very rough estimate. Proposed schema I'm planning on doing things "right" (i.e. normalizing the data like crazy) and so would have a runs table, a spectra table with a foreign key to runs, and a datapoints table with a foreign key to spectra. The 200 Billion datapoint question I am going to be analyzing across multiple spectra and possibly even multiple runs, resulting in queries which could touch millions of rows. Assuming I index everything properly (which is a topic for another question) and am not trying to shuffle hundreds of MiB across the network, is it remotely plausible for MySQL to handle this? UPDATE: additional info The scan data will be coming from files in the XML-based mzML format. The meat of this format is in the <binaryDataArrayList> elements where the data is stored. Each scan produces = 2 <binaryDataArray> elements which, taken together, form a 2-dimensional (or more) array of the form [[123.456, 234.567, ...], ...]. These data are write-once, so update performance and transaction safety are not concerns. My naïve plan for a database schema is: runs table | column name | type | |-------------+-------------| | id | PRIMARY KEY | | start_time | TIMESTAMP | | name | VARCHAR | |-------------+-------------| spectra table | column name | type | |----------------+-------------| | id | PRIMARY KEY | | name | VARCHAR | | index | INT | | spectrum_type | INT | | representation | INT | | run_id | FOREIGN KEY | |----------------+-------------| datapoints table | column name | type | |-------------+-------------| | id | PRIMARY KEY | | spectrum_id | FOREIGN KEY | | mz | DOUBLE | | num_counts | DOUBLE | | index | INT | |-------------+-------------| Is this reasonable?

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  • Template class + virtual function = must implement?

    - by sold
    This code: template <typename T> struct A { T t; void DoSomething() { t.SomeFunction(); } }; struct B { }; A<B> a; is easily compiled without any complaints, as long as I never call a.DoSomething(). However, if I define DoSomething as a virtual function, I will get a compile error saying that B doesn't declare SomeFunction. I can somewhat see why it happens (DoSomething should now have an entry in the vtable), but I can't help feeling that it's not really obligated. Plus it sucks. Is there any way to overcome this? EDIT 2: Okay. I hope this time it makes sence: Let's say I am doing intrusive ref count, so all entities must inherit from base class Object. How can I suuport primitive types too? I can define: template <typename T> class Primitive : public Object { T value; public: Primitive(const T &value=T()); operator T() const; Primitive<T> &operator =(const T &value); Primitive<T> &operator +=(const T &value); Primitive<T> &operator %=(const T &value); // And so on... }; so I can use Primitive<int>, Primitive<char>... But how about Primitive<float>? It seems like a problem, because floats don't have a %= operator. But actually, it isn't, since I'll never call operator %= on Primitive<float>. That's one of the deliberate features of templates. If, for some reason, I would define operator %= as virtual. Or, if i'll pre-export Primitive<float> from a dll to avoid link errors, the compiler will complain even if I never call operator %= on a Primitive<float>. If it would just have fill in a dummy value for operator %= in Primitive<float>'s vtable (that raises an exception?), everything would have been fine.

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  • Line Graph CGPoints from NSMutableArray

    - by Mattog1456
    I have been trying to adapt the code from the accelerometer example such that when the user depresses a uibutton a point is added to a line graph. Working on the converting two floats, which are the result of calculate as below into a CGPoint and converting the CGPoint into an NSValue and then adding this to a NSMutableArray with the following -(IBAction)calculate:(id)sender { self.points = [NSMutableArray array]; CGPoint pt = CGPointMake(d, c); [self.points addObject:[NSValue valueWithCGPoint:pt]]; NSLog(@"%@", NSStringFromCGPoint(pt)); NSLog(@"%@", [NSString stringWithFormat:@"%d points", self.points.count ]); } But for some reason I am only getting one object stored in the array, it seems everytime push the calculate button the object pt gets overwritten, on the plus side it has the correct x,y coords. Any ideas on this one? UPDATE Removed self.points = [NSMutableArray array]; and placed it in view did load, also set the first points to 0,0. so that is working ok. Now the next problem is that I have a Graph subclass where the CG Drawing is taking place. I am trying to figure out a simple way to be able to access the above NSMutableArray which is in a ViewController class from the graph class. Am so close to the end but am really stuck, any help would be great. Still trying to draw a line graph on a UIView which is on a UIScrollview. The draw rect method is in the UIView Subclass and everything is working there, I have gridlines and labels on the axis and I can draw manually onto it. But the problem I have is that I cannot read the NSMutableArray of the CGPoints, which are the x and y coords. The ViewController performs a calculation and the results are written to the NSMutable array and this is all working fine as well, I can see the CGpoints and their values being written with NSLogs in the ViewController. I have tried various ways to set the NSMutableArray up as a global but to no avail, everything runs but while I can see the points being written in the ViewController they are just not visible to the UIView Subclass. I have also tried to use the addObserver and observeValueForKeyPath methods and once again while everything runs the subclass cannot see the array. Any ideas, suggestions, tips or thoughts would be great

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  • Is there a way to have element behind a div (links) clickable in areas where the div is "transparent

    - by Adam
    I have a block element that is positioned absolutely and some other elements on page that are positioned fixed. The effect is the block on top floats over the page which works well. The links in the elements at the bottom underneath are not clickable. They shouldn't be when the content of the div is over them, but when the "marginal" areas which are transparent are over the links they are visible, but clicks only register to the covering div. The problem only happens when the padding covers the div. But if I just rely on the margin the bottom margin is ignored by browser so the scroll doesn't go high enough up. To solve this I resort to padding at the bottom. This is the problem. Is there a clean way around this? I realize I could have the underneath elements doubled and place on top, but opacity set to 0. That is an undesirable solution however. Sample of the problem: <!DOCTYPE html> <html lang='en' xml:lang='en' xmlns='http://www.w3.org/1999/xhtml'> <head> <style> #top, #bottom { position: fixed; border: 1 px solid #333; background-color: #eee; left: 100px; padding: 8px; } #top { top: 0; z-index: 1; } #bottom { bottom: 0; z-index: 2; } #contentWrapper { position: absolute; margin: 100px 0 0 0; /* Padding is used to make sure the scroll goes up further on the page */ padding: 0 0 100px 0; width: 600px; z-index: 3; } #content { border: 1 px solid #333; background-color: #eee; height: 1000px; } </style> </head> <body> <div id='top'><a href="#">Top link</a></div> <div id='bottom'><a href="#">Bottom link</a></div> <div id='contentWrapper'> <div id='content'>Some content</div> </div> </body> </html>

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  • CodePlex Daily Summary for Sunday, September 29, 2013

    CodePlex Daily Summary for Sunday, September 29, 2013Popular ReleasesAudioWordsDownloader: AudioWordsDownloader 1.1 build 88: New features -------- list of words (mp3 files) is available upon typing when a download path is defined list of download paths is added paths history settings added Bug fixed ----- case mismatch in word search field fixed path not exist bug fixed when history has been used path, when filled from dialog, not stored refresh autocomplete list after path change word sought is deleted when path is changed at the end sought word list is deleted word list not refreshed download end...Activity Viewer 2012: Activity Viewer 2012 V 5.0.0.3: Planning to add new features: 1. Import/Export rules 2. Tabular mode multi servers connections.Tweetinvi a friendly Twitter C# API: Alpha 0.8.3.0: Version 0.8.3.0 emphasis on the FIlteredStream and ease how to manage Exceptions that can occur due to the network or any other issue you might encounter. Will be available through nuget the 29/09/2013. FilteredStream Features provided by the Twitter Stream API - Ability to track specific keywords - Ability to track specific users - Ability to track specific locations Additional features - Detect the reasons the tweet has been retrieved from the Filtered API. You have access to both the ma...AcDown?????: AcDown????? v4.5: ??●AcDown??????????、??、??、???????。????,????,?????????????????????????。???????????Acfun、????(Bilibili)、??、??、YouTube、??、???、??????、SF????、????????????。 ●??????AcPlay?????,??????、????????????????。 ● AcDown???????C#??,????.NET Framework 2.0??。?????"Acfun?????"。 ??v4.5 ???? AcPlay????????v3.5 ????????,???????????30% ?? ???????GoodManga.net???? ?? ?????????? ?? ??Acfun?????????? ??Bilibili??????????? ?????????flvcd???????? ??SfAcg????????????? ???????????? ???????????????? ????32...OfflineBrowser: Release v1.2: This release includes some multi-threading support, a better progress bar, more JavaScript fixes, and a help system. This release is also portable (can run with no issues from a flash drive).CtrlAltStudio Viewer: CtrlAltStudio Viewer 1.0.0.34288 Release: This release of the CtrlAltStudio Viewer includes the following significant features: Stereoscopic 3D display support. Based on Firestorm viewer 4.4.2 codebase. For more details, see the release notes linked to below. Release notes: http://ctrlaltstudio.com/viewer/release-notes/1-0-0-34288-release Support info: http://ctrlaltstudio.com/viewer/support Privacy policy: http://ctrlaltstudio.com/viewer/privacy Disclaimer: This software is not provided or supported by Linden Lab, the makers of ...CrmSvcUtil Generate Attribute Constants: Generate Attribute Constants (1.0.5018.28159): Built against version 5.0.15 of the CRM SDK Fixed issue where constant for primary key attribute was being duplicated in all entity classes Added ability to override base class for entity classesC# Intellisense for Notepad++: Release v1.0.6.0: Added support for classless scripts To avoid the DLLs getting locked by OS use MSI file for the installation.CS-Script for Notepad++: Release v1.0.6.0: Added support for classless scripts To avoid the DLLs getting locked by OS use MSI file for the installation.SimpleExcelReportMaker: Serm 0.02: SourceCode and SampleMagick.NET: Magick.NET 6.8.7.001: Magick.NET linked with ImageMagick 6.8.7.0. Breaking changes: - ToBitmap method of MagickImage returns a png instead of a bmp. - Changed the value for full transparency from 255(Q8)/65535(Q16) to 0. - MagickColor now uses floats instead of Byte/UInt16.Media Companion: Media Companion MC3.578b: With the feedback received over the renaming of Movie Folders, and files, there has been some refinement done. As well as I would like to introduce Blu-Ray movie folder support, for Pre-Frodo and Frodo onwards versions of XBMC. To start with, Context menu option for renaming movies, now has three sub options: Movie & Folder, Movie only & Folder only. The option Manual Movie Rename needs to be selected from Movie Preferences, but the autoscrape boxes do not need to be selected. Blu Ray Fo...WDTVHubGen - Adds Metadata, thumbnails and subtitles to WDTV Live Hubs: WDTVHubGen v2.1.3.api release: This is for the brave at heart, this is the maint release to update to the new movie api. please send feedback on fix requests.FFXIV Crafting Simulator: Crafting Simulator 2.3: - Major refactoring of the code behind. - Added a current durability and a current CP textbox.DNN CMS Platform: 07.01.02: Major HighlightsAdded the ability to manage the Vanity URL prefix Added the ability to filter members in the member directory by role Fixed issue where the user could inadvertently click the login button multiple times Fixed issues where core classes could not be used in out of process cache provider Fixed issue where profile visibility submenu was not displayed correctly Fixed issue where the member directory was broken when Convert URL to lowercase setting was enabled Fixed issu...Rawr: Rawr 5.4.1: This is the Downloadable WPF version of Rawr!For web-based version see http://elitistjerks.com/rawr.php You can find the version notes at: http://rawr.codeplex.com/wikipage?title=VersionNotes Rawr Addon (NOT UPDATED YET FOR MOP)We now have a Rawr Official Addon for in-game exporting and importing of character data hosted on Curse. The Addon does not perform calculations like Rawr, it simply shows your exported Rawr data in wow tooltips and lets you export your character to Rawr (including ba...Sample MVC4 EF Codefirst Architecture: RazMVCWebApp ver 1.1: Signal R sample is added.CODE Framework: 4.0.30923.0: See change notes in the documentation section for details on what's new. Note: If you download the class reference help file with, you have to right-click the file, pick "Properties", and then unblock the file, as many browsers flag the file as blocked during download (for security reasons) and thus hides all content.JayData -The unified data access library for JavaScript: JayData 1.3.2 - Indian Summer Edition: JayData is a unified data access library for JavaScript to CRUD + Query data from different sources like WebAPI, OData, MongoDB, WebSQL, SQLite, HTML5 localStorage, Facebook or YQL. The library can be integrated with KendoUI, Angular.js, Knockout.js or Sencha Touch 2 and can be used on Node.js as well. See it in action in this 6 minutes video KendoUI examples: JayData example site Examples for map integration JayData example site What's new in JayData 1.3.2 - Indian Summer Edition For detai...ZXing.Net: ZXing.Net 0.12.0.0: sync with rev. 2892 of the java version new PDF417 decoder improved Aztec decoder global speed improvements direct Kinect support for ColorImageFrame better Structured Append support many other small bug fixes and improvementsNew ProjectsCACHEDB: CLIENT-DATABASE || CLIENT_CACHEDB-DATABASEClassic WiX Burn Theme: A WiX Burn theme inspired by the classic WiX wizard user interface.CryptStr.Fody: A post-build weaver that encrypts literal strings in your .NET assemblies without breaking ClickOnce.Easy Code: A setting framework.EduSoft: This is a school eg.GameStuff: GameStuff is a library of Physics and Geometrics concepts for video game. Nekora Test Project: Nekora test projectPopCorn Console Game: Simple console gameRadioController: This project started from people installing Tablets in Mustangs. You would typically loose most control of the radio. This projects brings that back!Random searcher i pochodne: Wyszukiwarka plików multimedialnych i czego dusza zapragnie.SporkRandom: A .NET (C#, Visual Basic) interface for the true random number generator service of random.org

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  • C#/.NET Little Wonders: Interlocked Read() and Exchange()

    - by James Michael Hare
    Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. Last time we discussed the Interlocked class and its Add(), Increment(), and Decrement() methods which are all useful for updating a value atomically by adding (or subtracting).  However, this begs the question of how do we set and read those values atomically as well? Read() – Read a value atomically Let’s begin by examining the following code: 1: public class Incrementor 2: { 3: private long _value = 0; 4:  5: public long Value { get { return _value; } } 6:  7: public void Increment() 8: { 9: Interlocked.Increment(ref _value); 10: } 11: } 12:  It uses an interlocked increment, as we discuss in my previous post (here), so we know that the increment will be thread-safe.  But, to realize what’s potentially wrong we have to know a bit about how atomic reads are in 32 bit and 64 bit .NET environments. When you are dealing with an item smaller or equal to the system word size (such as an int on a 32 bit system or a long on a 64 bit system) then the read is generally atomic, because it can grab all of the bits needed at once.  However, when dealing with something larger than the system word size (reading a long on a 32 bit system for example), it cannot grab the whole value at once, which can lead to some problems since this read isn’t atomic. For example, this means that on a 32 bit system we may read one half of the long before another thread increments the value, and the other half of it after the increment.  To protect us from reading an invalid value in this manner, we can do an Interlocked.Read() to force the read to be atomic (of course, you’d want to make sure any writes or increments are atomic also): 1: public class Incrementor 2: { 3: private long _value = 0; 4:  5: public long Value 6: { 7: get { return Interlocked.Read(ref _value); } 8: } 9:  10: public void Increment() 11: { 12: Interlocked.Increment(ref _value); 13: } 14: } Now we are guaranteed that we will read the 64 bit value atomically on a 32 bit system, thus ensuring our thread safety (assuming all other reads, writes, increments, etc. are likewise protected).  Note that as stated before, and according to the MSDN (here), it isn’t strictly necessary to use Interlocked.Read() for reading 64 bit values on 64 bit systems, but for those still working in 32 bit environments, it comes in handy when dealing with long atomically. Exchange() – Exchanges two values atomically Exchange() lets us store a new value in the given location (the ref parameter) and return the old value as a result. So just as Read() allows us to read atomically, one use of Exchange() is to write values atomically.  For example, if we wanted to add a Reset() method to our Incrementor, we could do something like this: 1: public void Reset() 2: { 3: _value = 0; 4: } But the assignment wouldn’t be atomic on 32 bit systems, since the word size is 32 bits and the variable is a long (64 bits).  Thus our assignment could have only set half the value when a threaded read or increment happens, which would put us in a bad state. So instead, we could write Reset() like this: 1: public void Reset() 2: { 3: Interlocked.Exchange(ref _value, 0); 4: } And we’d be safe again on a 32 bit system. But this isn’t the only reason Exchange() is valuable.  The key comes in realizing that Exchange() doesn’t just set a new value, it returns the old as well in an atomic step.  Hence the name “exchange”: you are swapping the value to set with the stored value. So why would we want to do this?  Well, anytime you want to set a value and take action based on the previous value.  An example of this might be a scheme where you have several tasks, and during every so often, each of the tasks may nominate themselves to do some administrative chore.  Perhaps you don’t want to make this thread dedicated for whatever reason, but want to be robust enough to let any of the threads that isn’t currently occupied nominate itself for the job.  An easy and lightweight way to do this would be to have a long representing whether someone has acquired the “election” or not.  So a 0 would indicate no one has been elected and 1 would indicate someone has been elected. We could then base our nomination strategy as follows: every so often, a thread will attempt an Interlocked.Exchange() on the long and with a value of 1.  The first thread to do so will set it to a 1 and return back the old value of 0.  We can use this to show that they were the first to nominate and be chosen are thus “in charge”.  Anyone who nominates after that will attempt the same Exchange() but will get back a value of 1, which indicates that someone already had set it to a 1 before them, thus they are not elected. Then, the only other step we need take is to remember to release the election flag once the elected thread accomplishes its task, which we’d do by setting the value back to 0.  In this way, the next thread to nominate with Exchange() will get back the 0 letting them know they are the new elected nominee. Such code might look like this: 1: public class Nominator 2: { 3: private long _nomination = 0; 4: public bool Elect() 5: { 6: return Interlocked.Exchange(ref _nomination, 1) == 0; 7: } 8: public bool Release() 9: { 10: return Interlocked.Exchange(ref _nomination, 0) == 1; 11: } 12: } There’s many ways to do this, of course, but you get the idea.  Running 5 threads doing some “sleep” work might look like this: 1: var nominator = new Nominator(); 2: var random = new Random(); 3: Parallel.For(0, 5, i => 4: { 5:  6: for (int j = 0; j < _iterations; ++j) 7: { 8: if (nominator.Elect()) 9: { 10: // elected 11: Console.WriteLine("Elected nominee " + i); 12: Thread.Sleep(random.Next(100, 5000)); 13: nominator.Release(); 14: } 15: else 16: { 17: // not elected 18: Console.WriteLine("Did not elect nominee " + i); 19: } 20: // sleep before check again 21: Thread.Sleep(1000); 22: } 23: }); And would spit out results like: 1: Elected nominee 0 2: Did not elect nominee 2 3: Did not elect nominee 1 4: Did not elect nominee 4 5: Did not elect nominee 3 6: Did not elect nominee 3 7: Did not elect nominee 1 8: Did not elect nominee 2 9: Did not elect nominee 4 10: Elected nominee 3 11: Did not elect nominee 2 12: Did not elect nominee 1 13: Did not elect nominee 4 14: Elected nominee 0 15: Did not elect nominee 2 16: Did not elect nominee 4 17: ... Another nice thing about the Interlocked.Exchange() is it can be used to thread-safely set pretty much anything 64 bits or less in size including references, pointers (in unsafe mode), floats, doubles, etc.  Summary So, now we’ve seen two more things we can do with Interlocked: reading and exchanging a value atomically.  Read() and Exchange() are especially valuable for reading/writing 64 bit values atomically in a 32 bit system.  Exchange() has value even beyond simply atomic writes by using the Exchange() to your advantage, since it reads and set the value atomically, which allows you to do lightweight nomination systems. There’s still a few more goodies in the Interlocked class which we’ll explore next time! Technorati Tags: C#,CSharp,.NET,Little Wonders,Interlocked

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