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  • What hash algorithms are paralellizable? Optimizing the hashing of large files utilizing on mult-co

    - by DanO
    I'm interested in optimizing the hashing of some large files (optimizing wall clock time). The I/O has been optimized well enough already and the I/O device (local SSD) is only tapped at about 25% of capacity, while one of the CPU cores is completely maxed-out. I have more cores available, and in the future will likely have even more cores. So far I've only been able to tap into more cores if I happen to need multiple hashes of the same file, say an MD5 AND a SHA256 at the same time. I can use the same I/O stream to feed two or more hash algorithms, and I get the faster algorithms done for free (as far as wall clock time). As I understand most hash algorithms, each new bit changes the entire result, and it is inherently challenging/impossible to do in parallel. Are any of the mainstream hash algorithms parallelizable? Are there any non-mainstream hashes that are parallelizable (and that have at least a sample implementation available)? As future CPUs will trend toward more cores and a leveling off in clock speed, is there any way to improve the performance of file hashing? (other than liquid nitrogen cooled overclocking?) or is it inherently non-parallelizable?

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  • Bandpass filter of FFT applied image. (Like ImageJ bandpass filter algorithm)

    - by maximus
    There is a good function that I need, which is implemented in Java program: ImageJ I need to understand the algorithm used there. The function has several parameters: link text And before using FFT it converts image to a special one: The Bandpass Filter uses a special algorithm to reduce edge artifacts (before the Fourier transform, the image is extended in size by attaching mirrored copies of image parts outside the original image, thus no jumps occur at the edges) Can you tell me more about this special transform? Actually tiling mirrored image. I am writing on C++ and wish to rewrite that part of the program on C++.

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  • Edit axes to an image in matlab ?

    - by ZaZu
    Hello, I would like to edit the axes in my series of images being displayed .. This is how my image looks like : As you can see, it starts from 0 to ~~500 from top to bottom, can I invert that ? Plus I want to mirror the image being shown, so that it starts from left to right ... Or if its possible, let the axes show from right to left ? Thanks !

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  • What's the fastest way to approximate the period of data using Octave?

    - by John
    I have a set of data that is periodic (but not sinusoidal). I have a set of time values in one vector and a set of amplitudes in a second vector. I'd like to quickly approximate the period of the function. Any suggestions? Specifically, here's my current code. I'd like to approximate the period of the vector x(:,2) against the vector t. Ultimately, I'd like to do this for lots of initial conditions and calculate the period of each and plot the result. function xdot = f (x,t) xdot(1) =x(2); xdot(2) =-sin(x(1)); endfunction x0=[1;1.75]; #eventually, I'd like to try lots of values for x0(2) t = linspace (0, 50, 200); x = lsode ("f", x0, t) plot(x(:,1),x(:,2)); Thank you! John

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  • How to decide between using PLINQ and LINQ at runtime?

    - by Hamish Grubijan
    Or decide between a parallel and a sequential operation in general. It is hard to know without testing whether parallel or sequential implementation is best due to overhead. Obviously it will take some time to train "the decider" which method to use. I would say that this method cannot be perfect, so it is probabilistic in nature. The x,y,z do influence "the decider". I think a very naive implementation would be to give both 1/2 chance at the beginning and then start favoring them according to past performance. This disregards x,y,z, however. I suspect that this question would be better answered by academics than practitioners. Anyhow, please share your heuristic, your experience if any, your tips on this. Sample code: public interface IComputer { decimal Compute(decimal x, decimal y, decimal z); } public class SequentialComputer : IComputer { public decimal Compute( ... // sequential implementation } public class ParallelComputer : IComputer { public decimal Compute( ... // parallel implementation } public class HybridComputer : IComputer { private SequentialComputer sc; private ParallelComputer pc; private TheDecider td; // Helps to decide between the two. public HybridComputer() { sc = new SequentialComputer(); pc = new ParallelComputer(); td = TheDecider(); } public decimal Compute(decimal x, decimal y, decimal z) { decimal result; decimal time; if (td.PickOneOfTwo() == 0) { // Time this and save result into time. result = sc.Compute(...); } else { // Time this and save result into time. result = pc.Compute(); } td.Train(time); return result; } }

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  • how to generate large image in compact framework

    - by Buthrakaur
    I need to generate large images (A4 image at 200 DPI, PNG format would be fine) in my compact framework application. This is impossible to do in standard way due to memory limitations (such big image will throw OOMException). Is there any library which offers file-backed stream image generation? Or I could generate many smaller stripes of images (each stripe representing a row of the large image) using standard Bitmap approach, but I need to merge them together afterwards - is there any method how to merge many smaller images into one large without having to instantiate large Bitmap instance (which would again cause OOM)?

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  • How to do motion tracking of a object using video

    - by Niroshan
    Could someone direct me to a tutorial or guide me how to track motion of a object moving with 6 DOF. I am planing to use a video stream of a moving toy car. I want to calculate displacement and rotation angle of the toy car. I came across some research papers but couldn't find any libraries to the job. Is there a way to do this using OpenCV or Matlab or some other freely available software? Thank you

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  • On-the-fly thumbnails PHP

    - by Wayne
    I came up with this: <?php $dir = $_GET['dir']; header('Content-type: image/jpeg'); $create = imagecreatetruecolor(150, 150); $img = imagecreatefromjpeg($dir); imagecopyresampled($create, $img, 0, 0, 0, 0, 150, 150, 150, 150); imagejpeg($create, null, 100); ?> It works by accessing: http://domain.com/image.php?dir=thisistheimage.jpg Which works fine... but the output is awful: Can someone fix my code for the image to be 150 x 150 covering the black area... Thanks.

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  • Identifying idle state on a windows machine

    - by SaM
    I know about the GetLastInputInfo method but that would only give me the duration since last user input - keyboard or mouse. If a user input was last received 10 minutes ago, that wouldn't mean the system has been idle for 10 minutes - scans, downloads, movies - lots of reasons. So how can we identify whether the system is truly idle or not? Does anyone know what Window's definition of "idle" is? Must be a combination of thresholds - like less than 5% cpu util, less than 3% disk util etc. - along with the user input parameter...anyone knows the exact definition?

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  • Track Pedestrians

    - by 2vision2
    I am using OpenCV sample code “peopledetect.cpp” to detect and track pedestrians. The code uses HoG for feature extraction and SVM for classification. Please find the reference paper used here. The camera is mounted on the wall at a height of 10 feet and 45 degree down. There is no restriction on the pedestrian movement within the frame. I want to track the detected pedestrians’ movement within the frame. The issue I am facing is pedestrians are detected only in the middle region of the frame as most of the features are not visible as soon as the pedestrian enters the frame region. I want to track each person’s movement in the entire frame region. How to do it? Is tracking required? Can anyone give any reference to blogs/codes?

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  • Android Out of memory regarding png image

    - by turtleboy
    I have a jpg image in my app that shows correctly. In my listview i'd like to make the image more transparent so it is easier to see the text. I changed the image to a png format and altered it's opacity in GIMP. Now that the new image is in the app drawable folder. Im getting the following error. why? 09-28 09:24:07.560: I/global(20140): call socket shutdown, tmpsocket=Socket[address=/178.250.50.40,port=80,localPort=35172] 09-28 09:24:07.570: I/global(20140): call socket shutdown, tmpsocket=Socket[address=/212.169.27.217,port=84,localPort=55656] 09-28 09:24:07.690: D/dalvikvm(20140): GC_FOR_ALLOC freed 113K, 4% free 38592K/39907K, paused 32ms 09-28 09:24:07.690: I/dalvikvm-heap(20140): Forcing collection of SoftReferences for 28072816-byte allocation 09-28 09:24:07.740: D/dalvikvm(20140): GC_BEFORE_OOM freed 9K, 4% free 38582K/39907K, paused 43ms 09-28 09:24:07.740: E/dalvikvm-heap(20140): Out of memory on a 28072816-byte allocation. 09-28 09:24:07.740: I/dalvikvm(20140): "main" prio=5 tid=1 RUNNABLE 09-28 09:24:07.740: I/dalvikvm(20140): | group="main" sCount=0 dsCount=0 obj=0x40a57490 self=0x1b6e9a8 09-28 09:24:07.740: I/dalvikvm(20140): | sysTid=20140 nice=0 sched=0/0 cgrp=default handle=1074361640 09-28 09:24:07.740: I/dalvikvm(20140): | schedstat=( 2289118000 760844000 2121 ) utm=195 stm=33 core=1 09-28 09:24:07.740: I/dalvikvm(20140): at android.graphics.BitmapFactory.nativeDecodeAsset(Native Method) 09-28 09:24:07.740: I/dalvikvm(20140): at android.graphics.BitmapFactory.decodeResourceStream(BitmapFactory.java:486) 09-28 09:24:07.740: I/dalvikvm(20140): at android.graphics.drawable.Drawable.createFromResourceStream(Drawable.java:773) 09-28 09:24:07.740: I/dalvikvm(20140): at android.content.res.Resources.loadDrawable(Resources.java:2042) 09-28 09:24:07.740: I/dalvikvm(20140): at android.content.res.TypedArray.getDrawable(TypedArray.java:601) 09-28 09:24:07.740: I/dalvikvm(20140): at android.view.View.<init>(View.java:2812) 09-28 09:24:07.740: I/dalvikvm(20140): at android.view.ViewGroup.<init>(ViewGroup.java:410) 09-28 09:24:07.740: I/dalvikvm(20140): at android.widget.LinearLayout.<init>(LinearLayout.java:174) 09-28 09:24:07.740: I/dalvikvm(20140): at android.widget.LinearLayout.<init>(LinearLayout.java:170) 09-28 09:24:07.740: I/dalvikvm(20140): at java.lang.reflect.Constructor.constructNative(Native Method) 09-28 09:24:07.740: I/dalvikvm(20140): at java.lang.reflect.Constructor.newInstance(Constructor.java:417) 09-28 09:24:07.740: I/dalvikvm(20140): at android.view.LayoutInflater.createView(LayoutInflater.java:586) 09-28 09:24:07.740: I/dalvikvm(20140): at com.android.internal.policy.impl.PhoneLayoutInflater.onCreateView(PhoneLayoutInflater.java:56) 09-28 09:24:07.740: I/dalvikvm(20140): at android.view.LayoutInflater.onCreateView(LayoutInflater.java:653) 09-28 09:24:07.740: I/dalvikvm(20140): at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:678) 09-28 09:24:07.740: I/dalvikvm(20140): at android.view.LayoutInflater.inflate(LayoutInflater.java:466) 09-28 09:24:07.740: I/dalvikvm(20140): at android.view.LayoutInflater.inflate(LayoutInflater.java:396) 09-28 09:24:07.740: I/dalvikvm(20140): at android.view.LayoutInflater.inflate(LayoutInflater.java:352) 09-28 09:24:07.740: I/dalvikvm(20140): at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:278) 09-28 09:24:07.740: I/dalvikvm(20140): at android.app.Activity.setContentView(Activity.java:1897) 09-28 09:24:07.740: I/dalvikvm(20140): at com.carefreegroup.ShowMoreDetails.onCreate(ShowMoreDetails.java:26) 09-28 09:24:07.740: I/dalvikvm(20140): at android.app.Activity.performCreate(Activity.java:4543) 09-28 09:24:07.740: I/dalvikvm(20140): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1071) 09-28 09:24:07.740: I/dalvikvm(20140): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2181) 09-28 09:24:07.740: I/dalvikvm(20140): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2260) 09-28 09:24:07.740: I/dalvikvm(20140): at android.app.ActivityThread.access$600(ActivityThread.java:139) 09-28 09:24:07.740: I/dalvikvm(20140): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1277) 09-28 09:24:07.740: I/dalvikvm(20140): at android.os.Handler.dispatchMessage(Handler.java:99) 09-28 09:24:07.740: I/dalvikvm(20140): at android.os.Looper.loop(Looper.java:156) 09-28 09:24:07.740: I/dalvikvm(20140): at android.app.ActivityThread.main(ActivityThread.java:5045) 09-28 09:24:07.740: I/dalvikvm(20140): at java.lang.reflect.Method.invokeNative(Native Method) 09-28 09:24:07.740: I/dalvikvm(20140): at java.lang.reflect.Method.invoke(Method.java:511) 09-28 09:24:07.740: I/dalvikvm(20140): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 09-28 09:24:07.740: I/dalvikvm(20140): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 09-28 09:24:07.740: I/dalvikvm(20140): at dalvik.system.NativeStart.main(Native Method) 09-28 09:24:07.740: E/dalvikvm(20140): Out of memory: Heap Size=46115KB, Allocated=38582KB, Limit=65536KB 09-28 09:24:07.740: E/dalvikvm(20140): Extra info: Footprint=39907KB, Allowed Footprint=46115KB, Trimmed=892KB 09-28 09:24:07.740: E/Bitmap_JNI(20140): Create Bitmap Failed. 09-28 09:24:07.740: A/libc(20140): Fatal signal 11 (SIGSEGV) at 0x00000004 (code=1) 09-28 09:24:09.750: I/dalvikvm(20367): Turning on JNI app bug workarounds for target SDK version 10... 09-28 09:24:09.940: D/dalvikvm(20367): GC_CONCURRENT freed 864K, 21% free 3797K/4771K, paused 2ms+2ms thanks. [update] @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.showmoredetailslayout); actualCallTime = (TextView)findViewById(R.id.actualcalltime); doubleUp = (TextView)findViewById(R.id.doubleupcallid); needName = (TextView)findViewById(R.id.needname); needNameLabel = (TextView)findViewById(R.id.neednamelabel); getRotaDetails = (Button)findViewById(R.id.buttongetrotadetails); intent = this.getIntent(); String actualTimeIn = intent.getStringExtra("actTimeIn"); String actualTimeOut = intent.getStringExtra("actTimeOut"); String doubleUpValue = intent.getStringExtra("doubleUpValue"); String needNameWithCommas = intent.getStringExtra("needNameWithCommas"); callID = intent.getStringExtra("callID"); String[] needs = needNameWithCommas.split(","); actualCallTime.setText("This call was completed at " + actualTimeIn + " -" + actualTimeOut); if( ! doubleUpValue.equalsIgnoreCase("") || doubleUpValue.equalsIgnoreCase("]")){ doubleUp.setText("This call was not a double up "); }else{ doubleUp.setText("This call was a double up " + doubleUpValue); } needNameLabel.setText("Purpose of Call: "); for (int i = 0; i < needs.length; i++){ needName.append( needs[i] + "\n"); } getRotaDetails.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { Intent intent = new Intent(ShowMoreDetails.this, GetRotaDetails.class); intent.putExtra("callIDExtra", callID); startActivity(intent); } }); } }

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  • Codeigniter Image Library Cropping an Image with 2 sets of coordinates to make square anywhere?

    - by chris
    Spending time reading through the docs, and searching for examples. I understand cropping an image from top 0, and left 0 is pretty straight forward. However. I would like to pass 2 sets of coordinates, a starting point and an ending point. Four Points, a Square that is defined anywhere. However from the examples I am finding, and from what I gather the rendition is not going to let me do this. codeigniter so I am seeking confirmation on this thought, is it true that I can only provide end points from 0, and it crops a square based on said end points or can I actually specify an x start, an x end, and similar for y? Or is there some other technique I can use within codeigniter that will allow me to pass for coordinates for starting and ending points?

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  • Windows Azure: Parallelization of the code

    - by veda
    I have some matrix multiplication operation. I want to parallelize the execution of those operations through multiple processors.. This can be done on high performance computing cluster using MPI (Message Passing Interface). Like wise, can I do some parallelization in the cloud using multiple worker roles. Is there any means for doing that.

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  • Opencv video frame not showing Sobel output

    - by user1016950
    This is a continuation question from Opencv video frame giving me an error I think I closed it off, Im new to Stackoverflow. I have code below that Im trying to see its Sobel edge image. However the program runs but the output is just a grey screen where if I mouseover the cursor disappears. Does anyone see the error? or is it a misunderstanding about the data structures Im using IplImage *frame, *frame_copy = 0; // capture frames from video CvCapture *capture = cvCaptureFromFile( "lightinbox1.avi"); //Allows Access to video propertys cvQueryFrame(capture); //Get the number of frames int nframe=(int) cvGetCaptureProperty(capture,CV_CAP_PROP_FRAME_COUNT); //Name window cvNamedWindow( "video:", 1 ); //start loop for(int i=0;i<nframe;i++){ //prepare capture frame extraction cvGrabFrame(capture); cout<<"We are on frame "<<i<<"\n"; //Get this frame frame = cvRetrieveFrame( capture ); con2txt(frame); frame_copy = cvCreateImage(cvSize(frame->width,frame->height),IPL_DEPTH_8U,frame->nChannels ); //show and destroy frame cvCvtColor( frame,frame,CV_RGB2GRAY); //Create Sobel output frame_copy1 = cvCreateImage(cvSize(frame->width,frame->height),IPL_DEPTH_16S,1 ); cvSobel(frame_copy,frame_copy1,2,2,3); cvShowImage("video:",frame_copy1); cvWaitKey(33);} cvReleaseCapture(&capture);

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  • Problem with thumbnails after newly added - PHP on-the-fly method

    - by Wayne
    Hey again... to those that may have read my previous question that got solved a couple minutes ago .< The on-the-fly php script works perfectly, but when I went to upload new images into a gallery which I made myself, the images are resized to 150 x 150 for what I wanted... however, when it comes to new images being added it is all black... As you can see the three black images that were uploaded to the folder and the directory added to the database. What is causing this? If I view the source, the code is fine... the while loop in the PHP generates an output like this: <div class="view-wrap" id="photo-10"> <div class="view-icon"> <div class="img-label"> <a href="#" id="10" class="delete"><img src="img/small-delete.png" /> Delete</a> </div> <a href="img/events/Paintballing/24251_1395408043148_1170626626_1204038_5382765_n.jpg"> <img src="image.php?dir=img/events/Paintballing/24251_1395408043148_1170626626_1204038_5382765_n.jpg" alt="" width="110" height="110" /> </a> </div> </div> An example of one block. If I view the source (in Firefox) and click on the image.php?dir=img/events/Paintballing/24251_1395408043148_1170626626_1204038_5382765_n.jpg by exmaple, I can see the thumbnail at it's 150 x 150 size but in the layout, it shows a black thumbnail... Does anyone know why this is happening?

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  • C# Combining lines

    - by Mike
    Hey everybody, this is what I have going on. I have two text files. Umm lets call one A.txt and B.txt. A.txt is a config file that contains a bunch of folder names, only 1 listing per folder. B.txt is a directory listing that contains folders names and sizes. But B contains a bunch of listing not just 1 entry. What I need is if B, contains A. Take all lines in B that contain A and write it out as A|B|B|B ect.... So example: A.txt: Apple Orange Pear XBSj HEROE B.txt: Apple|3123123 Apple|3434 Orange|99999999 Orange|1234544 Pear|11 Pear|12 XBSJ|43949 XBSJ|43933 Result.txt: Apple|3123123|3434 Orange|99999999|1234544 Pear|11|12 XBSJ|43949|43933 This is what I had but it's not really doing what I needed. string[] combineconfig = File.ReadAllLines(@"C:\a.txt"); foreach (string ccline in combineconfig) { string[] readlines = File.ReadAllLines(@"C:\b.txt"); if (readlines.Contains(ccline)) { foreach (string rdlines in readlines) { string[] pslines = rdlines.Split('|'); File.AppendAllText(@"C:\result.txt", ccline + '|' + pslines[0]); } } I know realize it's not going to find the first "if" because it reads the entire line and cant find it. But i still believe my output file will not contain what I need.

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  • Standardizing camera input in OpenCV? (Contrast/Saturation/Brightness etc..)

    - by karpathy
    I am building an application using OpenCV that uses the webcam and runs some vision algorithms. I would like to make this application available on the internet after I am done, but I am concerned about the vast differences in camera settings on every computer, and I am worried that the algorithm may break if the settings are too different from mine. Is there any way, after capturing the frame, to post process it and make sure that the contrast is X, brightness is Y, and saturation is Z? I think the Camera settings themselves can not be changed from code directly using the current OpenCV Python bindings. Would anyone be able to tell me about how I could calculate some of these parameters from the image and adjust them appropriately using OpenCV?

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  • detect the most used colour in an image using python

    - by sree01
    Hi, I want to find the most used colour in an image using python. for example detect the colour of the object in the following image http://www.shopcrazy.com.ph/wp-content/images/2007/02/shiny-bags-01.jpg. how to detect the base colour from the RGB codes(example - red in the above image).

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