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• What do gurus say about Requirements Traceability Matrix?

  - by Jaywalker

  Our organization is at CMMI Level 2, and as part of the requirements of the level, we have to maintain an RTM which more or less contains the following entries for each requirement: Requirement Description Reference Section Functional Specification Document Reference Section Design Document Reference Section Test Cases Document Now, this might be an overkill for a small project. But more importantly, this could be a nightmare to maintain when the requirements/ features keep changing, and documents have to be constantly updated. What do the gurus say about this? Should one avoid such level of documentation or are there any tools to manage when a "change" out dates so many artifacts? And by using the term 'gurus', I am not talking of coding champs; rather people like Steve McConnel or others who have worked on commercial projects of medium to large scale. Quotes/ book references/ articles will suit me. EDIT: It's not just requirements that change. Design Document can change; well, even test cases may change.

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• Models from 3ds max lose their transformations when input into XNA

  - by jacobian

  I am making models in 3ds max. However when I export them to .fbx format and then input them into XNA, they lose their scaling. -It is most likely something to do with not using the transforms from the model correctly, is the following code correct -using xna 3.0 Matrix[] transforms=new Matrix[playerModel.Meshes.Count]; playerModel.CopyAbsoluteBoneTransformsTo(transforms); // Draw the model. int count = 0; foreach (ModelMesh mesh in playerModel.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.World = transforms[count]* Matrix.CreateScale(scale) * Matrix.CreateRotationX((float)MathHelper.ToRadians(rx)) * Matrix.CreateRotationY((float)MathHelper.ToRadians(ry)) * Matrix.CreateRotationZ((float)MathHelper.ToRadians(rz))* Matrix.CreateTranslation(position); effect.View = view; effect.Projection = projection; effect.EnableDefaultLighting(); } count++; mesh.Draw(); }

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• deteminant of matrix

  - by davit-datuashvili

  suppose there is given two dimensional array int a[][]=new int[4][4]; i am trying to find determinant of matrices please help i know how find it mathematical but i am trying to find it in programaticaly

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• WinForm resizing matrix?

  - by serhio

  WinForms question: Is there a way to keep elements at a proportional distance when the parent form(or panel) is resized?

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• transforming 1d (1column) into 5d(5column) matrix through copy paste or other

  - by Curious

  Ex. I want to take the column with 12345..... and order 5 columns across as seen. next 5 numbers in column will be next row. However my code creates a 4 row gap in between each successive row. I dont know what additional logic (possibly if then statement) I can embed into do loop to may make it cleaner. I am new to this, so showing as much sample code to learn the syntax would be most beneficial. thanks in advance. Below is the Result of my code. VBA code is below result. 1 1 2 3 4 5 2 3 4 5 6 6 7 8 9 10 7 8 9 10 11 11 12 13 14 15 12 13 14 15 16 16 17 17 Sub Working_Code() ' Working_Code Macro Do ActiveCell.Select Selection.Copy ActiveCell.Offset(0, 5).Select ActiveSheet.Paste ActiveCell.Offset(1, -5).Select Selection.Copy ActiveCell.Offset(-1, 6).Select ActiveSheet.Paste ActiveCell.Offset(2, -6).Select Selection.Copy ActiveCell.Offset(-2, 7).Select ActiveSheet.Paste ActiveCell.Offset(3, -7).Select Selection.Copy ActiveCell.Offset(-3, 8).Select ActiveSheet.Paste ActiveCell.Offset(4, -8).Select Selection.Copy ActiveCell.Offset(-4, 9).Select ActiveSheet.Paste ActiveCell.Offset(5, -9).Select Loop Until IsEmpty(ActiveCell.Offset(0, -1)) End Sub

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• 2D pixel array rotation and scaling

  - by Betamoo

  Hi I am working on C# program to process images ( given as int[,] ).. So I have 2D array of pixels, and I need to rotate them around a point, then scale them down to fit the original array.. I already found articles about using matrix to transform to a point and rotate then transform back.. What remains is to scale the resultant image to fit an array of original size.. How that can be done? (preferably with 2 equations one for x and one for y ) Thanks in advance

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• ILNumerics multiply complex with matrix<double>

  - by nik

  I m looking at ILNumerics to translate some matlab code into c#. How would I multiply a complex and a double? Simplified description: In Matlab: A=[1 2 3] i*A*A' Returns a complex number. How would I do the same in ILNumerics: ILArray<double> A = ILMath.array(1.0, 2.0, 3.0); complex B = complex.i * ILMath.multiply(A,A.T); Throws the error: Operator '*' cannot be applied to operands of type 'ILNumerics.complex' and 'ILNumerics.ILRetArray<double>' Update This works: double C = 14.0; complex D = complex.i * C; But shouldnt: ILMath.multiply(A,A.T) also return 14.0?

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• Indexing one-dimensional numpy.array as matrix

  - by Alain

  I am trying to index a numpy.array with varying dimensions during runtime. To retrieve e.g. the first row of a n*m array a, you can simply do a[0,:] However, in case a happens to be a 1xn vector, this code above returns an index error: IndexError: too many indices As the code needs to be executed as efficiently as possible I don't want to introduce an if statement. Does anybody have a convenient solution that ideally doesn't involve changing any data structure types?

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• Error " Index exceeds Matrix dimensions"

  - by Mola

  Hi experts, I am trying to read an excel 2003 file which consist of 62 columns and 2000 rows and then draw 2d dendrogram from 2000 pattern of 2 categories of a data as my plot in matlab. When i run the script, it gives me the above error. I don't know why. Anybody has any idea why i have the above error? My data is here: http://rapidshare.com/files/383549074/data.xls Please delete the 2001 column if you want to use the data for testing. and my code is here: % Script file: cluster_2d_data.m d=2000; n1=22; n2=40; N=62 Data=xlsread('data.xls','A1:BJ2000'); X=Data'; R=1:2000; C=1:2; clustergram(X,'Pdist','euclidean','Linkage','complete','Dimension',2,... 'ROWLABELS',R,'COLUMNLABELS',C,'Dendrogram',{'color',5})

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• printf'ing a matrix

  - by Flavius

  I'm trying to implement an all-purpose function for printing 2D data. What I've come up with is: int mprintf(FILE* f, char* fmt, void** data, size_t cols, size_t rows) The challenge is determining how many bits to read at once from data, based on fmt. The format fmt is going to be the stdlib's-specific format for printf() and alike. Do you have any knowledge of already-existing features from stdlibc (GNU GCC C's) I could use to ease this up? I try avoiding having to do it all manually, because I know "I am stupid" (I don't want to introduce stupid bugs). Thus, reusing code would be the bug-freest way. Thanks Addendum I see there's a /usr/include/printf.h. Can't I use any of those functions to do it right and ease my job at the same time?

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• Help Please, I want use LINQ to Query Count in a matrix according to a array!

  - by Bob Feng

  I have a matrix, IEnumerable<IEnumerable<int>> matrix, for example: { {10,23,16,20,2,4}, {22,13,1,33,21,11 }, {7,19,31,12,6,22}, ... } and another array: int[] arr={ 10, 23, 16, 20} I want to filter the matrix on the condition that I group all rows of the matrix which contain the same number of elements from arr. That is to say the first row in the matrix {10,23,16,20,2,4} has 4 numbers from arr, this array should be grouped with the rest of the rows with 4 numbers from arr. better to use linq, thank you very much!

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• i want to multiply a character L to identity matrix in c#

  - by vj4u

  for (int row = 0; row < SS; row++) { for (int col = 0; col < SS; col++) { identity[row, col] = (row == col) ? 1 : 0; Response.Write(identity[row, col] + " "); } Response.Write("<br/>"); } now my output is 1 0 0 0 1 0 0 0 1 i want to get output as L 0 0 0 L 0 0 0 L

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• Twisted Matrix and telnet server implementation

  - by ypercube

  I have a project which is essentially a game server where users connect and send text commands via telnet. The code is in C and really old and unmodular and has several bugs and missing features. The main function alone is half the code. I came to the conclusion that rewriting it in TwistedMachine could actually result in faster completement, besides other benefits. So, here is the questions: What packages and modules I should use? I see a "telnet" module inside "protocols" package. I also see "cronch" package with "ssh" and another "telnet" module. I'm a complete novice regarding Python.

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• How to create a matrix format in perl

  - by shaq

  I have an array of array in which each array is like: clusterA gene1 1 clusterA gene2 0 clusterB gene1 1 clusterB gene2 0 I want to produce a file like: name gene1 gene2 clusterA 1 0 clusterB 1 0 Current attempt: if (condition) { @array = ($cluster, $genes, "1"); } elsif (not condition) { @array = ($cluster, $genes, "0"); } push @AoA, [ @array ]; @A0A is my array of array.

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• Improve C function performance with cache locality?

  - by Christoper Hans

  I have to find a diagonal difference in a matrix represented as 2d array and the function prototype is int diagonal_diff(int x[512][512]) I have to use a 2d array, and the data is 512x512. This is tested on a SPARC machine: my current timing is 6ms but I need to be under 2ms. Sample data: [3][4][5][9] [2][8][9][4] [6][9][7][3] [5][8][8][2] The difference is: |4-2| + |5-6| + |9-5| + |9-9| + |4-8| + |3-8| = 2 + 1 + 4 + 0 + 4 + 5 = 16 In order to do that, I use the following algorithm: int i,j,result=0; for(i=0; i<4; i++) for(j=0; j<4; j++) result+=abs(array[i][j]-[j][i]); return result; But this algorithm keeps accessing the column, row, column, row, etc which make inefficient use of cache. Is there a way to improve my function?

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• How to hard define in code a matrix Integer[][]

  - by Pentium10

  Question is simple for an expert: Integer[][] res= new Integer[][] {.....hard code some values here on 2 dim...} How to I return here 2 rows and 3 values like this 1 2 3 4 5 6

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• putting data from a for loop into a table using matlab and fprintf

  - by user2928537

  I am trying to put the following data from my for loop into a table formatted so that there are 11 values of F in each column, with a total of 4 columns. but I am always ending up with one long column of my data instead of the four columns I want. I was wondering if there is some way to put the data into a matrix and then reshape it, but I am having trouble. Any help greatly appreciated. fprintf ('Electrostatic Forces:\n') for r = 1:4; q2 = 0: 1*10^-19: 1*10^-18; for F = coulomb(q2,r); fprintf ('%d\n',F) end end Where the code for the function coulomb is function F = coulomb (q2,r); k = 8.98*10^9; q1 = 1.6*10^-19; F = k*abs(q1*q2)/r^2; end

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• Need help with testdisk output

  - by dan

  I had (note the past tense) an ubuntu 12.04 system with separate partitions for the base and /home directories. It started acting wonky, so I decided to do a reinstall with 12.10, intending just to do a reinstall to the base partition. After several seconds, I realize that the installer was repartitioning the drive and reinstalling, so I pulled the power cord. I'm now trying to recover as much as I can with testdisk, but it seems that testdisk is finding 100 unique partitions when I run it - they mostly tend to be HFS+ or solaris /home (which I think is just an ext4; I've never had solaris on the machine). I've pasted an abbreviated version of the testdisk output below (first ~100 lines, and then ~100 lines from the middle of the output). Is there a way to combine or recreate the partitions and then data recovery, or some other way maximize what I can recover (ideally as much of the file system as possible)? I really only care about what was in the /home directory - I'd rather not use photorec since I don't have another 2 TB HD lying around to recover to. Thanks, Dan Mon Dec 10 06:03:00 2012 Command line: TestDisk TestDisk 6.13, Data Recovery Utility, November 2011 Christophe GRENIER <[email protected]> http://www.cgsecurity.org OS: Linux, kernel 3.2.34-std312-amd64 (#2 SMP Sat Nov 17 08:06:32 UTC 2012) x86_64 Compiler: GCC 4.4 Compilation date: 2012-11-27T22:44:52 ext2fs lib: 1.42.6, ntfs lib: libntfs-3g, reiserfs lib: 0.3.1-rc8, ewf lib: none /dev/sda: LBA, HPA, LBA48, DCO support /dev/sda: size 3907029168 sectors /dev/sda: user_max 3907029168 sectors /dev/sda: native_max 3907029168 sectors Warning: can't get size for Disk /dev/mapper/control - 0 B - CHS 1 1 1, sector size=512 /dev/sr0 is not an ATA disk Hard disk list Disk /dev/sda - 2000 GB / 1863 GiB - CHS 243201 255 63, sector size=512 - WDC WD20EARS-00J2GB0, S/N:WD-WCAYY0075071, FW:80.00A80 Disk /dev/sdb - 1013 MB / 967 MiB - CHS 1014 32 61, sector size=512 - Generic Flash Disk, FW:8.07 Disk /dev/sr0 - 367 MB / 350 MiB - CHS 179470 1 1 (RO), sector size=2048 - PLDS DVD+/-RW DH-16AAS, FW:JD12 Partition table type (auto): Intel Disk /dev/sda - 2000 GB / 1863 GiB - WDC WD20EARS-00J2GB0 Partition table type: EFI GPT Analyse Disk /dev/sda - 2000 GB / 1863 GiB - CHS 243201 255 63 Current partition structure: Bad GPT partition, invalid signature. search_part() Disk /dev/sda - 2000 GB / 1863 GiB - CHS 243201 255 63 recover_EXT2: s_block_group_nr=0/14880, s_mnt_count=5/4294967295, s_blocks_per_group=32768, s_inodes_per_group=8192 recover_EXT2: s_blocksize=4096 recover_EXT2: s_blocks_count 487593984 recover_EXT2: part_size 3900751872 MS Data 2048 3900753919 3900751872 EXT4 Large file Sparse superblock, 1997 GB / 1860 GiB Linux Swap 3900755968 3907028975 6273008 SWAP2 version 1, 3211 MB / 3062 MiB Results P MS Data 2048 3900753919 3900751872 EXT4 Large file Sparse superblock, 1997 GB / 1860 GiB P Linux Swap 3900755968 3907028975 6273008 SWAP2 version 1, 3211 MB / 3062 MiB interface_write() 1 P MS Data 2048 3900753919 3900751872 2 P Linux Swap 3900755968 3907028975 6273008 search_part() Disk /dev/sda - 2000 GB / 1863 GiB - CHS 243201 255 63 recover_EXT2: s_block_group_nr=0/14880, s_mnt_count=5/4294967295, s_blocks_per_group=32768, s_inodes_per_group=8192 recover_EXT2: s_blocksize=4096 recover_EXT2: s_blocks_count 487593984 recover_EXT2: part_size 3900751872 MS Data 2048 3900753919 3900751872 EXT4 Large file Sparse superblock, 1997 GB / 1860 GiB block_group_nr 1 recover_EXT2: "e2fsck -b 32768 -B 4096 device" may be needed recover_EXT2: s_block_group_nr=1/14880, s_mnt_count=0/4294967295, s_blocks_per_group=32768, s_inodes_per_group=8192 recover_EXT2: s_blocksize=4096 recover_EXT2: s_blocks_count 487593984 recover_EXT2: part_size 3900751872 MS Data 2046 3900753917 3900751872 EXT4 Large file Sparse superblock Backup superblock, 1997 GB / 1860 GiB block_group_nr 1 recover_EXT2: "e2fsck -b 32768 -B 4096 device" may be needed recover_EXT2: s_block_group_nr=1/14880, s_mnt_count=0/4294967295, s_blocks_per_group=32768, s_inodes_per_group=8192 recover_EXT2: s_blocksize=4096 recover_EXT2: s_blocks_count 487593984 recover_EXT2: part_size 3900751872 MS Data 2048 3900753919 3900751872 EXT4 Large file Sparse superblock Backup superblock, 1997 GB / 1860 GiB block_group_nr 1 recover_EXT2: "e2fsck -b 32768 -B 4096 device" may be needed recover_EXT2: s_block_group_nr=1/14584, s_mnt_count=0/27, s_blocks_per_group=32768, s_inodes_per_group=8192 recover_EXT2: s_blocksize=4096 recover_EXT2: s_blocks_count 477915164 recover_EXT2: part_size 3823321312 MS Data 4094 3823325405 3823321312 EXT4 Large file Sparse superblock Backup superblock, 1957 GB / 1823 GiB block_group_nr 1 ....snip...... MS Data 2046 3900753917 3900751872 EXT4 Large file Sparse superblock Backup superblock, 1997 GB / 1860 GiB MS Data 2048 3900753919 3900751872 EXT4 Large file Sparse superblock, 1997 GB / 1860 GiB MS Data 4094 3823325405 3823321312 EXT4 Large file Sparse superblock Backup superblock, 1957 GB / 1823 GiB MS Data 4096 3823325407 3823321312 EXT4 Large file Sparse superblock Backup superblock, 1957 GB / 1823 GiB MS Data 7028840 7033383 4544 FAT12, 2326 KB / 2272 KiB Mac HFS 67856948 67862179 5232 HFS+ found using backup sector!, 2678 KB / 2616 KiB Mac HFS 67862176 67867407 5232 HFS+, 2678 KB / 2616 KiB Mac HFS 67862244 67867475 5232 HFS+ found using backup sector!, 2678 KB / 2616 KiB Mac HFS 67867404 67872635 5232 HFS+, 2678 KB / 2616 KiB Mac HFS 67867472 67872703 5232 HFS+, 2678 KB / 2616 KiB Mac HFS 67872700 67877931 5232 HFS+, 2678 KB / 2616 KiB Mac HFS 67937834 67948067 10234 [EasyInstall_OSX] HFS found using backup sector!, 5239 KB / 5117 KiB Mac HFS 67938012 67948155 10144 HFS+ found using backup sector!, 5193 KB / 5072 KiB Mac HFS 67948064 67958297 10234 [EasyInstall_OSX] HFS, 5239 KB / 5117 KiB Mac HFS 67948070 67958303 10234 [EasyInstall_OSX] HFS found using backup sector!, 5239 KB / 5117 KiB Mac HFS 67948152 67958295 10144 HFS+, 5193 KB / 5072 KiB Mac HFS 67958292 67968435 10144 HFS+, 5193 KB / 5072 KiB Mac HFS 67958300 67968533 10234 [EasyInstall_OSX] HFS, 5239 KB / 5117 KiB Mac HFS 67992596 67997827 5232 HFS+ found using backup sector!, 2678 KB / 2616 KiB Mac HFS 67997824 68003055 5232 HFS+, 2678 KB / 2616 KiB Mac HFS 67997892 68003123 5232 HFS+ found using backup sector!, 2678 KB / 2616 KiB Mac HFS 68003052 68008283 5232 HFS+, 2678 KB / 2616 KiB Mac HFS 68003120 68008351 5232 HFS+, 2678 KB / 2616 KiB Mac HFS 68008348 68013579 5232 HFS+, 2678 KB / 2616 KiB Solaris /home 84429840 123499141 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84429952 123499253 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84493136 123562437 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84493248 123562549 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84566088 123635389 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84566200 123635501 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84571232 123640533 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84571344 123640645 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84659952 123729253 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84660064 123729365 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84690504 123759805 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84690616 123759917 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84700424 123769725 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84700536 123769837 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84797720 123867021 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84797832 123867133 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84812544 123881845 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84812656 123881957 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84824552 123893853 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84824664 123893965 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84847528 123916829 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84847640 123916941 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84886840 123956141 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84886952 123956253 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84945488 124014789 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84945600 124014901 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84957992 124027293 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84958104 124027405 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84962240 124031541 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84962352 124031653 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84977168 124046469 39069302 UFS1, 20 GB / 18 GiB Solaris /home 84977280 124046581 39069302 UFS1, 20 GB / 18 GiB MS Data 174395467 178483851 4088385 ..... snip (it keeps going on for quite a while)

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• My OpenCL kernel is slower on faster hardware.. But why?

  - by matdumsa

  Hi folks, As I was finishing coding my project for a multicore programming class I came up upon something really weird I wanted to discuss with you. We were asked to create any program that would show significant improvement in being programmed for a multi-core platform. I’ve decided to try and code something on the GPU to try out OpenCL. I’ve chosen the matrix convolution problem since I’m quite familiar with it (I’ve parallelized it before with open_mpi with great speedup for large images). So here it is, I select a large GIF file (2.5 MB) [2816X2112] and I run the sequential version (original code) and I get an average of 15.3 seconds. I then run the new OpenCL version I just wrote on my MBP integrated GeForce 9400M and I get timings of 1.26s in average.. So far so good, it’s a speedup of 12X!! But now I go in my energy saver panel to turn on the “Graphic Performance Mode” That mode turns off the GeForce 9400M and turns on the Geforce 9600M GT my system has. Apple says this card is twice as fast as the integrated one. Guess what, my timing using the kick-ass graphic card are 3.2 seconds in average… My 9600M GT seems to be more than two times slower than the 9400M.. For those of you that are OpenCL inclined, I copy all data to remote buffers before starting, so the actual computation doesn’t require roundtrip to main ram. Also, I let OpenCL determine the optimal local-worksize as I’ve read they’ve done a pretty good implementation at figuring that parameter out.. Anyone has a clue? edit: full source code with makefiles here http://www.mathieusavard.info/convolution.zip cd gimage make cd ../clconvolute make put a large input.gif in clconvolute and run it to see results

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• Performing a SVD on tweets. Memory problem

  - by plotti

  I have generated a huge csv file as an output from my pos tagging and stemming. It looks like this: word1, word2, word3, ..., word14400 person1 1 2 0 1 person2 0 0 1 0 ... person650 It contains the word counts for each person. Like this I am getting characteristic vectors for each person. I want to run a SVD on this beast, but it seems the matrix is too big to be held in memory to perform the operation. My quesion is: should i reduce the column size by removing words which have a column sum of for example 1, which means that they have been used only once. Do I bias the data too much with this attempt? I tried the rapidminer attempt, by loading the csv into the db. and then sequentially reading it in with batches for processing, like rapidminer proposes. But Mysql can't store that many columns in a table. If i transpose the data, and then retranspose it on import it also takes ages.... -- So in general I am asking for advice how to perform a svd on such a corpus.

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• Is there any function in Matlab for changing the form of matrix?

  - by niko

  Hi, I have to get the unknown matrix by changing the form of known matrix considering the following rules: H = [-P'|I] G = [I|P] where H is known matrix G is unknown matrix which has to be calculated I is identity matrix So for example if we had a matrix H = [1 1 1 1 0 0; 0 0 1 1 0 1; 1 0 0 1 1 0] its form has to be changed to H = [1 1 1 1 0 0; 0 1 1 0 1 0; 1 1 0 0 0 1] so -P' = [1 1 1; 0 1 0; 1 1 0] and in case of binary matrices -P = P therefore G = [1 0 0 1 1 1; 0 1 0 0 1 0; 0 0 1 1 1 0] I know how to solve it on the paper by performing basic row operations but don't know how if there is any function already written in Matlab to calculate G from H or H from G by considering the above rules. I would be very thankful if anyone of you could suggest any method for solving the given problem. Thank you.

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• iPhone: How to use CGContextConcatCTM for saving a transformed image properly?

  - by Irene

  I am making an iPhone application that loads an image from the camera, and then the user can select a second image from the library, move/scale/rotate that second image, and then save the result. I use two UIImageViews in IB as placeholders, and then apply transformations while touching/pinching. The problem comes when I have to save both images together. I use a rect of the size of the first image and pass it to UIGraphicsBeginImageContext. Then I tried to use CGContextConcatCTM but I can't understand how it works: CGRect rect = CGRectMake(0, 0, img1.size.width, img1.size.height); // img1 from camera UIGraphicsBeginImageContext(rect.size); // Start drawing CGContextRef ctx = UIGraphicsGetCurrentContext(); CGContextClearRect(ctx, rect); // Clear whole thing [img1 drawAtPoint:CGPointZero]; // Draw background image at 0,0 CGContextConcatCTM(ctx, img2.transform); // Apply the transformations of the 2nd image But what do I need to do next? What information is being held in the img2.transform matrix? The documentation for CGContextConcatCTM doesn't help me that much unfortunately.. Right now I'm trying to solve it by calculating the points and the angle using trigonometry (with the help of this answer), but since the transformation is there, there has to be an easier and more elgant way to do this, right?

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• Why does mmap() fail with ENOMEM on a 1TB sparse file?

  - by metadaddy

  I've been working with large sparse files on openSUSE 11.2 x86_64. When I try to mmap() a 1TB sparse file, it fails with ENOMEM. I would have thought that the 64 bit address space would be adequate to map in a terabyte, but it seems not. Experimenting further, a 1GB file works fine, but a 2GB file (and anything bigger) fails. I'm guessing there might be a setting somewhere to tweak, but an extensive search turns up nothing. Here's some sample code that shows the problem - any clues? #include <errno.h> #include <fcntl.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/mman.h> #include <sys/types.h> #include <unistd.h> int main(int argc, char *argv[]) { char * filename = argv[1]; int fd; off_t size = 1UL << 40; // 30 == 1GB, 40 == 1TB fd = open(filename, O_RDWR | O_CREAT | O_TRUNC, 0666); ftruncate(fd, size); printf("Created %ld byte sparse file\n", size); char * buffer = (char *)mmap(NULL, (size_t)size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); if ( buffer == MAP_FAILED ) { perror("mmap"); exit(1); } printf("Done mmap - returned 0x0%lx\n", (unsigned long)buffer); strcpy( buffer, "cafebabe" ); printf("Wrote to start\n"); strcpy( buffer + (size - 9), "deadbeef" ); printf("Wrote to end\n"); if ( munmap(buffer, (size_t)size) < 0 ) { perror("munmap"); exit(1); } close(fd); return 0; }

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• Help me get my 3D camera to look like the ones in RTS

  - by rFactor

  I am a newbie in 3D game development and I am trying to make a real-time strategy game. I am struggling with the camera currently as I am unable to make it look like they do in RTS games. Here is my Camera.cs class using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Input; namespace BB { public class Camera : Microsoft.Xna.Framework.GameComponent { public Matrix view; public Matrix projection; protected Game game; KeyboardState currentKeyboardState; Vector3 cameraPosition = new Vector3(600.0f, 0.0f, 600.0f); Vector3 cameraForward = new Vector3(0, -0.4472136f, -0.8944272f); BoundingFrustum cameraFrustum = new BoundingFrustum(Matrix.Identity); // Light direction Vector3 lightDir = new Vector3(-0.3333333f, 0.6666667f, 0.6666667f); public Camera(Game game) : base(game) { this.game = game; } public override void Initialize() { this.view = Matrix.CreateLookAt(this.cameraPosition, this.cameraPosition + this.cameraForward, Vector3.Up); this.projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, this.game.renderer.aspectRatio, 1, 10000); base.Initialize(); } /* Handles the user input * @ param GameTime gameTime */ private void HandleInput(GameTime gameTime) { float time = (float)gameTime.ElapsedGameTime.TotalMilliseconds; currentKeyboardState = Keyboard.GetState(); } void UpdateCamera(GameTime gameTime) { float time = (float)gameTime.ElapsedGameTime.TotalMilliseconds; // Check for input to rotate the camera. float pitch = 0.0f; float turn = 0.0f; if (currentKeyboardState.IsKeyDown(Keys.Up)) pitch += time * 0.001f; if (currentKeyboardState.IsKeyDown(Keys.Down)) pitch -= time * 0.001f; if (currentKeyboardState.IsKeyDown(Keys.Left)) turn += time * 0.001f; if (currentKeyboardState.IsKeyDown(Keys.Right)) turn -= time * 0.001f; Vector3 cameraRight = Vector3.Cross(Vector3.Up, cameraForward); Vector3 flatFront = Vector3.Cross(cameraRight, Vector3.Up); Matrix pitchMatrix = Matrix.CreateFromAxisAngle(cameraRight, pitch); Matrix turnMatrix = Matrix.CreateFromAxisAngle(Vector3.Up, turn); Vector3 tiltedFront = Vector3.TransformNormal(cameraForward, pitchMatrix * turnMatrix); // Check angle so we cant flip over if (Vector3.Dot(tiltedFront, flatFront) > 0.001f) { cameraForward = Vector3.Normalize(tiltedFront); } // Check for input to move the camera around. if (currentKeyboardState.IsKeyDown(Keys.W)) cameraPosition += cameraForward * time * 0.4f; if (currentKeyboardState.IsKeyDown(Keys.S)) cameraPosition -= cameraForward * time * 0.4f; if (currentKeyboardState.IsKeyDown(Keys.A)) cameraPosition += cameraRight * time * 0.4f; if (currentKeyboardState.IsKeyDown(Keys.D)) cameraPosition -= cameraRight * time * 0.4f; if (currentKeyboardState.IsKeyDown(Keys.R)) { cameraPosition = new Vector3(0, 50, 50); cameraForward = new Vector3(0, 0, -1); } cameraForward.Normalize(); // Create the new view matrix view = Matrix.CreateLookAt(cameraPosition, cameraPosition + cameraForward, Vector3.Up); // Set the new frustum value cameraFrustum.Matrix = view * projection; } public override void Update(Microsoft.Xna.Framework.GameTime gameTime) { HandleInput(gameTime); UpdateCamera(gameTime); } } } The problem is that the initial view is looking in a horizontal direction. I would like to have an RTS like top down view (but with a slight pitch). Can you help me out?

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• Printing out variables in c changes values of variables

  - by George Wilson

  I have an odd problem with some c-programme here. I was getting some wrong values in a matrix I was finding the determinant of and so I started printing variables - yet found that by printing values out the actual values in the code changed. I eventually narrowed it down to one specific printf statement - highlighted in the code below. If I comment out this line then I start getting incorrect values in my determinent calculations, yet by printing it out I get the value out I expect Code below: #include <math.h> #include <stdio.h> #include <stdlib.h> #define NUMBER 15 double determinant_calculation(int size, double array[NUMBER][NUMBER]); int main() { double array[NUMBER][NUMBER], determinant_value; int size; array[0][0]=1; array[0][1]=2; array[0][2]=3; array[1][0]=4; array[1][1]=5; array[1][2]=6; array[2][0]=7; array[2][1]=8; array[2][2]=10; size=3; determinant_value=determinant_calculation(size, array); printf("\n\n\n\n\n\nDeterminant value is %lf \n\n\n\n\n\n", determinant_value); return 0; } double determinant_calculation(int size, double array[NUMBER][NUMBER]) { double determinant_matrix[NUMBER][NUMBER], determinant_value; int x, y, count=0, sign=1, i, j; /*initialises the array*/ for (i=0; i<(NUMBER); i++) { for(j=0; j<(NUMBER); j++) { determinant_matrix[i][j]=0; } } /*does the re-cursion method*/ for (count=0; count<size; count++) { x=0; y=0; for (i=0; i<size; i++) { for(j=0; j<size; j++) { if (i!=0&&j!=count) { determinant_matrix[x][y]=array[i][j]; if (y<(size-2)) { y++; } else { y=0; x++; } } } } //commenting this for loop out changes the values of the code determinent prints -7 when commented out and -3 (expected) when included! for (i=0; i<size; i++) { for(j=0; j<size; j++){ printf("%lf ", determinant_matrix[i][j]); } printf("\n"); } if(size>2) { determinant_value+=sign*(array[0][count]*determinant_calculation(size-1 ,determinant_matrix)); } else { determinant_value+=sign*(array[0][count]*determinant_matrix[0][0]); } sign=-1*sign; } return (determinant_value); } I know its not the prettiest (or best way) of doing what I'm doing with this code but it's what I've been given - so can't make huge changes. I don't suppose anyone could explain why printing out the variables can actually change the values? or how to fix it because ideally i don't want to!!

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