All geek questions in one place

Access to dgemm in C ++

I need to implement a matrix class in C ++, and one of the operations should be matrix multiplication via dgemm. My professor made an example in a class in C, but for some reason I cannot get it to work in C ++. This is my header.h file:

#include <iostream> #include <stdlib.h> extern "C" { #include "blas.h" } [blah blah blah, matrix class here; overloaded * operator will do the matrix multiplication] matrix operator* (const matrix &other){ matrix AxB(Nrows, other.Ncolumns, "(" + name + "*" + "other.name" + ")"); char TRANSA = 'N'; char TRANSB = 'N'; int M = Nrows; int N = other.Ncolumns; int K = Ncolumns; double alpha = 1.; double beta = 0.; dgemm_ (&TRANSA, &TRANSB, &M, &N, &K, &alpha, data, &M, other.data, &K, &beta, AxB.data, &M); return AxB; [blah blah blah, overloaded = operator here; i'm positive this is not the problem since it works for matrix addition]

The main function:

 #include "matrix.h" main(){ // entries of A and B are randomized between 0 and 1 matrix A(5,5); matrix B(5,5); matrix C = A*B; }

Now the blas.h file header:

 void dgemm_ (char *TRANSA, char *TRANSB, int *M, int *N, int *K, double *ALPHA, double **A, int *LDA, double **B, int *LDB, double *BETA, double **C, int *LDC);

I use the routine described here: http://www.netlib.org/blas/dgemm.f

Basically, the way we did this in the class for implementing C built the matrix as one long array using (double *) calloc (rows * columns, sizeof (double)).

My C ++ implementation does:

 double **data; data = new double[rows]; for(int i=1; i<=rows; ++i){ data[i-1] = new double[columns]; }

and then I can index the data [i] [j]. But since the dgemm routine should accept double * A, double * B, etc., But my matrices are double ** A, etc., How can I fix this?

This is the error message I get from valgrind:

 ==18845== Invalid write of size 8 ==18845== at 0x4165C1C: ATL_dgezero (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x4149DA7: ATL_dNCmmJIK (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x415BE8E: ATL_dgemm (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x4182F54: ATL_dptgemm_nt (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4183140: ATL_dptgemm (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x40818F6: atl_f77wrap_dgemm_ (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4E4E0004: ??? ==18845== Address 0x478d680 is 8 bytes after a block of size 16 alloc'd ==18845== at 0x402B454: operator new[](unsigned int) (in /usr/lib/valgrind /vgpreload_memcheck-x86-linux.so) ==18845== by 0x8049045: dmatrix::dmatrix(int, int, std::string) (dmatrix.hpp:77) ==18845== by 0x8049532: dmatrix::operator*(dmatrix const&) (dmatrix.hpp:218) ==18845== by 0x8048DCB: main (main.cpp:17) ==18845== ==18845== Invalid write of size 8 ==18845== at 0x4165C1F: ATL_dgezero (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x4149DA7: ATL_dNCmmJIK (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x415BE8E: ATL_dgemm (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x4182F54: ATL_dptgemm_nt (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4183140: ATL_dptgemm (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x40818F6: atl_f77wrap_dgemm_ (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4E4E0004: ??? ==18845== Address 0x478d678 is 0 bytes after a block of size 16 alloc'd ==18845== at 0x402B454: operator new[](unsigned int) (in /usr/lib/valgrind /vgpreload_memcheck-x86-linux.so) ==18845== by 0x8049045: dmatrix::dmatrix(int, int, std::string) (dmatrix.hpp:77) ==18845== by 0x8049532: dmatrix::operator*(dmatrix const&) (dmatrix.hpp:218) ==18845== by 0x8048DCB: main (main.cpp:17) ==18845== ==18845== Invalid write of size 8 ==18845== at 0x4165C22: ATL_dgezero (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x4149DA7: ATL_dNCmmJIK (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x415BE8E: ATL_dgemm (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x4182F54: ATL_dptgemm_nt (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4183140: ATL_dptgemm (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x40818F6: atl_f77wrap_dgemm_ (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4E4E0004: ??? ==18845== Address 0x478d690 is not stack'd, malloc'd or (recently) free'd ==18845== ==18845== Invalid write of size 8 ==18845== at 0x4165C25: ATL_dgezero (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x4149DA7: ATL_dNCmmJIK (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x415BE8E: ATL_dgemm (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x4182F54: ATL_dptgemm_nt (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4183140: ATL_dptgemm (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x40818F6: atl_f77wrap_dgemm_ (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4E4E0004: ??? ==18845== Address 0x478d688 is not stack'd, malloc'd or (recently) free'd ==18845== ==18845== Invalid read of size 8 ==18845== at 0x4143D60: ATL_dJIK0x0x0NN0x0x0_aX_bX (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4149A9D: ATL_dNCmmJIK (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x415BE8E: ATL_dgemm (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x4182F54: ATL_dptgemm_nt (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4183140: ATL_dptgemm (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x40818F6: atl_f77wrap_dgemm_ (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4E4E0004: ??? ==18845== Address 0x478cf80 is not stack'd, malloc'd or (recently) free'd ==18845== ==18845== Invalid read of size 8 ==18845== at 0x4143D64: ATL_dJIK0x0x0NN0x0x0_aX_bX (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4149A9D: ATL_dNCmmJIK (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x415BE8E: ATL_dgemm (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x4182F54: ATL_dptgemm_nt (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4183140: ATL_dptgemm (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x40818F6: atl_f77wrap_dgemm_ (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4E4E0004: ??? ==18845== Address 0x478d130 is 0 bytes after a block of size 16 alloc'd ==18845== at 0x402B454: operator new[](unsigned int) (in /usr/lib/valgrind /vgpreload_memcheck-x86-linux.so) ==18845== by 0x8049045: dmatrix::dmatrix(int, int, std::string) (dmatrix.hpp:77) ==18845== by 0x8048D49: main (main.cpp:6) ==18845== ==18845== Invalid read of size 8 ==18845== at 0x4143D4C: ATL_dJIK0x0x0NN0x0x0_aX_bX (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4149A9D: ATL_dNCmmJIK (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x415BE8E: ATL_dgemm (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x4182F54: ATL_dptgemm_nt (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4183140: ATL_dptgemm (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x40818F6: atl_f77wrap_dgemm_ (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4E4E0004: ??? ==18845== Address 0x478d678 is 0 bytes after a block of size 16 alloc'd ==18845== at 0x402B454: operator new[](unsigned int) (in /usr/lib/valgrind /vgpreload_memcheck-x86-linux.so) ==18845== by 0x8049045: dmatrix::dmatrix(int, int, std::string) (dmatrix.hpp:77) ==18845== by 0x8049532: dmatrix::operator*(dmatrix const&) (dmatrix.hpp:218) ==18845== by 0x8048DCB: main (main.cpp:17) ==18845== ==18845== Invalid write of size 8 ==18845== at 0x4143D93: ATL_dJIK0x0x0NN0x0x0_aX_bX (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4149A9D: ATL_dNCmmJIK (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x415BE8E: ATL_dgemm (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x4182F54: ATL_dptgemm_nt (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4183140: ATL_dptgemm (in /usr/lib/atlas-base/atlas/libblas.so.3gf.0) ==18845== by 0x40818F6: atl_f77wrap_dgemm_ (in /usr/lib/atlas-base/atlas /libblas.so.3gf.0) ==18845== by 0x4E4E0004: ??? ==18845== Address 0x478d678 is 0 bytes after a block of size 16 alloc'd ==18845== at 0x402B454: operator new[](unsigned int) (in /usr/lib/valgrind /vgpreload_memcheck-x86-linux.so) ==18845== by 0x8049045: dmatrix::dmatrix(int, int, std::string) (dmatrix.hpp:77) ==18845== by 0x8049532: dmatrix::operator*(dmatrix const&) (dmatrix.hpp:218) ==18845== by 0x8048DCB: main (main.cpp:17) ==18845== ==18845== Invalid read of size 8 ==18845== at 0x8048DEA: main (main.cpp:19) ==18845== Address 0x0 is not stack'd, malloc'd or (recently) free'd ==18845== ==18845== ==18845== Process terminating with default action of signal 11 (SIGSEGV) ==18845== Access not within mapped region at address 0x0 ==18845== at 0x8048DEA: main (main.cpp:19) ==18845== If you believe this happened as a result of a stack ==18845== overflow in your program main thread (unlikely but ==18845== possible), you can try to increase the size of the ==18845== main thread stack using the --main-stacksize= flag. ==18845== The main thread stack size used in this run was 8388608. ==18845== ==18845== HEAP SUMMARY: ==18845== in use at exit: 3,581 bytes in 39 blocks ==18845== total heap usage: 49 allocs, 10 frees, 7,760 bytes allocated ==18845== ==18845== LEAK SUMMARY: ==18845== definitely lost: 128 bytes in 4 blocks ==18845== indirectly lost: 0 bytes in 0 blocks ==18845== possibly lost: 88 bytes in 4 blocks ==18845== still reachable: 3,365 bytes in 31 blocks ==18845== suppressed: 0 bytes in 0 blocks ==18845== Rerun with --leak-check=full to see details of leaked memory ==18845== ==18845== For counts of detected and suppressed errors, rerun with: -v ==18845== ERROR SUMMARY: 111 errors from 9 contexts (suppressed: 0 from 0) Segmentation fault (core dumped)

up, until I try to implement dgemm matrix multiplication, I get no errors and no leaks, so I'm sure that all my problems are related to dgemm implementation

+4
source share
2 answers

The memory layout of version C is different from the memory layout in your C ++ version. Since BLAS expects the layout type used by version C, your C ++ version will not work.

Thus, you need to allocate a large one-dimensional array in your C ++ version; you can overload operator () to get indexing for 2D arrays. Or for production code, use a library such as Eigen .

+1
source

Sorry, I didn’t understand how to get into the game until the answer is sent.

I changed the indexing:

 double *data; data = new double[rows*columns];

then every time I want to index it, I just use the data [(i-1) * columns + (j-1)] to index the rows. The code definitely works now and compiles with 0 errors and 0 memory leaks! The only thing I get now is a completely shameless result.

Is this due to the fact that fortran is sorting by column while I am doing row-major? How to humble it?

0
source

Source: https://habr.com/ru/post/1444050/

More articles:


All Articles