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/*
LAPACKE_dgesv Example
=====================
The program computes the solution to the system of linear
equations with a square matrix A and multiple
right-hand sides B, where A is the coefficient matrix
and b is the right-hand side matrix:
Description
===========
The routine solves for X the system of linear equations A*X = B,
where A is an n-by-n matrix, the columns of matrix B are individual
right-hand sides, and the columns of X are the corresponding
solutions.
The LU decomposition with partial pivoting and row interchanges is
used to factor A as A = P*L*U, where P is a permutation matrix, L
is unit lower triangular, and U is upper triangular. The factored
form of A is then used to solve the system of equations A*X = B.
LAPACKE Interface
=================
LAPACKE_dgesv (col-major, high-level) Example Program Results
-- LAPACKE Example routine (version 3.6.0) --
-- LAPACK is a software package provided by Univ. of Tennessee, --
-- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
November 2015
*/
/* Includes */
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "lapacke.h"
#include "lapacke_example_aux.h"
/* Main program */
int main(int argc, char **argv) {
/* Locals */
lapack_int n, nrhs, lda, ldb, info;
int i, j;
/* Local arrays */
double *A, *b;
lapack_int *ipiv;
/* Default Value */
n = 5; nrhs = 1;
/* Arguments */
for( i = 1; i < argc; i++ ) {
if( strcmp( argv[i], "-n" ) == 0 ) {
n = atoi(argv[i+1]);
i++;
}
if( strcmp( argv[i], "-nrhs" ) == 0 ) {
nrhs = atoi(argv[i+1]);
i++;
}
}
/* Initialization */
lda=n, ldb=n;
A = (double *)malloc(n*n*sizeof(double)) ;
if (A==NULL){ printf("error of memory allocation\n"); exit(0); }
b = (double *)malloc(n*nrhs*sizeof(double)) ;
if (b==NULL){ printf("error of memory allocation\n"); exit(0); }
ipiv = (lapack_int *)malloc(n*sizeof(lapack_int)) ;
if (ipiv==NULL){ printf("error of memory allocation\n"); exit(0); }
for( i = 0; i < n; i++ ) {
for( j = 0; j < n; j++ ) A[i+j*lda] = ((double) rand()) / ((double) RAND_MAX) - 0.5;
}
for(i=0;i<n*nrhs;i++)
b[i] = ((double) rand()) / ((double) RAND_MAX) - 0.5;
/* Print Entry Matrix */
print_matrix_colmajor( "Entry Matrix A", n, n, A, lda );
/* Print Right Rand Side */
print_matrix_colmajor( "Right Rand Side b", n, nrhs, b, ldb );
printf( "\n" );
/* Executable statements */
printf( "LAPACKE_dgesv (row-major, high-level) Example Program Results\n" );
/* Solve the equations A*X = B */
info = LAPACKE_dgesv( LAPACK_COL_MAJOR, n, nrhs, A, lda, ipiv,
b, ldb );
/* Check for the exact singularity */
if( info > 0 ) {
printf( "The diagonal element of the triangular factor of A,\n" );
printf( "U(%i,%i) is zero, so that A is singular;\n", info, info );
printf( "the solution could not be computed.\n" );
exit( 1 );
}
if (info <0) exit( 1 );
/* Print solution */
print_matrix_colmajor( "Solution", n, nrhs, b, ldb );
/* Print details of LU factorization */
print_matrix_colmajor( "Details of LU factorization", n, n, A, lda );
/* Print pivot indices */
print_vector( "Pivot indices", n, ipiv );
exit( 0 );
} /* End of LAPACKE_dgesv Example */
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