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