numeric-linalg
Educational material on the SciPy implementation of numerical linear algebra algorithms
| Name | Size | Mode | |
| .. | |||
| lapack/LAPACKE/example/example_DGESV_rowmajor.c | 3990B | -rw-r--r-- |
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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 (row-major, high-level) Example Program Results -- LAPACKE Example routine -- -- LAPACK is a software package provided by Univ. of Tennessee, -- -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- */ #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=nrhs; 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"); free(A); exit(0); } ipiv = (lapack_int *)malloc(n*sizeof(lapack_int)) ; if (ipiv==NULL){ printf("error of memory allocation\n"); free(A); free(b); exit(0); } for( i = 0; i < n; i++ ) { for( j = 0; j < n; j++ ) A[i*lda+j] = ((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_rowmajor( "Entry Matrix A", n, n, A, lda ); /* Print Right Rand Side */ print_matrix_rowmajor( "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_ROW_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(%" LAPACK_IFMT ",%" LAPACK_IFMT ") is zero, so that A is singular;\n", info, info ); printf( "the solution could not be computed.\n" ); free(A); free(b); free(ipiv); exit( 1 ); } if (info <0) { free(A); free(b); free(ipiv); exit( 1 ); } /* Print solution */ print_matrix_rowmajor( "Solution", n, nrhs, b, ldb ); /* Print details of LU factorization */ print_matrix_rowmajor( "Details of LU factorization", n, n, A, lda ); /* Print pivot indices */ print_vector( "Pivot indices", n, ipiv ); /* Free matrices and vectors */ free(A); free(b); free(ipiv); exit( 0 ); } /* End of LAPACKE_dgesv Example */