rpl/lapack/lapack/dgesv.f - view

File: [local] / rpl / lapack / lapack / dgesv.f
Revision 1.17: download - view: text, annotated - select for diffs - revision graph
Mon Aug 7 08:38:50 2023 UTC (8 months, 3 weeks ago) by bertrand
Branches: MAIN
CVS tags: rpl-4_1_35, rpl-4_1_34, HEAD

Première mise à jour de lapack et blas.

1: *> \brief <b> DGESV computes the solution to system of linear equations A * X = B for GE matrices</b> 2: * 3: * =========== DOCUMENTATION =========== 4: * 5: * Online html documentation available at 6: * http://www.netlib.org/lapack/explore-html/ 7: * 8: *> \htmlonly 9: *> Download DGESV + dependencies 10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dgesv.f"> 11: *> [TGZ]</a> 12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dgesv.f"> 13: *> [ZIP]</a> 14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dgesv.f"> 15: *> [TXT]</a> 16: *> \endhtmlonly 17: * 18: * Definition: 19: * =========== 20: * 21: * SUBROUTINE DGESV( N, NRHS, A, LDA, IPIV, B, LDB, INFO ) 22: * 23: * .. Scalar Arguments .. 24: * INTEGER INFO, LDA, LDB, N, NRHS 25: * .. 26: * .. Array Arguments .. 27: * INTEGER IPIV( * ) 28: * DOUBLE PRECISION A( LDA, * ), B( LDB, * ) 29: * .. 30: * 31: * 32: *> \par Purpose: 33: * ============= 34: *> 35: *> \verbatim 36: *> 37: *> DGESV computes the solution to a real system of linear equations 38: *> A * X = B, 39: *> where A is an N-by-N matrix and X and B are N-by-NRHS matrices. 40: *> 41: *> The LU decomposition with partial pivoting and row interchanges is 42: *> used to factor A as 43: *> A = P * L * U, 44: *> where P is a permutation matrix, L is unit lower triangular, and U is 45: *> upper triangular. The factored form of A is then used to solve the 46: *> system of equations A * X = B. 47: *> \endverbatim 48: * 49: * Arguments: 50: * ========== 51: * 52: *> \param[in] N 53: *> \verbatim 54: *> N is INTEGER 55: *> The number of linear equations, i.e., the order of the 56: *> matrix A. N >= 0. 57: *> \endverbatim 58: *> 59: *> \param[in] NRHS 60: *> \verbatim 61: *> NRHS is INTEGER 62: *> The number of right hand sides, i.e., the number of columns 63: *> of the matrix B. NRHS >= 0. 64: *> \endverbatim 65: *> 66: *> \param[in,out] A 67: *> \verbatim 68: *> A is DOUBLE PRECISION array, dimension (LDA,N) 69: *> On entry, the N-by-N coefficient matrix A. 70: *> On exit, the factors L and U from the factorization 71: *> A = P*L*U; the unit diagonal elements of L are not stored. 72: *> \endverbatim 73: *> 74: *> \param[in] LDA 75: *> \verbatim 76: *> LDA is INTEGER 77: *> The leading dimension of the array A. LDA >= max(1,N). 78: *> \endverbatim 79: *> 80: *> \param[out] IPIV 81: *> \verbatim 82: *> IPIV is INTEGER array, dimension (N) 83: *> The pivot indices that define the permutation matrix P; 84: *> row i of the matrix was interchanged with row IPIV(i). 85: *> \endverbatim 86: *> 87: *> \param[in,out] B 88: *> \verbatim 89: *> B is DOUBLE PRECISION array, dimension (LDB,NRHS) 90: *> On entry, the N-by-NRHS matrix of right hand side matrix B. 91: *> On exit, if INFO = 0, the N-by-NRHS solution matrix X. 92: *> \endverbatim 93: *> 94: *> \param[in] LDB 95: *> \verbatim 96: *> LDB is INTEGER 97: *> The leading dimension of the array B. LDB >= max(1,N). 98: *> \endverbatim 99: *> 100: *> \param[out] INFO 101: *> \verbatim 102: *> INFO is INTEGER 103: *> = 0: successful exit 104: *> < 0: if INFO = -i, the i-th argument had an illegal value 105: *> > 0: if INFO = i, U(i,i) is exactly zero. The factorization 106: *> has been completed, but the factor U is exactly 107: *> singular, so the solution could not be computed. 108: *> \endverbatim 109: * 110: * Authors: 111: * ======== 112: * 113: *> \author Univ. of Tennessee 114: *> \author Univ. of California Berkeley 115: *> \author Univ. of Colorado Denver 116: *> \author NAG Ltd. 117: * 118: *> \ingroup doubleGEsolve 119: * 120: * ===================================================================== 121: SUBROUTINE DGESV( N, NRHS, A, LDA, IPIV, B, LDB, INFO ) 122: * 123: * -- LAPACK driver routine -- 124: * -- LAPACK is a software package provided by Univ. of Tennessee, -- 125: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- 126: * 127: * .. Scalar Arguments .. 128: INTEGER INFO, LDA, LDB, N, NRHS 129: * .. 130: * .. Array Arguments .. 131: INTEGER IPIV( * ) 132: DOUBLE PRECISION A( LDA, * ), B( LDB, * ) 133: * .. 134: * 135: * ===================================================================== 136: * 137: * .. External Subroutines .. 138: EXTERNAL DGETRF, DGETRS, XERBLA 139: * .. 140: * .. Intrinsic Functions .. 141: INTRINSIC MAX 142: * .. 143: * .. Executable Statements .. 144: * 145: * Test the input parameters. 146: * 147: INFO = 0 148: IF( N.LT.0 ) THEN 149: INFO = -1 150: ELSE IF( NRHS.LT.0 ) THEN 151: INFO = -2 152: ELSE IF( LDA.LT.MAX( 1, N ) ) THEN 153: INFO = -4 154: ELSE IF( LDB.LT.MAX( 1, N ) ) THEN 155: INFO = -7 156: END IF 157: IF( INFO.NE.0 ) THEN 158: CALL XERBLA( 'DGESV ', -INFO ) 159: RETURN 160: END IF 161: * 162: * Compute the LU factorization of A. 163: * 164: CALL DGETRF( N, N, A, LDA, IPIV, INFO ) 165: IF( INFO.EQ.0 ) THEN 166: * 167: * Solve the system A*X = B, overwriting B with X. 168: * 169: CALL DGETRS( 'No transpose', N, NRHS, A, LDA, IPIV, B, LDB, 170: $ INFO ) 171: END IF 172: RETURN 173: * 174: * End of DGESV 175: * 176: END