#include "blaswrap.h" #include "f2c.h" /* Subroutine */ int dgetrs_(char *trans, integer *n, integer *nrhs, doublereal *a, integer *lda, integer *ipiv, doublereal *b, integer * ldb, integer *info) { /* -- LAPACK routine (version 3.0) -- Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., Courant Institute, Argonne National Lab, and Rice University March 31, 1993 Purpose ======= DGETRS solves a system of linear equations A * X = B or A' * X = B with a general N-by-N matrix A using the LU factorization computed by DGETRF. Arguments ========= TRANS (input) CHARACTER*1 Specifies the form of the system of equations: = 'N': A * X = B (No transpose) = 'T': A'* X = B (Transpose) = 'C': A'* X = B (Conjugate transpose = Transpose) N (input) INTEGER The order of the matrix A. N >= 0. NRHS (input) INTEGER The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0. A (input) DOUBLE PRECISION array, dimension (LDA,N) The factors L and U from the factorization A = P*L*U as computed by DGETRF. LDA (input) INTEGER The leading dimension of the array A. LDA >= max(1,N). IPIV (input) INTEGER array, dimension (N) The pivot indices from DGETRF; for 1<=i<=N, row i of the matrix was interchanged with row IPIV(i). B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS) On entry, the right hand side matrix B. On exit, the solution matrix X. LDB (input) INTEGER The leading dimension of the array B. LDB >= max(1,N). INFO (output) INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value ===================================================================== Test the input parameters. Parameter adjustments */ /* Table of constant values */ static integer c__1 = 1; static doublereal c_b12 = 1.; static integer c_n1 = -1; /* System generated locals */ integer a_dim1, a_offset, b_dim1, b_offset, i__1; /* Local variables */ extern logical lsame_(char *, char *); extern /* Subroutine */ int dtrsm_(char *, char *, char *, char *, integer *, integer *, doublereal *, doublereal *, integer *, doublereal *, integer *), xerbla_( char *, integer *), dlaswp_(integer *, doublereal *, integer *, integer *, integer *, integer *, integer *); static logical notran; a_dim1 = *lda; a_offset = 1 + a_dim1 * 1; a -= a_offset; --ipiv; b_dim1 = *ldb; b_offset = 1 + b_dim1 * 1; b -= b_offset; /* Function Body */ *info = 0; notran = lsame_(trans, "N"); if (! notran && ! lsame_(trans, "T") && ! lsame_( trans, "C")) { *info = -1; } else if (*n < 0) { *info = -2; } else if (*nrhs < 0) { *info = -3; } else if (*lda < max(1,*n)) { *info = -5; } else if (*ldb < max(1,*n)) { *info = -8; } if (*info != 0) { i__1 = -(*info); xerbla_("DGETRS", &i__1); return 0; } /* Quick return if possible */ if (*n == 0 || *nrhs == 0) { return 0; } if (notran) { /* Solve A * X = B. Apply row interchanges to the right hand sides. */ dlaswp_(nrhs, &b[b_offset], ldb, &c__1, n, &ipiv[1], &c__1); /* Solve L*X = B, overwriting B with X. */ dtrsm_("Left", "Lower", "No transpose", "Unit", n, nrhs, &c_b12, &a[ a_offset], lda, &b[b_offset], ldb); /* Solve U*X = B, overwriting B with X. */ dtrsm_("Left", "Upper", "No transpose", "Non-unit", n, nrhs, &c_b12, & a[a_offset], lda, &b[b_offset], ldb); } else { /* Solve A' * X = B. Solve U'*X = B, overwriting B with X. */ dtrsm_("Left", "Upper", "Transpose", "Non-unit", n, nrhs, &c_b12, &a[ a_offset], lda, &b[b_offset], ldb); /* Solve L'*X = B, overwriting B with X. */ dtrsm_("Left", "Lower", "Transpose", "Unit", n, nrhs, &c_b12, &a[ a_offset], lda, &b[b_offset], ldb); /* Apply row interchanges to the solution vectors. */ dlaswp_(nrhs, &b[b_offset], ldb, &c__1, n, &ipiv[1], &c_n1); } return 0; /* End of DGETRS */ } /* dgetrs_ */