#include "clapack.h" /* Table of constant values */ static doublereal c_b12 = 1.; /* Subroutine */ int dtrtrs_(char *uplo, char *trans, char *diag, integer *n, integer *nrhs, doublereal *a, integer *lda, doublereal *b, integer * ldb, integer *info) { /* 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 *); logical nounit; /* -- LAPACK routine (version 3.1) -- */ /* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */ /* November 2006 */ /* .. Scalar Arguments .. */ /* .. */ /* .. Array Arguments .. */ /* .. */ /* Purpose */ /* ======= */ /* DTRTRS solves a triangular system of the form */ /* A * X = B or A**T * X = B, */ /* where A is a triangular matrix of order N, and B is an N-by-NRHS */ /* matrix. A check is made to verify that A is nonsingular. */ /* Arguments */ /* ========= */ /* UPLO (input) CHARACTER*1 */ /* = 'U': A is upper triangular; */ /* = 'L': A is lower triangular. */ /* TRANS (input) CHARACTER*1 */ /* Specifies the form of the system of equations: */ /* = 'N': A * X = B (No transpose) */ /* = 'T': A**T * X = B (Transpose) */ /* = 'C': A**H * X = B (Conjugate transpose = Transpose) */ /* DIAG (input) CHARACTER*1 */ /* = 'N': A is non-unit triangular; */ /* = 'U': A is unit triangular. */ /* 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 triangular matrix A. If UPLO = 'U', the leading N-by-N */ /* upper triangular part of the array A contains the upper */ /* triangular matrix, and the strictly lower triangular part of */ /* A is not referenced. If UPLO = 'L', the leading N-by-N lower */ /* triangular part of the array A contains the lower triangular */ /* matrix, and the strictly upper triangular part of A is not */ /* referenced. If DIAG = 'U', the diagonal elements of A are */ /* also not referenced and are assumed to be 1. */ /* LDA (input) INTEGER */ /* The leading dimension of the array A. LDA >= max(1,N). */ /* B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS) */ /* On entry, the right hand side matrix B. */ /* On exit, if INFO = 0, 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 */ /* > 0: if INFO = i, the i-th diagonal element of A is zero, */ /* indicating that the matrix is singular and the solutions */ /* X have not been computed. */ /* ===================================================================== */ /* .. Parameters .. */ /* .. */ /* .. Local Scalars .. */ /* .. */ /* .. External Functions .. */ /* .. */ /* .. External Subroutines .. */ /* .. */ /* .. Intrinsic Functions .. */ /* .. */ /* .. Executable Statements .. */ /* Test the input parameters. */ /* Parameter adjustments */ a_dim1 = *lda; a_offset = 1 + a_dim1; a -= a_offset; b_dim1 = *ldb; b_offset = 1 + b_dim1; b -= b_offset; /* Function Body */ *info = 0; nounit = lsame_(diag, "N"); if (! lsame_(uplo, "U") && ! lsame_(uplo, "L")) { *info = -1; } else if (! lsame_(trans, "N") && ! lsame_(trans, "T") && ! lsame_(trans, "C")) { *info = -2; } else if (! nounit && ! lsame_(diag, "U")) { *info = -3; } else if (*n < 0) { *info = -4; } else if (*nrhs < 0) { *info = -5; } else if (*lda < max(1,*n)) { *info = -7; } else if (*ldb < max(1,*n)) { *info = -9; } if (*info != 0) { i__1 = -(*info); xerbla_("DTRTRS", &i__1); return 0; } /* Quick return if possible */ if (*n == 0) { return 0; } /* Check for singularity. */ if (nounit) { i__1 = *n; for (*info = 1; *info <= i__1; ++(*info)) { if (a[*info + *info * a_dim1] == 0.) { return 0; } /* L10: */ } } *info = 0; /* Solve A * x = b or A' * x = b. */ dtrsm_("Left", uplo, trans, diag, n, nrhs, &c_b12, &a[a_offset], lda, &b[ b_offset], ldb); return 0; /* End of DTRTRS */ } /* dtrtrs_ */