#include "blaswrap.h" #include "f2c.h" /* Subroutine */ int dtbtrs_(char *uplo, char *trans, char *diag, integer *n, integer *kd, integer *nrhs, doublereal *ab, integer *ldab, doublereal *b, integer *ldb, integer *info) { /* -- LAPACK routine (version 3.1) -- Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. November 2006 Purpose ======= DTBTRS solves a triangular system of the form A * X = B or A**T * X = B, where A is a triangular band 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 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. KD (input) INTEGER The number of superdiagonals or subdiagonals of the triangular band matrix A. KD >= 0. NRHS (input) INTEGER The number of right hand sides, i.e., the number of columns of the matrix B. NRHS >= 0. AB (input) DOUBLE PRECISION array, dimension (LDAB,N) The upper or lower triangular band matrix A, stored in the first kd+1 rows of AB. The j-th column of A is stored in the j-th column of the array AB as follows: if UPLO = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j; if UPLO = 'L', AB(1+i-j,j) = A(i,j) for j<=i<=min(n,j+kd). If DIAG = 'U', the diagonal elements of A are not referenced and are assumed to be 1. LDAB (input) INTEGER The leading dimension of the array AB. LDAB >= KD+1. 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. ===================================================================== Test the input parameters. Parameter adjustments */ /* Table of constant values */ static integer c__1 = 1; /* System generated locals */ integer ab_dim1, ab_offset, b_dim1, b_offset, i__1; /* Local variables */ static integer j; extern logical lsame_(char *, char *); extern /* Subroutine */ int dtbsv_(char *, char *, char *, integer *, integer *, doublereal *, integer *, doublereal *, integer *); static logical upper; extern /* Subroutine */ int xerbla_(char *, integer *); static logical nounit; ab_dim1 = *ldab; ab_offset = 1 + ab_dim1; ab -= ab_offset; b_dim1 = *ldb; b_offset = 1 + b_dim1; b -= b_offset; /* Function Body */ *info = 0; nounit = lsame_(diag, "N"); upper = lsame_(uplo, "U"); if (! upper && ! 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 (*kd < 0) { *info = -5; } else if (*nrhs < 0) { *info = -6; } else if (*ldab < *kd + 1) { *info = -8; } else if (*ldb < max(1,*n)) { *info = -10; } if (*info != 0) { i__1 = -(*info); xerbla_("DTBTRS", &i__1); return 0; } /* Quick return if possible */ if (*n == 0) { return 0; } /* Check for singularity. */ if (nounit) { if (upper) { i__1 = *n; for (*info = 1; *info <= i__1; ++(*info)) { if (ab[*kd + 1 + *info * ab_dim1] == 0.) { return 0; } /* L10: */ } } else { i__1 = *n; for (*info = 1; *info <= i__1; ++(*info)) { if (ab[*info * ab_dim1 + 1] == 0.) { return 0; } /* L20: */ } } } *info = 0; /* Solve A * X = B or A' * X = B. */ i__1 = *nrhs; for (j = 1; j <= i__1; ++j) { dtbsv_(uplo, trans, diag, n, kd, &ab[ab_offset], ldab, &b[j * b_dim1 + 1], &c__1); /* L30: */ } return 0; /* End of DTBTRS */ } /* dtbtrs_ */