#include "blaswrap.h" #include "f2c.h" /* Subroutine */ int zpbtrs_(char *uplo, integer *n, integer *kd, integer * nrhs, doublecomplex *ab, integer *ldab, doublecomplex *b, integer * ldb, integer *info) { /* -- LAPACK routine (version 3.1) -- Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. November 2006 Purpose ======= ZPBTRS solves a system of linear equations A*X = B with a Hermitian positive definite band matrix A using the Cholesky factorization A = U**H*U or A = L*L**H computed by ZPBTRF. Arguments ========= UPLO (input) CHARACTER*1 = 'U': Upper triangular factor stored in AB; = 'L': Lower triangular factor stored in AB. N (input) INTEGER The order of the matrix A. N >= 0. KD (input) INTEGER The number of superdiagonals of the matrix A if UPLO = 'U', or the number of subdiagonals if UPLO = 'L'. 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) COMPLEX*16 array, dimension (LDAB,N) The triangular factor U or L from the Cholesky factorization A = U**H*U or A = L*L**H of the band matrix A, stored in the first KD+1 rows of the array. The j-th column of U or L is stored in the j-th column of the array AB as follows: if UPLO ='U', AB(kd+1+i-j,j) = U(i,j) for max(1,j-kd)<=i<=j; if UPLO ='L', AB(1+i-j,j) = L(i,j) for j<=i<=min(n,j+kd). LDAB (input) INTEGER The leading dimension of the array AB. LDAB >= KD+1. B (input/output) COMPLEX*16 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; /* System generated locals */ integer ab_dim1, ab_offset, b_dim1, b_offset, i__1; /* Local variables */ static integer j; extern logical lsame_(char *, char *); static logical upper; extern /* Subroutine */ int ztbsv_(char *, char *, char *, integer *, integer *, doublecomplex *, integer *, doublecomplex *, integer *), xerbla_(char *, integer *); 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; upper = lsame_(uplo, "U"); if (! upper && ! lsame_(uplo, "L")) { *info = -1; } else if (*n < 0) { *info = -2; } else if (*kd < 0) { *info = -3; } else if (*nrhs < 0) { *info = -4; } else if (*ldab < *kd + 1) { *info = -6; } else if (*ldb < max(1,*n)) { *info = -8; } if (*info != 0) { i__1 = -(*info); xerbla_("ZPBTRS", &i__1); return 0; } /* Quick return if possible */ if (*n == 0 || *nrhs == 0) { return 0; } if (upper) { /* Solve A*X = B where A = U'*U. */ i__1 = *nrhs; for (j = 1; j <= i__1; ++j) { /* Solve U'*X = B, overwriting B with X. */ ztbsv_("Upper", "Conjugate transpose", "Non-unit", n, kd, &ab[ ab_offset], ldab, &b[j * b_dim1 + 1], &c__1); /* Solve U*X = B, overwriting B with X. */ ztbsv_("Upper", "No transpose", "Non-unit", n, kd, &ab[ab_offset], ldab, &b[j * b_dim1 + 1], &c__1); /* L10: */ } } else { /* Solve A*X = B where A = L*L'. */ i__1 = *nrhs; for (j = 1; j <= i__1; ++j) { /* Solve L*X = B, overwriting B with X. */ ztbsv_("Lower", "No transpose", "Non-unit", n, kd, &ab[ab_offset], ldab, &b[j * b_dim1 + 1], &c__1); /* Solve L'*X = B, overwriting B with X. */ ztbsv_("Lower", "Conjugate transpose", "Non-unit", n, kd, &ab[ ab_offset], ldab, &b[j * b_dim1 + 1], &c__1); /* L20: */ } } return 0; /* End of ZPBTRS */ } /* zpbtrs_ */