#include "blaswrap.h" #include "f2c.h" /* Subroutine */ int dpttrs_(integer *n, integer *nrhs, doublereal *d__, doublereal *e, doublereal *b, integer *ldb, integer *info) { /* -- LAPACK routine (version 3.1) -- Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. November 2006 Purpose ======= DPTTRS solves a tridiagonal system of the form A * X = B using the L*D*L' factorization of A computed by DPTTRF. D is a diagonal matrix specified in the vector D, L is a unit bidiagonal matrix whose subdiagonal is specified in the vector E, and X and B are N by NRHS matrices. Arguments ========= N (input) INTEGER The order of the tridiagonal 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. D (input) DOUBLE PRECISION array, dimension (N) The n diagonal elements of the diagonal matrix D from the L*D*L' factorization of A. E (input) DOUBLE PRECISION array, dimension (N-1) The (n-1) subdiagonal elements of the unit bidiagonal factor L from the L*D*L' factorization of A. E can also be regarded as the superdiagonal of the unit bidiagonal factor U from the factorization A = U'*D*U. B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS) On entry, the right hand side vectors B for the system of linear equations. On exit, the solution vectors, X. LDB (input) INTEGER The leading dimension of the array B. LDB >= max(1,N). INFO (output) INTEGER = 0: successful exit < 0: if INFO = -k, the k-th argument had an illegal value ===================================================================== Test the input arguments. Parameter adjustments */ /* Table of constant values */ static integer c__1 = 1; static integer c_n1 = -1; /* System generated locals */ integer b_dim1, b_offset, i__1, i__2, i__3; /* Local variables */ static integer j, jb, nb; extern /* Subroutine */ int dptts2_(integer *, integer *, doublereal *, doublereal *, doublereal *, integer *), xerbla_(char *, integer *); extern integer ilaenv_(integer *, char *, char *, integer *, integer *, integer *, integer *, ftnlen, ftnlen); --d__; --e; b_dim1 = *ldb; b_offset = 1 + b_dim1; b -= b_offset; /* Function Body */ *info = 0; if (*n < 0) { *info = -1; } else if (*nrhs < 0) { *info = -2; } else if (*ldb < max(1,*n)) { *info = -6; } if (*info != 0) { i__1 = -(*info); xerbla_("DPTTRS", &i__1); return 0; } /* Quick return if possible */ if (*n == 0 || *nrhs == 0) { return 0; } /* Determine the number of right-hand sides to solve at a time. */ if (*nrhs == 1) { nb = 1; } else { /* Computing MAX */ i__1 = 1, i__2 = ilaenv_(&c__1, "DPTTRS", " ", n, nrhs, &c_n1, &c_n1, (ftnlen)6, (ftnlen)1); nb = max(i__1,i__2); } if (nb >= *nrhs) { dptts2_(n, nrhs, &d__[1], &e[1], &b[b_offset], ldb); } else { i__1 = *nrhs; i__2 = nb; for (j = 1; i__2 < 0 ? j >= i__1 : j <= i__1; j += i__2) { /* Computing MIN */ i__3 = *nrhs - j + 1; jb = min(i__3,nb); dptts2_(n, &jb, &d__[1], &e[1], &b[j * b_dim1 + 1], ldb); /* L10: */ } } return 0; /* End of DPTTRS */ } /* dpttrs_ */