#include "blaswrap.h" #include "f2c.h" /* Subroutine */ int sptsv_(integer *n, integer *nrhs, real *d__, real *e, real *b, integer *ldb, integer *info) { /* -- LAPACK routine (version 3.1) -- Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. November 2006 Purpose ======= SPTSV computes the solution to a real system of linear equations A*X = B, where A is an N-by-N symmetric positive definite tridiagonal matrix, and X and B are N-by-NRHS matrices. A is factored as A = L*D*L**T, and the factored form of A is then used to solve the system of equations. Arguments ========= 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. D (input/output) REAL array, dimension (N) On entry, the n diagonal elements of the tridiagonal matrix A. On exit, the n diagonal elements of the diagonal matrix D from the factorization A = L*D*L**T. E (input/output) REAL array, dimension (N-1) On entry, the (n-1) subdiagonal elements of the tridiagonal matrix A. On exit, the (n-1) subdiagonal elements of the unit bidiagonal factor L from the L*D*L**T factorization of A. (E can also be regarded as the superdiagonal of the unit bidiagonal factor U from the U**T*D*U factorization of A.) B (input/output) REAL array, dimension (LDB,NRHS) On entry, the N-by-NRHS right hand side matrix B. On exit, if INFO = 0, the N-by-NRHS 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 leading minor of order i is not positive definite, and the solution has not been computed. The factorization has not been completed unless i = N. ===================================================================== Test the input parameters. Parameter adjustments */ /* System generated locals */ integer b_dim1, b_offset, i__1; /* Local variables */ extern /* Subroutine */ int xerbla_(char *, integer *), spttrf_( integer *, real *, real *, integer *), spttrs_(integer *, integer *, real *, real *, real *, integer *, integer *); --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_("SPTSV ", &i__1); return 0; } /* Compute the L*D*L' (or U'*D*U) factorization of A. */ spttrf_(n, &d__[1], &e[1], info); if (*info == 0) { /* Solve the system A*X = B, overwriting B with X. */ spttrs_(n, nrhs, &d__[1], &e[1], &b[b_offset], ldb, info); } return 0; /* End of SPTSV */ } /* sptsv_ */