#include "blaswrap.h" #include "f2c.h" /* Subroutine */ int spptrs_(char *uplo, integer *n, integer *nrhs, real *ap, real *b, integer *ldb, integer *info) { /* -- LAPACK routine (version 3.1) -- Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. November 2006 Purpose ======= SPPTRS solves a system of linear equations A*X = B with a symmetric positive definite matrix A in packed storage using the Cholesky factorization A = U**T*U or A = L*L**T computed by SPPTRF. Arguments ========= UPLO (input) CHARACTER*1 = 'U': Upper triangle of A is stored; = 'L': Lower triangle of A is stored. 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. AP (input) REAL array, dimension (N*(N+1)/2) The triangular factor U or L from the Cholesky factorization A = U**T*U or A = L*L**T, packed columnwise in a linear array. The j-th column of U or L is stored in the array AP as follows: if UPLO = 'U', AP(i + (j-1)*j/2) = U(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = L(i,j) for j<=i<=n. B (input/output) REAL 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 b_dim1, b_offset, i__1; /* Local variables */ static integer i__; extern logical lsame_(char *, char *); static logical upper; extern /* Subroutine */ int stpsv_(char *, char *, char *, integer *, real *, real *, integer *), xerbla_(char * , integer *); --ap; 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 (*nrhs < 0) { *info = -3; } else if (*ldb < max(1,*n)) { *info = -6; } if (*info != 0) { i__1 = -(*info); xerbla_("SPPTRS", &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 (i__ = 1; i__ <= i__1; ++i__) { /* Solve U'*X = B, overwriting B with X. */ stpsv_("Upper", "Transpose", "Non-unit", n, &ap[1], &b[i__ * b_dim1 + 1], &c__1); /* Solve U*X = B, overwriting B with X. */ stpsv_("Upper", "No transpose", "Non-unit", n, &ap[1], &b[i__ * b_dim1 + 1], &c__1); /* L10: */ } } else { /* Solve A*X = B where A = L*L'. */ i__1 = *nrhs; for (i__ = 1; i__ <= i__1; ++i__) { /* Solve L*Y = B, overwriting B with X. */ stpsv_("Lower", "No transpose", "Non-unit", n, &ap[1], &b[i__ * b_dim1 + 1], &c__1); /* Solve L'*X = Y, overwriting B with X. */ stpsv_("Lower", "Transpose", "Non-unit", n, &ap[1], &b[i__ * b_dim1 + 1], &c__1); /* L20: */ } } return 0; /* End of SPPTRS */ } /* spptrs_ */