NAME

spptrs - solve 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

SYNOPSIS

SUBROUTINE SPPTRS(
UPLO, N, NRHS, AP, B, LDB, INFO )

CHARACTER UPLO

INTEGER INFO, LDB, N, NRHS

REAL AP( ∗ ), B( LDB, ∗ )

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

SunSoft, Inc.  —  Last change: 27 Jun 1995