NAME

dpptrs - 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 DPPTRF

SYNOPSIS

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

CHARACTER UPLO

INTEGER INFO, LDB, N, NRHS

DOUBLE PRECISION AP( ∗ ), B( LDB, ∗ )

#include <sunperf.h>

void dpptrs(char uplo, int n, int nrhs, double ∗dap, double ∗db, int ldb, int ∗info) ;

PURPOSE

DPPTRS 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 DPPTRF. 
 

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) DOUBLE PRECISION 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) DOUBLE PRECISION 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

SunOS 5.0  —  Last change: 10 Dec 1998