DSPTRS - solve a system of linear equations A*X = B with a
real symmetric matrix A stored in packed format using the
factorization A = U*D*U**T or A = L*D*L**T computed by
DSPTRF
SYNOPSIS
SUBROUTINE DSPTRS( UPLO, N, NRHS, AP, IPIV, B, LDB, INFO )
CHARACTER UPLO
INTEGER INFO, LDB, N, NRHS
INTEGER IPIV( * )
DOUBLE PRECISION AP( * ), B( LDB, * )
PURPOSE
DSPTRS solves a system of linear equations A*X = B with a
real symmetric matrix A stored in packed format using the
factorization A = U*D*U**T or A = L*D*L**T computed by
DSPTRF.
ARGUMENTS
UPLO (input) CHARACTER*1
Specifies whether the details of the factorization
are stored as an upper or lower triangular matrix.
= 'U': Upper triangular, form is A = U*D*U**T;
= 'L': Lower triangular, form is A = L*D*L**T.
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 block diagonal matrix D and the multipliers
used to obtain the factor U or L as computed by
DSPTRF, stored as a packed triangular matrix.
IPIV (input) INTEGER array, dimension (N)
Details of the interchanges and the block struc
ture of D as determined by DSPTRF.
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 >=
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille
gal value
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