DSPTRS (3lapack)

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 structure 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 >= max(1,N).

  INFO    (output) INTEGER
          = 0:  successful exit
          < 0: if INFO = -i, the i-th argument had an illegal value