SSYTRS2 solves a system of linear equations A*X = B with a real


 symmetric matrix A using the factorization A = U*D*U**T or


 A = L*D*L**T computed by SSYTRF and converted by SSYCONV.

UPLO

          UPLO is 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

          N is INTEGER


          The order of the matrix A.  N >= 0.

NRHS

          NRHS is INTEGER


          The number of right hand sides, i.e., the number of columns


          of the matrix B.  NRHS >= 0.

A

          A is REAL array, dimension (LDA,N)


          The block diagonal matrix D and the multipliers used to


          obtain the factor U or L as computed by SSYTRF.


          Note that A is input / output. This might be counter-intuitive,


          and one may think that A is input only. A is input / output. This


          is because, at the start of the subroutine, we permute A in a


          "better" form and then we permute A back to its original form at


          the end.

LDA

          LDA is INTEGER


          The leading dimension of the array A.  LDA >= max(1,N).

IPIV

          IPIV is INTEGER array, dimension (N)


          Details of the interchanges and the block structure of D


          as determined by SSYTRF.

B

          B is REAL array, dimension (LDB,NRHS)


          On entry, the right hand side matrix B.


          On exit, the solution matrix X.

LDB

          LDB is INTEGER


          The leading dimension of the array B.  LDB >= max(1,N).

WORK

          WORK is REAL array, dimension (N)

INFO

          INFO is INTEGER


          = 0:  successful exit


          < 0:  if INFO = -i, the i-th argument had an illegal value

Univ. of Tennessee

Univ. of California Berkeley

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NAG Ltd.

December 2016