# dsytrs_aa_2stage.f

Section: LAPACK (3)
Updated: Tue Nov 14 2017
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## NAME

dsytrs_aa_2stage.f

## SYNOPSIS

### Functions/Subroutines

subroutine dsytrs_aa_2stage (UPLO, N, NRHS, A, LDA, TB, LTB, IPIV, IPIV2, B, LDB, INFO)
DSYTRS_AA_2STAGE

## Function/Subroutine Documentation

### subroutine dsytrs_aa_2stage (character UPLO, integer N, integer NRHS, double precision, dimension( lda, * ) A, integer LDA, double precision, dimension( * ) TB, integer LTB, integer, dimension( * ) IPIV, integer, dimension( * ) IPIV2, double precision, dimension( ldb, * ) B, integer LDB, integer INFO)

DSYTRS_AA_2STAGE

Purpose:

``` DSYTRS_AA_2STAGE solves a system of linear equations A*X = B with a real
symmetric matrix A using the factorization A = U*T*U**T or
A = L*T*L**T computed by DSYTRF_AA_2STAGE.
```

Parameters:

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*T*U**T;
= 'L':  Lower triangular, form is A = L*T*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 DOUBLE PRECISION array, dimension (LDA,N)
Details of factors computed by DSYTRF_AA_2STAGE.
```

LDA

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

TB

```          TB is DOUBLE PRECISION array, dimension (LTB)
Details of factors computed by DSYTRF_AA_2STAGE.
```

LTB

```          The size of the array TB. LTB >= 4*N.
```

IPIV

```          IPIV is INTEGER array, dimension (N)
Details of the interchanges as computed by
DSYTRF_AA_2STAGE.
```

IPIV2

```          IPIV2 is INTEGER array, dimension (N)
Details of the interchanges as computed by
DSYTRF_AA_2STAGE.
```

B

```          B is DOUBLE PRECISION 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).
```

INFO

```          INFO is INTEGER
= 0:  successful exit
< 0:  if INFO = -i, the i-th argument had an illegal value
```

Author:

Univ. of Tennessee

Univ. of California Berkeley