dqrt17.f - Man Page

TESTING/LIN/dqrt17.f

Synopsis

Functions/Subroutines

double precision function dqrt17 (trans, iresid, m, n, nrhs, a, lda, x, ldx, b, ldb, c, work, lwork)
DQRT17

Function/Subroutine Documentation

double precision function dqrt17 (character trans, integer iresid, integer m, integer n, integer nrhs, double precision, dimension( lda, * ) a, integer lda, double precision, dimension( ldx, * ) x, integer ldx, double precision, dimension( ldb, * ) b, integer ldb, double precision, dimension( ldb, * ) c, double precision, dimension( lwork ) work, integer lwork)

DQRT17

Purpose:

``` DQRT17 computes the ratio

norm(R**T * op(A)) / ( norm(A) * alpha * max(M,N,NRHS) * EPS ),

where R = B - op(A)*X, op(A) is A or A**T, depending on TRANS, EPS
is the machine epsilon, and

alpha = norm(B) if IRESID = 1 (zero-residual problem)
alpha = norm(R) if IRESID = 2 (otherwise).

The norm used is the 1-norm.```
Parameters

TRANS

```          TRANS is CHARACTER*1
Specifies whether or not the transpose of A is used.
= 'N':  No transpose, op(A) = A.
= 'T':  Transpose, op(A) = A**T.```

IRESID

```          IRESID is INTEGER
IRESID = 1 indicates zero-residual problem.
IRESID = 2 indicates non-zero residual.```

M

```          M is INTEGER
The number of rows of the matrix A.
If TRANS = 'N', the number of rows of the matrix B.
If TRANS = 'T', the number of rows of the matrix X.```

N

```          N is INTEGER
The number of columns of the matrix  A.
If TRANS = 'N', the number of rows of the matrix X.
If TRANS = 'T', the number of rows of the matrix B.```

NRHS

```          NRHS is INTEGER
The number of columns of the matrices X and B.```

A

```          A is DOUBLE PRECISION array, dimension (LDA,N)
The m-by-n matrix A.```

LDA

```          LDA is INTEGER
The leading dimension of the array A. LDA >= M.```

X

```          X is DOUBLE PRECISION array, dimension (LDX,NRHS)
If TRANS = 'N', the n-by-nrhs matrix X.
If TRANS = 'T', the m-by-nrhs matrix X.```

LDX

```          LDX is INTEGER
The leading dimension of the array X.
If TRANS = 'N', LDX >= N.
If TRANS = 'T', LDX >= M.```

B

```          B is DOUBLE PRECISION array, dimension (LDB,NRHS)
If TRANS = 'N', the m-by-nrhs matrix B.
If TRANS = 'T', the n-by-nrhs matrix B.```

LDB

```          LDB is INTEGER
The leading dimension of the array B.
If TRANS = 'N', LDB >= M.
If TRANS = 'T', LDB >= N.```

C

`          C is DOUBLE PRECISION array, dimension (LDB,NRHS)`

WORK

`          WORK is DOUBLE PRECISION array, dimension (LWORK)`

LWORK

```          LWORK is INTEGER
The length of the array WORK.  LWORK >= NRHS*(M+N).```
Author

Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Definition at line 151 of file dqrt17.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

The man page dqrt17(3) is an alias of dqrt17.f(3).

Tue Nov 28 2023 12:08:43 Version 3.12.0 LAPACK