# cqrt17.f - Man Page

TESTING/LIN/cqrt17.f

## Synopsis

### Functions/Subroutines

real function cqrt17 (trans, iresid, m, n, nrhs, a, lda, x, ldx, b, ldb, c, work, lwork)
CQRT17

## Function/Subroutine Documentation

### real function cqrt17 (character trans, integer iresid, integer m, integer n, integer nrhs, complex, dimension( lda, * ) a, integer lda, complex, dimension( ldx, * ) x, integer ldx, complex, dimension( ldb, * ) b, integer ldb, complex, dimension( ldb, * ) c, complex, dimension( lwork ) work, integer lwork)

CQRT17

Purpose:

``` CQRT17 computes the ratio

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

where R = B - op(A)*X, op(A) is A or A**H, 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.
= 'C':  Conjugate transpose, op(A) = A**H.```

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 = 'C', 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 = 'C', 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 COMPLEX 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 COMPLEX array, dimension (LDX,NRHS)
If TRANS = 'N', the n-by-nrhs matrix X.
If TRANS = 'C', the m-by-nrhs matrix X.```

LDX

```          LDX is INTEGER
The leading dimension of the array X.
If TRANS = 'N', LDX >= N.
If TRANS = 'C', LDX >= M.```

B

```          B is COMPLEX array, dimension (LDB,NRHS)
If TRANS = 'N', the m-by-nrhs matrix B.
If TRANS = 'C', the n-by-nrhs matrix B.```

LDB

```          LDB is INTEGER
The leading dimension of the array B.
If TRANS = 'N', LDB >= M.
If TRANS = 'C', LDB >= N.```

C

`          C is COMPLEX array, dimension (LDB,NRHS)`

WORK

`          WORK is COMPLEX 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 cqrt17.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page cqrt17(3) is an alias of cqrt17.f(3).

Tue Nov 28 2023 12:08:42 Version 3.12.0 LAPACK