---
name: "sqrt17.f"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/sqrt17.f"
---

# sqrt17.f(3)

## NAME

TESTING/LIN/sqrt17.f

## SYNOPSIS

### Functions/Subroutines

real function **sqrt17** (trans, iresid, m, n, nrhs, a, lda, x, ldx, b, ldb, c, work, lwork)\
 **SQRT17**

## Function/Subroutine Documentation

### real function sqrt17 (character trans, integer iresid, integer m, integer n, integer nrhs, real, dimension( lda, \* ) a, integer lda, real, dimension( ldx, \* ) x, integer ldx, real, dimension( ldb, \* ) b, integer ldb, real, dimension( ldb, \* ) c, real, dimension( lwork ) work, integer lwork)

**SQRT17**

**Purpose:**

```
!>
!> SQRT17 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 REAL 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 REAL 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 REAL 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 REAL array, dimension (LDB,NRHS)
!>
```

*WORK*

```
!>          WORK is REAL 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

Univ. of Colorado Denver

NAG Ltd.

Definition at line **151** of file **sqrt17.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.