---
name: "slarhs.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/slarhs.f"
---

# slarhs.f(3)

## NAME

TESTING/LIN/slarhs.f

## SYNOPSIS

### Functions/Subroutines

subroutine **slarhs** (path, xtype, uplo, trans, m, n, kl, ku, nrhs, a, lda, x, ldx, b, ldb, iseed, info)\
 **SLARHS**

## Function/Subroutine Documentation

### subroutine slarhs (character\*3 path, character xtype, character uplo, character trans, integer m, integer n, integer kl, integer ku, integer nrhs, real, dimension( lda, \* ) a, integer lda, real, dimension( ldx, \* ) x, integer ldx, real, dimension( ldb, \* ) b, integer ldb, integer, dimension( 4 ) iseed, integer info)

**SLARHS**

**Purpose:**

```
!>
!> SLARHS chooses a set of NRHS random solution vectors and sets
!> up the right hand sides for the linear system
!>    op(A) * X = B,
!> where op(A) = A or A**T, depending on TRANS.
!>
```

**Parameters**

*PATH*

```
!>          PATH is CHARACTER*3
!>          The type of the real matrix A.  PATH may be given in any
!>          combination of upper and lower case.  Valid types include
!>             xGE:  General m x n matrix
!>             xGB:  General banded matrix
!>             xPO:  Symmetric positive definite, 2-D storage
!>             xPP:  Symmetric positive definite packed
!>             xPB:  Symmetric positive definite banded
!>             xSY:  Symmetric indefinite, 2-D storage
!>             xSP:  Symmetric indefinite packed
!>             xSB:  Symmetric indefinite banded
!>             xTR:  Triangular
!>             xTP:  Triangular packed
!>             xTB:  Triangular banded
!>             xQR:  General m x n matrix
!>             xLQ:  General m x n matrix
!>             xQL:  General m x n matrix
!>             xRQ:  General m x n matrix
!>          where the leading character indicates the precision.
!>
```

*XTYPE*

```
!>          XTYPE is CHARACTER*1
!>          Specifies how the exact solution X will be determined:
!>          = 'N':  New solution; generate a random X.
!>          = 'C':  Computed; use value of X on entry.
!>
```

*UPLO*

```
!>          UPLO is CHARACTER*1
!>          Specifies whether the upper or lower triangular part of the
!>          matrix A is stored, if A is symmetric.
!>          = 'U':  Upper triangular
!>          = 'L':  Lower triangular
!>
```

*TRANS*

```
!>          TRANS is CHARACTER*1
!>          Used only if A is nonsymmetric; specifies the operation
!>          applied to the matrix A.
!>          = 'N':  B := A    * X  (No transpose)
!>          = 'T':  B := A**T * X  (Transpose)
!>          = 'C':  B := A**H * X  (Conjugate transpose = Transpose)
!>
```

*M*

```
!>          M is INTEGER
!>          The number or rows of the matrix A.  M >= 0.
!>
```

*N*

```
!>          N is INTEGER
!>          The number of columns of the matrix A.  N >= 0.
!>
```

*KL*

```
!>          KL is INTEGER
!>          Used only if A is a band matrix; specifies the number of
!>          subdiagonals of A if A is a general band matrix or if A is
!>          symmetric or triangular and UPLO = 'L'; specifies the number
!>          of superdiagonals of A if A is symmetric or triangular and
!>          UPLO = 'U'.  0 <= KL <= M-1.
!>
```

*KU*

```
!>          KU is INTEGER
!>          Used only if A is a general band matrix or if A is
!>          triangular.
!>
!>          If PATH = xGB, specifies the number of superdiagonals of A,
!>          and 0 <= KU <= N-1.
!>
!>          If PATH = xTR, xTP, or xTB, specifies whether or not the
!>          matrix has unit diagonal:
!>          = 1:  matrix has non-unit diagonal (default)
!>          = 2:  matrix has unit diagonal
!>
```

*NRHS*

```
!>          NRHS is INTEGER
!>          The number of right hand side vectors in the system A*X = B.
!>
```

*A*

```
!>          A is REAL array, dimension (LDA,N)
!>          The test matrix whose type is given by PATH.
!>
```

*LDA*

```
!>          LDA is INTEGER
!>          The leading dimension of the array A.
!>          If PATH = xGB, LDA >= KL+KU+1.
!>          If PATH = xPB, xSB, xHB, or xTB, LDA >= KL+1.
!>          Otherwise, LDA >= max(1,M).
!>
```

*X*

```
!>          X is or output) REAL array, dimension(LDX,NRHS)
!>          On entry, if XTYPE = 'C' (for 'Computed'), then X contains
!>          the exact solution to the system of linear equations.
!>          On exit, if XTYPE = 'N' (for 'New'), then X is initialized
!>          with random values.
!>
```

*LDX*

```
!>          LDX is INTEGER
!>          The leading dimension of the array X.  If TRANS = 'N',
!>          LDX >= max(1,N); if TRANS = 'T', LDX >= max(1,M).
!>
```

*B*

```
!>          B is REAL array, dimension (LDB,NRHS)
!>          The right hand side vector(s) for the system of equations,
!>          computed from B = op(A) * X, where op(A) is determined by
!>          TRANS.
!>
```

*LDB*

```
!>          LDB is INTEGER
!>          The leading dimension of the array B.  If TRANS = 'N',
!>          LDB >= max(1,M); if TRANS = 'T', LDB >= max(1,N).
!>
```

*ISEED*

```
!>          ISEED is INTEGER array, dimension (4)
!>          The seed vector for the random number generator (used in
!>          SLATMS).  Modified on exit.
!>
```

*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

Univ. of Colorado Denver

NAG Ltd.

Definition at line **203** of file **slarhs.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.