---
name: "xlaenv.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/xlaenv.f"
---

# xlaenv.f(3)

## NAME

TESTING/LIN/xlaenv.f

## SYNOPSIS

### Functions/Subroutines

subroutine **xlaenv** (ispec, nvalue)\
 **XLAENV**

## Function/Subroutine Documentation

### subroutine xlaenv (integer ispec, integer nvalue)

**XLAENV**

**Purpose:**

```
!>
!> XLAENV sets certain machine- and problem-dependent quantities
!> which will later be retrieved by ILAENV.
!>
```

**Parameters**

*ISPEC*

```
!>          ISPEC is INTEGER
!>          Specifies the parameter to be set in the COMMON array IPARMS.
!>          = 1: the optimal blocksize; if this value is 1, an unblocked
!>               algorithm will give the best performance.
!>          = 2: the minimum block size for which the block routine
!>               should be used; if the usable block size is less than
!>               this value, an unblocked routine should be used.
!>          = 3: the crossover point (in a block routine, for N less
!>               than this value, an unblocked routine should be used)
!>          = 4: the number of shifts, used in the nonsymmetric
!>               eigenvalue routines
!>          = 5: the minimum column dimension for blocking to be used;
!>               rectangular blocks must have dimension at least k by m,
!>               where k is given by ILAENV(2,...) and m by ILAENV(5,...)
!>          = 6: the crossover point for the SVD (when reducing an m by n
!>               matrix to bidiagonal form, if max(m,n)/min(m,n) exceeds
!>               this value, a QR factorization is used first to reduce
!>               the matrix to a triangular form)
!>          = 7: the number of processors
!>          = 8: another crossover point, for the multishift QR and QZ
!>               methods for nonsymmetric eigenvalue problems.
!>          = 9: maximum size of the subproblems at the bottom of the
!>               computation tree in the divide-and-conquer algorithm
!>               (used by xGELSD and xGESDD)
!>          =10: ieee NaN arithmetic can be trusted not to trap
!>          =11: infinity arithmetic can be trusted not to trap
!>
```

*NVALUE*

```
!>          NVALUE is INTEGER
!>          The value of the parameter specified by ISPEC.
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **77** of file **xlaenv.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.