---
name: "dlas2"
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/dlas2.f"
---

# dlas2(3)

Part of [dlas2.f(3)](/dlas2.f/3.md).

## NAME

SRC/dlas2.f

## SYNOPSIS

### Functions/Subroutines

subroutine **dlas2** (f, g, h, ssmin, ssmax)\
 **DLAS2** computes singular values of a 2-by-2 triangular matrix.

## Function/Subroutine Documentation

### subroutine dlas2 (double precision f, double precision g, double precision h, double precision ssmin, double precision ssmax)

**DLAS2** computes singular values of a 2-by-2 triangular matrix.

**Purpose:**

```
!>
!> DLAS2  computes the singular values of the 2-by-2 matrix
!>    [  F   G  ]
!>    [  0   H  ].
!> On return, SSMIN is the smaller singular value and SSMAX is the
!> larger singular value.
!>
```

**Parameters**

*F*

```
!>          F is DOUBLE PRECISION
!>          The (1,1) element of the 2-by-2 matrix.
!>
```

*G*

```
!>          G is DOUBLE PRECISION
!>          The (1,2) element of the 2-by-2 matrix.
!>
```

*H*

```
!>          H is DOUBLE PRECISION
!>          The (2,2) element of the 2-by-2 matrix.
!>
```

*SSMIN*

```
!>          SSMIN is DOUBLE PRECISION
!>          The smaller singular value.
!>
```

*SSMAX*

```
!>          SSMAX is DOUBLE PRECISION
!>          The larger singular value.
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Further Details:**

```
!>
!>  Barring over/underflow, all output quantities are correct to within
!>  a few units in the last place (ulps), even in the absence of a guard
!>  digit in addition/subtraction.
!>
!>  In IEEE arithmetic, the code works correctly if one matrix element is
!>  infinite.
!>
!>  Overflow will not occur unless the largest singular value itself
!>  overflows, or is within a few ulps of overflow.
!>
!>  Underflow is harmless if underflow is gradual. Otherwise, results
!>  may correspond to a matrix modified by perturbations of size near
!>  the underflow threshold.
!>
```

Definition at line **104** of file **dlas2.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.