# dlas2.f man page

dlas2.f —

## Synopsis

### Functions/Subroutines

subroutinedlas2(F, G, H, SSMIN, SSMAX)DLAS2computes singular values of a 2-by-2 triangular matrix.

## Function/Subroutine Documentation

### subroutine dlas2 (double precisionF, double precisionG, double precisionH, double precisionSSMIN, double precisionSSMAX)

**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.

**Date:**

September 2012

**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. (On machines with
partial overflow, like the Cray, overflow may occur if the largest
singular value is within a factor of 2 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 108 of file dlas2.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

dlas2(3) is an alias of dlas2.f(3).