---
name: "slas2"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/slas2/3lapack"
---

# slas2(3lapack)

computes the singular values of the 2-by-2 matrix \[ F G \] \[ 0 H \]

## NAME

SLAS2 - computes the singular values of the 2-by-2 matrix  \[ F G \]  \[ 0 H \]

## SYNOPSIS

- SUBROUTINE SLAS2(

  F, G, H, SSMIN, SSMAX )

- REAL

  F, G, H, SSMAX, SSMIN

## PURPOSE

SLAS2  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.\

## ARGUMENTS

- F (input) REAL

  The (1,1) element of the 2-by-2 matrix.

- G (input) REAL

  The (1,2) element of the 2-by-2 matrix.

- H (input) REAL

  The (2,2) element of the 2-by-2 matrix.

- SSMIN (output) REAL

  The smaller singular value.

- SSMAX (output) REAL

  The larger singular value.

## 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.\