---
name: "slasy2"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/slasy2/3lapack"
---

# slasy2(3lapack)

solves for the N1 by N2 matrix X, 1 \<= N1,N2 \<= 2, in op(TL)\*X + ISGN\*X\*op(TR) = SCALE\*B,

## NAME

SLASY2 - solves for the N1 by N2 matrix X, 1 \<= N1,N2 \<= 2, in   op(TL)\*X + ISGN\*X\*op(TR) = SCALE\*B,

## SYNOPSIS

- SUBROUTINE SLASY2(

  LTRANL, LTRANR, ISGN, N1, N2, TL, LDTL, TR, LDTR, B, LDB, SCALE, X, LDX, XNORM, INFO )

- LOGICAL

  LTRANL, LTRANR

- INTEGER

  INFO, ISGN, LDB, LDTL, LDTR, LDX, N1, N2

- REAL

  SCALE, XNORM

- REAL

  B( LDB, \* ), TL( LDTL, \* ), TR( LDTR, \* ), X( LDX, \* )

## PURPOSE

SLASY2 solves for the N1 by N2 matrix X, 1 \<= N1,N2 \<= 2, in where TL is N1 by N1, TR is N2 by N2, B is N1 by N2, and ISGN = 1 or -1.  op(T) = T or T', where T' denotes the transpose of T.

## ARGUMENTS

- LTRANL (input) LOGICAL

  On entry, LTRANL specifies the op(TL): = .FALSE., op(TL) = TL, = .TRUE., op(TL) = TL'.

- LTRANR (input) LOGICAL

  On entry, LTRANR specifies the op(TR): = .FALSE., op(TR) = TR, = .TRUE., op(TR) = TR'.

- ISGN (input) INTEGER

  On entry, ISGN specifies the sign of the equation as described before. ISGN may only be 1 or -1.

- N1 (input) INTEGER

  On entry, N1 specifies the order of matrix TL. N1 may only be 0, 1 or 2.

- N2 (input) INTEGER

  On entry, N2 specifies the order of matrix TR. N2 may only be 0, 1 or 2.

- TL (input) REAL array, dimension (LDTL,2)

  On entry, TL contains an N1 by N1 matrix.

- LDTL (input) INTEGER

  The leading dimension of the matrix TL. LDTL \>= max(1,N1).

- TR (input) REAL array, dimension (LDTR,2)

  On entry, TR contains an N2 by N2 matrix.

- LDTR (input) INTEGER

  The leading dimension of the matrix TR. LDTR \>= max(1,N2).

- B (input) REAL array, dimension (LDB,2)

  On entry, the N1 by N2 matrix B contains the right-hand side of the equation.

- LDB (input) INTEGER

  The leading dimension of the matrix B. LDB \>= max(1,N1).

- SCALE (output) REAL

  On exit, SCALE contains the scale factor. SCALE is chosen less than or equal to 1 to prevent the solution overflowing.

- X (output) REAL array, dimension (LDX,2)

  On exit, X contains the N1 by N2 solution.

- LDX (input) INTEGER

  The leading dimension of the matrix X. LDX \>= max(1,N1).

- XNORM (output) REAL

  On exit, XNORM is the infinity-norm of the solution.

- INFO (output) INTEGER

  On exit, INFO is set to 0: successful exit.\
   1: TL and TR have too close eigenvalues, so TL or TR is perturbed to get a nonsingular equation. NOTE: In the interests of speed, this routine does not check the inputs for errors.