---
name: "slasq4"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/slasq4/3lapack"
---

# slasq4(3lapack)

computes an approximation TAU to the smallest eigenvalue using values of d from the previous transform

## NAME

SLASQ4 - computes an approximation TAU to the smallest eigenvalue using values of d from the previous transform

## SYNOPSIS

- SUBROUTINE SLASQ4(

  I0, N0, Z, PP, N0IN, DMIN, DMIN1, DMIN2, DN, DN1, DN2, TAU, TTYPE, G )

- INTEGER

  I0, N0, N0IN, PP, TTYPE

- REAL

  DMIN, DMIN1, DMIN2, DN, DN1, DN2, G, TAU

- REAL

  Z( \* )

## PURPOSE

SLASQ4 computes an approximation TAU to the smallest eigenvalue using values of d from the previous transform. I0    (input) INTEGER\
\
       First index.\
 N0    (input) INTEGER\
\
       Last index.\
 Z     (input) REAL array, dimension ( 4\*N )\
\
       Z holds the qd array.\
 PP    (input) INTEGER\
\
       PP=0 for ping, PP=1 for pong.\
 NOIN  (input) INTEGER\
\
       The value of N0 at start of EIGTEST.\
 DMIN  (input) REAL\
\
       Minimum value of d.\
 DMIN1 (input) REAL\
\
       Minimum value of d, excluding D( N0 ).\
 DMIN2 (input) REAL\
\
       Minimum value of d, excluding D( N0 ) and D( N0-1 ). DN    (input) REAL\
\
       d(N)\
 DN1   (input) REAL\
\
       d(N-1)\
 DN2   (input) REAL\
\
       d(N-2)\
 TAU   (output) REAL\
\
       This is the shift.\
 TTYPE (output) INTEGER\
\
       Shift type.\
 G     (input/output) REAL\
\
       G is passed as an argument in order to save its value between\
       calls to SLASQ4.\

## FURTHER DETAILS