---
name: "slazq4"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/slazq4"
---

# slazq4(3lapack)

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

## NAME

SLAZQ4 - an approximation TAU to the smallest eigenvalue using values of d from the previous transform

## SYNOPSIS

- SUBROUTINE SLAZQ4(

  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

SLAZQ4 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.\

N0IN  (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 SLAZQ4\

## FURTHER DETAILS

This is a thread safe version of SLASQ4, which passes G through the argument list in place of declaring G in a SAVE statment.