# slasq4.f(3) [centos man page]

```slasq4.f(3)							      LAPACK							       slasq4.f(3)

NAME
slasq4.f -

SYNOPSIS
Functions/Subroutines
subroutine slasq4 (I0, N0, Z, PP, N0IN, DMIN, DMIN1, DMIN2, DN, DN1, DN2, TAU, TTYPE, G)
SLASQ4 computes an approximation to the smallest eigenvalue using values of d from the previous transform. Used by sbdsqr.

Function/Subroutine Documentation
subroutine slasq4 (integerI0, integerN0, real, dimension( * )Z, integerPP, integerN0IN, realDMIN, realDMIN1, realDMIN2, realDN, realDN1,
realDN2, realTAU, integerTTYPE, realG)
SLASQ4 computes an approximation to the smallest eigenvalue using values of d from the previous transform. Used by sbdsqr.

Purpose:

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

Parameters:
I0

I0 is INTEGER
First index.

N0

N0 is INTEGER
Last index.

Z

Z is REAL array, dimension ( 4*N )
Z holds the qd array.

PP

PP is INTEGER
PP=0 for ping, PP=1 for pong.

N0IN

N0IN is INTEGER
The value of N0 at start of EIGTEST.

DMIN

DMIN is REAL
Minimum value of d.

DMIN1

DMIN1 is REAL
Minimum value of d, excluding D( N0 ).

DMIN2

DMIN2 is REAL
Minimum value of d, excluding D( N0 ) and D( N0-1 ).

DN

DN is REAL
d(N)

DN1

DN1 is REAL
d(N-1)

DN2

DN2 is REAL
d(N-2)

TAU

TAU is REAL
This is the shift.

TTYPE

TTYPE is INTEGER
Shift type.

G

G is REAL
G is passed as an argument in order to save its value between
calls to SLASQ4.

Author:
Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Date:
September 2012

Further Details:

CNST1 = 9/16

Definition at line 151 of file slasq4.f.

Author
Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2							  Tue Sep 25 2012						       slasq4.f(3)```

## Check Out this Related Man Page

```slasq3.f(3)							      LAPACK							       slasq3.f(3)

NAME
slasq3.f -

SYNOPSIS
Functions/Subroutines
subroutine slasq3 (I0, N0, Z, PP, DMIN, SIGMA, DESIG, QMAX, NFAIL, ITER, NDIV, IEEE, TTYPE, DMIN1, DMIN2, DN, DN1, DN2, G, TAU)
SLASQ3 checks for deflation, computes a shift and calls dqds. Used by sbdsqr.

Function/Subroutine Documentation
subroutine slasq3 (integerI0, integerN0, real, dimension( * )Z, integerPP, realDMIN, realSIGMA, realDESIG, realQMAX, integerNFAIL, integerITER,
integerNDIV, logicalIEEE, integerTTYPE, realDMIN1, realDMIN2, realDN, realDN1, realDN2, realG, realTAU)
SLASQ3 checks for deflation, computes a shift and calls dqds. Used by sbdsqr.

Purpose:

SLASQ3 checks for deflation, computes a shift (TAU) and calls dqds.
In case of failure it changes shifts, and tries again until output
is positive.

Parameters:
I0

I0 is INTEGER
First index.

N0

N0 is INTEGER
Last index.

Z

Z is REAL array, dimension ( 4*N )
Z holds the qd array.

PP

PP is INTEGER
PP=0 for ping, PP=1 for pong.
PP=2 indicates that flipping was applied to the Z array
and that the initial tests for deflation should not be
performed.

DMIN

DMIN is REAL
Minimum value of d.

SIGMA

SIGMA is REAL
Sum of shifts used in current segment.

DESIG

DESIG is REAL
Lower order part of SIGMA

QMAX

QMAX is REAL
Maximum value of q.

NFAIL

NFAIL is INTEGER
Number of times shift was too big.

ITER

ITER is INTEGER
Number of iterations.

NDIV

NDIV is INTEGER
Number of divisions.

IEEE

IEEE is LOGICAL
Flag for IEEE or non IEEE arithmetic (passed to SLASQ5).

TTYPE

TTYPE is INTEGER
Shift type.

DMIN1

DMIN1 is REAL

DMIN2

DMIN2 is REAL

DN

DN is REAL

DN1

DN1 is REAL

DN2

DN2 is REAL

G

G is REAL

TAU

TAU is REAL

These are passed as arguments in order to save their values
between calls to SLASQ3.

Author:
Univ. of Tennessee

Univ. of California Berkeley