# DLASQ4 (3) - Linux Manuals

dlasq4.f -

## SYNOPSIS

### Functions/Subroutines

subroutine dlasq4 (I0, N0, Z, PP, N0IN, DMIN, DMIN1, DMIN2, DN, DN1, DN2, TAU, TTYPE, G)
DLASQ4 computes an approximation to the smallest eigenvalue using values of d from the previous transform. Used by sbdsqr.

## Function/Subroutine Documentation

### subroutine dlasq4 (integerI0, integerN0, double precision, dimension( * )Z, integerPP, integerN0IN, double precisionDMIN, double precisionDMIN1, double precisionDMIN2, double precisionDN, double precisionDN1, double precisionDN2, double precisionTAU, integerTTYPE, double precisionG)

DLASQ4 computes an approximation to the smallest eigenvalue using values of d from the previous transform. Used by sbdsqr.

Purpose:

``` DLASQ4 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 DOUBLE PRECISION 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 DOUBLE PRECISION
Minimum value of d.
```

DMIN1

```          DMIN1 is DOUBLE PRECISION
Minimum value of d, excluding D( N0 ).
```

DMIN2

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

DN

```          DN is DOUBLE PRECISION
d(N)
```

DN1

```          DN1 is DOUBLE PRECISION
d(N-1)
```

DN2

```          DN2 is DOUBLE PRECISION
d(N-2)
```

TAU

```          TAU is DOUBLE PRECISION
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 DLASQ4.
```

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Further Details:

```  CNST1 = 9/16
```

Definition at line 151 of file dlasq4.f.

## Author

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