# slasq4.f man page

slasq4.f —

## Synopsis

### Functions/Subroutines

subroutineslasq4(I0, N0, Z, PP, N0IN, DMIN, DMIN1, DMIN2, DN, DN1, DN2, TAU, TTYPE, G)SLASQ4computes 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

Univ. of Colorado Denver

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.

## Referenced By

slasq4(3) is an alias of slasq4.f(3).