dlasq6.f

Section: LAPACK (3)
Updated: Tue Nov 14 2017
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dlasq6.f

SYNOPSIS

Functions/Subroutines

subroutine dlasq6 (I0, N0, Z, PP, DMIN, DMIN1, DMIN2, DN, DNM1, DNM2)
DLASQ6 computes one dqd transform in ping-pong form. Used by sbdsqr and sstegr.

Function/Subroutine Documentation

subroutine dlasq6 (integer I0, integer N0, double precision, dimension( * ) Z, integer PP, double precision DMIN, double precision DMIN1, double precision DMIN2, double precision DN, double precision DNM1, double precision DNM2)

DLASQ6 computes one dqd transform in ping-pong form. Used by sbdsqr and sstegr.

Purpose:

``` DLASQ6 computes one dqd (shift equal to zero) transform in
ping-pong form, with protection against underflow and overflow.
```

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. EMIN is stored in Z(4*N0) to avoid
an extra argument.
```

PP

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

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(N0), the last value of d.
```

DNM1

```          DNM1 is DOUBLE PRECISION
d(N0-1).
```

DNM2

```          DNM2 is DOUBLE PRECISION
d(N0-2).
```

Author:

Univ. of Tennessee

Univ. of California Berkeley