dlartgs.f (3) - Linux Man Pages

dlartgs.f -

SYNOPSIS

Functions/Subroutines

subroutine dlartgs (X, Y, SIGMA, CS, SN)
DLARTGS generates a plane rotation designed to introduce a bulge in implicit QR iteration for the bidiagonal SVD problem.

Function/Subroutine Documentation

subroutine dlartgs (double precisionX, double precisionY, double precisionSIGMA, double precisionCS, double precisionSN)

DLARTGS generates a plane rotation designed to introduce a bulge in implicit QR iteration for the bidiagonal SVD problem.

Purpose:

``` DLARTGS generates a plane rotation designed to introduce a bulge in
Golub-Reinsch-style implicit QR iteration for the bidiagonal SVD
problem. X and Y are the top-row entries, and SIGMA is the shift.
The computed CS and SN define a plane rotation satisfying

[  CS  SN  ]  .  [ X^2 - SIGMA ]  =  [ R ],
[ -SN  CS  ]     [    X * Y    ]     [ 0 ]

with R nonnegative.  If X^2 - SIGMA and X * Y are 0, then the
rotation is by PI/2.
```

Parameters:

X

```          X is DOUBLE PRECISION
The (1,1) entry of an upper bidiagonal matrix.
```

Y

```          Y is DOUBLE PRECISION
The (1,2) entry of an upper bidiagonal matrix.
```

SIGMA

```          SIGMA is DOUBLE PRECISION
The shift.
```

CS

```          CS is DOUBLE PRECISION
The cosine of the rotation.
```

SN

```          SN is DOUBLE PRECISION
The sine of the rotation.
```

Author:

Univ. of Tennessee

Univ. of California Berkeley