# dlartgs.f man page

dlartgs.f —

## Synopsis

### Functions/Subroutines

subroutinedlartgs(X, Y, SIGMA, CS, SN)DLARTGSgenerates 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

Univ. of Colorado Denver

NAG Ltd.

**Date:**

September 2012

Definition at line 91 of file dlartgs.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

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

Sat Nov 16 2013 Version 3.4.2 LAPACK