# slartgs.f man page

slartgs.f —

## Synopsis

### Functions/Subroutines

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

## Function/Subroutine Documentation

### subroutine slartgs (realX, realY, realSIGMA, realCS, realSN)

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

**Purpose:**

```
SLARTGS 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 REAL
The (1,1) entry of an upper bidiagonal matrix.
```

*Y*

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

*SIGMA*

```
SIGMA is REAL
The shift.
```

*CS*

```
CS is REAL
The cosine of the rotation.
```

*SN*

```
SN is REAL
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 slartgs.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

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