?lartg

Generates a plane rotation with real cosine and real/complex sine.

Syntax

call slartg( f, g, cs, sn, r )

call dlartg( f, g, cs, sn, r )

call clartg( f, g, cs, sn, r )

call zlartg( f, g, cs, sn, r )

The routine generates a plane rotation so that

where cs² + |sn|² = 1

This is a slower, more accurate version of the BLAS Level 1 routine ?rotg, except for the following differences.

For slartg/dlartg:

f and g are unchanged on return;

If g=0, then cs=1 and sn=0;

If f=0 and g≠ 0, then cs=0 and sn=1 without doing any floating point operations (saves work in ?bdsqr when there are zeros on the diagonal);

If f exceeds g in magnitude, cs will be positive.

For clartg/zlartg:

f and g are unchanged on return;

If g=0, then cs=1 and sn=0;

If f=0, then cs=0 and sn is chosen so that r is real.

f, g

REAL for slartg

DOUBLE PRECISION for dlartg

COMPLEX for clartg

DOUBLE COMPLEX for zlartg

The first and second component of vector to be rotated.

cs

REAL for slartg/clartg

DOUBLE PRECISION for dlartg/zlartg

The cosine of the rotation.

sn

REAL for slartg

DOUBLE PRECISION for dlartg

COMPLEX for clartg

DOUBLE COMPLEX for zlartg

The sine of the rotation.

r

REAL for slartg

DOUBLE PRECISION for dlartg

COMPLEX for clartg

DOUBLE COMPLEX for zlartg

The nonzero component of the rotated vector.