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 )
Include Files
The FORTRAN 77 interfaces are specified in the mkl_lapack.fi include file (to be used in Fortran programs) and in the mkl_lapack.h include file (to be used in C programs).
Description
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.
Input Parameters
- f, g
REAL for slartg
DOUBLE PRECISION for dlartg
COMPLEX for clartg
COMPLEX*16 for zlartg
The first and second component of vector to be rotated.
Output Parameters
- 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
COMPLEX*16 for zlartg
The sine of the rotation.
- r
REAL for slartg
DOUBLE PRECISION for dlartg
COMPLEX for clartg
COMPLEX*16 for zlartg
The nonzero component of the rotated vector.