naginterfaces.library.blas.drotgc¶
- naginterfaces.library.blas.drotgc(a, b)[source]¶
drotgc
generates a real Givens plane rotation and the tangent of that rotation.For full information please refer to the NAG Library document for f06ba
https://support.nag.com/numeric/nl/nagdoc_30.2/flhtml/f06/f06baf.html
- Parameters
- afloat
The value , the first element of the vector which determines the rotation.
- bfloat
The value , the second element of the vector which determines the rotation.
- Returns
- afloat
The value .
- bfloat
The value , the tangent of the rotation.
- cfloat
The value , the cosine of the rotation.
- sfloat
The value , the sine of the rotation.
- Notes
No equivalent traditional C interface for this routine exists in the NAG Library.
drotgc
generates a real Givens plane rotation with parameters () and , such that, given real and :On exit, is overwritten by , the tangent of the rotation; and can be reconstructed from the single stored value , by a subsequent call to
dcsg()
.If , where is the machine precision, the function sets and ; if , the function sets and .
Note that is always set to , unless this would overflow, in which case the value is returned, where is the value given by .
To apply the plane rotation to a pair of real vectors, call
drot()
; to apply it to a pair of complex vectors, callzdrot()
.