Developer Reference for Intel® oneAPI Math Kernel Library for Fortran
?larfp
Generates a real or complex elementary reflector.
Syntax
call slarfp ( n , alpha , x , incx , tau )
call dlarfp ( n , alpha , x , incx , tau )
call clarfp ( n , alpha , x , incx , tau )
call zlarfp ( n , alpha , x , incx , tau )
Include Files
mkl.fi
Description
slarfp dlarfp clarfp zlarfp larfp
The ?larfp routines generate a real or complex elementary reflector H of order n , such that
H * ( alpha ) = ( beta ), ( x ) ( 0 )
and H'*H =I for real flavors, conjg(H)'*H =I for complex flavors.
Here
alpha and beta are scalars, beta is real and non-negative,
x is (n-1) -element vector.
H is represented in the form
H = I - tau *( 1 )* (1 v ‘), ( v )
where tau is scalar, and v is (n-1) -element vector .
For real flavors if the elements of x are all zero, then tau = 0 and H is taken to be the unit matrix. Otherwise 1 ≤tau≤ 2 .
For complex flavors if the elements of x are all zero and alpha is real, then tau = 0 and H is taken to be the unit matrix. Otherwise 1 ≤ real(tau) ≤ 2 , and abs (tau-1≤ 1 .
Input Parameters
- n
-
INTEGER . Specifies the order of the elementary reflector.
- alpha
-
REAL for slarfp DOUBLE PRECISION for dlarfp COMPLEX for clarfp DOUBLE COMPLEX for zlarfp Specifies the scalar alpha .
- x
-
REAL for slarfp DOUBLE PRECISION for dlarfp COMPLEX for clarfp DOUBLE COMPLEX for zlarfp Array, DIMENSION at least (1 + (n - 1)*abs(incx)) . It contains the vector x .
- incx
-
INTEGER . Specifies the increment for the elements of x . The value of incx must not be zero.
Output Parameters
- alpha
-
Overwritten by the value beta .
- y
-
Overwritten by the vector v .
- tau
-
REAL for slarfp DOUBLE PRECISION for dlarfp COMPLEX for clarfp DOUBLE COMPLEX for zlarfp Contains the scalar tau .