?larfx

Developer Reference for Intel® oneAPI Math Kernel Library for C

Download PDF

ID 766684

Date 4/28/2026

Version

Public

?larfx

Applies an elementary reflector to a general rectangular matrix, with loop unrolling when the reflector has order less than or equal to 10.

Syntax

lapack_intLAPACKE_slarfx ( intmatrix_layout , charside , lapack_intm , lapack_intn , constfloat*v , floattau , float*c , lapack_intldc , float*work );

lapack_intLAPACKE_dlarfx ( intmatrix_layout , charside , lapack_intm , lapack_intn , constdouble*v , doubletau , double*c , lapack_intldc , double*work );

lapack_intLAPACKE_clarfx ( intmatrix_layout , charside , lapack_intm , lapack_intn , constlapack_complex_float*v , lapack_complex_floattau , lapack_complex_float*c , lapack_intldc , lapack_complex_float*work );

lapack_intLAPACKE_zlarfx ( intmatrix_layout , charside , lapack_intm , lapack_intn , constlapack_complex_double*v , lapack_complex_doubletau , lapack_complex_double*c , lapack_intldc , lapack_complex_double*work );

Include Files

mkl.h

Description

slarfx dlarfx clarfx zlarfx

The routine ?larfx applies a real/complex elementary reflector H to a real/complex m -by- n matrix C , from either the left or the right.

H is represented in the following forms:

H = I - tau*v*v^{T} , where tau is a real scalar and v is a real vector. H = I - tau*v*v^{H} , where tau is a complex scalar and v is a complex vector.

If tau = 0 , then H is taken to be the unit matrix.

Input Parameters

A <datatype> placeholder, if present, is used for the C interface data types in the C interface section above. See C Interface Conventions for the C interface principal conventions and type definitions.

side

If side = 'L' : form H*C If side = 'R' : form C*H .

m

The number of rows of the matrix C .

n

The number of columns of the matrix C .

v

REAL for slarfx DOUBLE PRECISION for dlarfx COMPLEX for clarfx DOUBLE COMPLEX for zlarfx Array, size ( m ) if side = 'L' or ( n ) if side = 'R' . The vector v in the representation of H .

tau

REAL for slarfx DOUBLE PRECISION for dlarfx COMPLEX for clarfx DOUBLE COMPLEX for zlarfx The value tau in the representation of H .

c

REAL for slarfx DOUBLE PRECISION for dlarfx COMPLEX for clarfx DOUBLE COMPLEX for zlarfx

Array, size at least max(1, ldc * n ) for column major layout and max (1, ldc * m ) for row major layout . On entry, the m -by- n matrix C .

ldc

The leading dimension of the array c . lda ≥ (1, m ).

work: REAL for slarfx DOUBLE PRECISION for dlarfx COMPLEX for clarfx DOUBLE COMPLEX for zlarfx Workspace array, size ( n ) if side = 'L' or ( m ) if side = 'R' . work is not referenced if H has order < 11.

Output Parameters

c: On exit, C is overwritten by the matrix H*C if side = 'L' , or C*H if side = 'R' .

Select Your Language

Using Intel.com Search

Quick Links

Recent Searches

Advanced Search

Only search in

Developer Reference for Intel® oneAPI Math Kernel Library for C

?larfx

Syntax

Include Files

Description

Input Parameters

Output Parameters