Developer Reference for Intel® oneAPI Math Kernel Library for Fortran
?larfy
Applies an elementary reflector, or Householder matrix, H, to an n by n symmetric or Hermitian matrix C, from both the left and the right.
Syntax
call slarfy ( uplo , n , v , incv , tau , C , ldc , work )
call dlarfy ( uplo , n , v , incv , tau , C , ldc , work )
call clarfy ( uplo , n , v , incv , tau , C , ldc , work )
call zlarfy ( uplo , n , v , incv , tau , C , ldc , work )
Description
?larfy applies an elementary reflector, or Householder matrix, H, to an n by n symmetric or Hermitian matrix C, from both the left and the right. H is represented in the form H = I - tau * v * vT (for real flavors) or H = I - tau * v * vH (for complex flavors), where tau is a scalar and v is a vector. If tau is zero, H is taken to be the unit matrix.
Input Parameters
- uplo
-
CHARACTER*1 Specifies whether the upper or lower triangular part of the symmetric or Hermitian matrix C is stored.
- n
-
INTEGER The number of rows and columns of the matrix C. n ≥ 0.
- v
-
REAL for slarfy DOUBLE PRECISION for dlarfy COMPLEX for clarfy COMPLEX*16 for zlarfy Array, dimension (1 + ( n- 1)*abs( incv )). The vector v as described above.
- incv
-
INTEGER The increment between successive elements of v. incv must not be zero.
- tau
-
REAL for slarfy DOUBLE PRECISION for dlarfy COMPLEX for clarfy COMPLEX*16 for zlarfy The value tau as described above.
- C
-
REAL for slarfy DOUBLE PRECISION for dlarfy COMPLEX for clarfy COMPLEX*16 for zlarfy Array, dimension ( ldc , n ). On entry, the matrix C.
- ldc
-
INTEGER The leading dimension of the array C . ldc ≥ max( 1, n ).
Output Parameters
- C
-
REAL for slarfy DOUBLE PRECISION for dlarfy COMPLEX for clarfy COMPLEX*16 for zlarfy On exit, C is overwritten by H * C * H T (for real flavors) or H * C * H H (for complex flavors).
- work
-
REAL for slarfy DOUBLE PRECISION for dlarfy COMPLEX for clarfy COMPLEX*16 for zlarfy Array, dimension ( n ).