Developer Reference for Intel® oneAPI Math Kernel Library for Fortran
p?gemv
Computes a distributed matrix-vector product using a general matrix.
Syntax
call psgemv ( trans , m , n , alpha , a , ia , ja , desca , x , ix , jx , descx , incx , beta , y , iy , jy , descy , incy )
call pdgemv ( trans , m , n , alpha , a , ia , ja , desca , x , ix , jx , descx , incx , beta , y , iy , jy , descy , incy )
call pcgemv ( trans , m , n , alpha , a , ia , ja , desca , x , ix , jx , descx , incx , beta , y , iy , jy , descy , incy )
call pzgemv ( trans , m , n , alpha , a , ia , ja , desca , x , ix , jx , descx , incx , beta , y , iy , jy , descy , incy )
Include Files
mkl_pblas.h
Description
The p?gemv routines perform a distributed matrix-vector operation defined as sub( y ) := alpha *sub( A )*sub( x ) + beta *sub( y ),
or sub( y ) := alpha *sub( A )’*sub( x ) + beta *sub( y ),
or sub( y ) := alpha *conjg(sub( A )’)*sub( x ) + beta *sub( y ),
where
alpha and beta are scalars,
sub(A) is a m-by-n submatrix,sub(A) = A(ia:ia+m-1, ja:ja+n-1) ,
sub(x) and sub(y) are subvectors.
When trans = 'N' or 'n' , sub(x) denotes X(ix, jx:jx+n-1) if incx = m_x , and X(ix: ix+n-1, jx) if incx = 1,sub(y) denotes Y(iy, jy:jy+m-1) if incy = m_y , and Y(iy: iy+m-1, jy) if incy = 1 .
When trans = 'T' or 't' , or 'C' , or 'c' , sub(x) denotes X(ix, jx:jx+m-1) if incx = m_x , and X(ix: ix+m-1, jx) if incx = 1,sub(y) denotes Y(iy, jy:jy+n-1) if incy = m_y , and Y(iy: iy+m-1, jy) if incy = 1 .
Input Parameters
trans
(global) CHARACTER*1 . Specifies the operation:
if trans= 'N' or 'n' , then sub(y) := alpha*sub(A)'*sub(x) + beta*sub(y) ; if trans= 'T' or 't' , then sub(y) := alpha*sub(A)'*sub(x) + beta*sub(y) ; if trans= 'C' or 'c' , then sub(y) := alpha*conjg(subA)')*sub(x) + beta*sub(y) .
m
(global) INTEGER . Specifies the number of rows of the distributed matrix sub(A) , m ≥ 0.
n
(global) INTEGER . Specifies the number of columns of the distributed matrix sub(A) , n ≥ 0.
alpha
(global) REAL for psgemv
DOUBLE PRECISION for pdgemv COMPLEX for pcgemv DOUBLE COMPLEX for pzgemv Specifies the scalar alpha .
a
(local) REAL for psgemv
DOUBLE PRECISION for pdgemv COMPLEX for pcgemv DOUBLE COMPLEX for pzgemv Array, size (lld_a, LOCq(ja+n-1)) . Before entry this array must contain the local pieces of the distributed matrix sub(A) .
ia , ja
(global) INTEGER . The row and column indices in the distributed matrix A indicating the first row and the first column of the submatrix sub(A) , respectively.
desca
(global and local) INTEGER array of dimension 9. The array descriptor of the distributed matrix A .
x
(local) REAL for psgemv
DOUBLE PRECISION for pdgemv COMPLEX for pcgemv DOUBLE COMPLEX for pzgemv Array, size (jx-1)*m_x + ix+(n-1)*abs(incx)) when trans = 'N' or ‘n’ , and (jx-1)*m_x + ix+(m-1)*abs(incx)) otherwise. This array contains the entries of the distributed vector sub(x) .
ix , jx
(global) INTEGER . The row and column indices in the distributed matrix X indicating the first row and the first column of the submatrix sub(x) , respectively.
descx
(global and local) INTEGER array of dimension 9. The array descriptor of the distributed matrix X .
incx
(global) INTEGER . Specifies the increment for the elements of sub(x) . Only two values are supported, namely 1 and m_x . incx must not be zero.
beta
(global) REAL for psgemv
DOUBLE PRECISION for pdgemv COMPLEX for pcgemv DOUBLE COMPLEX for pzgemv Specifies the scalar beta . When beta is set to zero, then sub(y) need not be set on input.
y
(local) REAL for psgemv
DOUBLE PRECISION for pdgemv COMPLEX for pcgemv DOUBLE COMPLEX for pzgemv Array, size (jy-1)*m_y + iy+(m-1)*abs(incy)) when trans = 'N' or ‘n’ , and (jy-1)*m_y + iy+(n-1)*abs(incy)) otherwise. This array contains the entries of the distributed vector sub(y) .
iy , jy
(global) INTEGER . The row and column indices in the distributed matrix Y indicating the first row and the first column of the submatrix sub(y) , respectively.
descy
(global and local) INTEGER array of dimension 9. The array descriptor of the distributed matrix Y .
incy
(global) INTEGER . Specifies the increment for the elements of sub(y) . Only two values are supported, namely 1 and m_y . incy must not be zero.
Output Parameters
- y
-
Overwritten by the updated distributed vector sub(y) .