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Technical Reference: Base Operating System and Extensions , Volume 2
Performs matrixvector operation
with general matrices.
BLAS Library
(libblas.a)
SUBROUTINE SGEMV(TRANS, M, N, ALPHA, A, LDA, X,
INCX, BETA, Y, INCY)
REAL ALPHA, BETA
INTEGER INCX, INCY, LDA, M, N
CHARACTER*1 TRANS
REAL A(LDA,*), X(*), Y(*)
SUBROUTINE DGEMV(TRANS, M, N, ALPHA, A, LDA, X,
INCX, BETA, Y, INCY)
DOUBLE PRECISION ALPHA,BETA
INTEGER INCX,INCY,LDA,M,N
CHARACTER*1 TRANS
DOUBLE PRECISION A(LDA,*), X(*), Y(*)
SUBROUTINE CGEMV(TRANS, M, N, ALPHA, A, LDA, X,
INCX, BETA, Y, INCY)
COMPLEX ALPHA,BETA
INTEGER INCX,INCY,LDA,M,N
CHARACTER*1 TRANS
COMPLEX A(LDA,*), X(*), Y(*)
SUBROUTINE ZGEMV(TRANS, M, N, ALPHA, A, LDA, X,
INCX, BETA, Y, INCY)
COMPLEX*16 ALPHA,BETA
INTEGER INCX,INCY,LDA,M,N
CHARACTER*1 TRANS
COMPLEX*16 A(LDA,*), X(*), Y(*)
The SGEMV,
DGEMV, CGEMV, or ZGEMV subroutine performs
one of the following matrixvector operations:
y := alpha
* A * x + beta * y
OR
y := alpha
* A' * x + beta * y
where alpha and beta are scalars,
x and y are vectors, and A is an M by N
matrix.
TRANS
 On entry, TRANS specifies the operation to be performed as
follows:
 TRANS = 'N' or
'n'
 y := alpha * A * x + beta * y
 TRANS = 'T'
or 't'
 y := alpha * A' * x + beta * y
 TRANS = 'C'
or 'c'
 y := alpha * A' * x + beta * y
Unchanged on exit.

M
 On entry, M specifies the number of rows of the matrix
A; M must be at least 0; unchanged on
exit.

N
 On entry, N specifies the number of columns of the matrix
A; N must be at least 0; unchanged on
exit.

ALPHA
 On entry, ALPHA specifies the scalar alpha; unchanged on
exit.

A
 An array of dimension ( LDA, N ); on entry,
the leading M by N part of the array A must
contain the matrix of coefficients; unchanged on exit.

LDA
 On entry, LDA specifies the first dimension of A as
declared in the calling (sub) program; LDA must be at least
max( 1, M ); unchanged on exit.

X
 A vector of dimension at least (1 + (N1) * abs(
INCX ) ) when TRANS = 'N' or 'n',
otherwise, at least (1 + (M1) * abs( INCX ) ); on
entry, the incremented array X must contain the vector x;
unchanged on exit.

INCX
 On entry, INCX specifies the increment for the elements of
X; INCX must not be 0; unchanged on
exit.

BETA
 On entry, BETA specifies the scalar beta; when
BETA is supplied as 0, Y need not be set on input;
unchanged on exit.

Y
 A vector of dimension at least 1 + (M1) * abs(
INCY ) ) when TRANS = 'N' or 'n',
otherwise at least (1 + (N1) * abs( INCY ) ); on
entry, with BETA nonzero, the incremented array Y must
contain the vector y; on exit, Y is overwritten by the updated
vector y.

INCY
 On entry, INCY specifies the increment for the elements of
Y; INCY must not be 0; unchanged on
exit.

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