SGEMV (3) - Linux Manuals


sgemv.f -



subroutine sgemv (TRANS, M, N, ALPHA, A, LDA, X, INCX, BETA, Y, INCY)

Function/Subroutine Documentation

subroutine sgemv (characterTRANS, integerM, integerN, realALPHA, real, dimension(lda,*)A, integerLDA, real, dimension(*)X, integerINCX, realBETA, real, dimension(*)Y, integerINCY)

SGEMV Purpose:

 SGEMV  performs one of the matrix-vector operations

    y := alpha*A*x + beta*y,   or   y := alpha*A**T*x + beta*y,

 where alpha and beta are scalars, x and y are vectors and A is an
 m by n matrix.




          TRANS is CHARACTER*1
           On entry, TRANS specifies the operation to be performed as

              TRANS = 'N' or 'n'   y := alpha*A*x + beta*y.

              TRANS = 'T' or 't'   y := alpha*A**T*x + beta*y.

              TRANS = 'C' or 'c'   y := alpha*A**T*x + beta*y.


          M is INTEGER
           On entry, M specifies the number of rows of the matrix A.
           M must be at least zero.


          N is INTEGER
           On entry, N specifies the number of columns of the matrix A.
           N must be at least zero.


          ALPHA is REAL
           On entry, ALPHA specifies the scalar alpha.


          A is REAL array of DIMENSION ( LDA, n ).
           Before entry, the leading m by n part of the array A must
           contain the matrix of coefficients.


          LDA is INTEGER
           On entry, LDA specifies the first dimension of A as declared
           in the calling (sub) program. LDA must be at least
           max( 1, m ).


          X is REAL array of DIMENSION at least
           ( 1 + ( n - 1 )*abs( INCX ) ) when TRANS = 'N' or 'n'
           and at least
           ( 1 + ( m - 1 )*abs( INCX ) ) otherwise.
           Before entry, the incremented array X must contain the
           vector x.


          INCX is INTEGER
           On entry, INCX specifies the increment for the elements of
           X. INCX must not be zero.


          BETA is REAL
           On entry, BETA specifies the scalar beta. When BETA is
           supplied as zero then Y need not be set on input.


          Y is REAL array of DIMENSION at least
           ( 1 + ( m - 1 )*abs( INCY ) ) when TRANS = 'N' or 'n'
           and at least
           ( 1 + ( n - 1 )*abs( INCY ) ) otherwise.
           Before entry with BETA non-zero, the incremented array Y
           must contain the vector y. On exit, Y is overwritten by the
           updated vector y.


          INCY is INTEGER
           On entry, INCY specifies the increment for the elements of
           Y. INCY must not be zero.



Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.


November 2011

Further Details:

  Level 2 Blas routine.
  The vector and matrix arguments are not referenced when N = 0, or M = 0

  -- Written on 22-October-1986.
     Jack Dongarra, Argonne National Lab.
     Jeremy Du Croz, Nag Central Office.
     Sven Hammarling, Nag Central Office.
     Richard Hanson, Sandia National Labs.


Definition at line 157 of file sgemv.f.


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