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<TITLE>HPL_dgemv HPL 2.0 Library Functions September 10, 2008</TITLE> |
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ALINK = "#ffff00"> |
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<H1>Name</H1> |
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<B>HPL_dgemv</B> y := beta * y + alpha * op(A) * x. |
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<H1>Synopsis</H1> |
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<CODE>#include "hpl.h"</CODE><BR><BR> |
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<CODE>void</CODE> |
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<CODE>HPL_dgemv(</CODE> |
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<CODE>const enum HPL_ORDER</CODE> |
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<CODE>ORDER</CODE>, |
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<CODE>const enum HPL_TRANS</CODE> |
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<CODE>TRANS</CODE>, |
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<CODE>const int</CODE> |
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<CODE>M</CODE>, |
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<CODE>const int</CODE> |
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<CODE>N</CODE>, |
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<CODE>const double</CODE> |
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<CODE>ALPHA</CODE>, |
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<CODE>const double *</CODE> |
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<CODE>A</CODE>, |
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<CODE>const int</CODE> |
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<CODE>LDA</CODE>, |
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<CODE>const double *</CODE> |
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<CODE>X</CODE>, |
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<CODE>const int</CODE> |
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<CODE>INCX</CODE>, |
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<CODE>const double</CODE> |
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<CODE>BETA</CODE>, |
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<CODE>double *</CODE> |
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<CODE>Y</CODE>, |
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<CODE>const int</CODE> |
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<CODE>INCY</CODE> |
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<CODE>);</CODE> |
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<H1>Description</H1> |
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<B>HPL_dgemv</B> |
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performs one of the matrix-vector operations |
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y := alpha * op( A ) * x + beta * y, |
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where op( X ) is one of |
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op( X ) = X or op( X ) = X^T. |
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where alpha and beta are scalars, x and y are vectors and A is an m |
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by n matrix. |
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<H1>Arguments</H1> |
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<PRE>
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ORDER (local input) const enum HPL_ORDER |
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On entry, ORDER specifies the storage format of the operands |
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as follows: |
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ORDER = HplRowMajor, |
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ORDER = HplColumnMajor. |
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</PRE>
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<PRE>
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TRANS (local input) const enum HPL_TRANS |
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On entry, TRANS specifies the operation to be performed as |
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follows: |
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TRANS = HplNoTrans y := alpha*A *x + beta*y, |
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TRANS = HplTrans y := alpha*A^T*x + beta*y. |
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</PRE>
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<PRE>
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M (local input) const int |
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On entry, M specifies the number of rows of the matrix A. |
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M must be at least zero. |
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</PRE>
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<PRE>
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N (local input) const int |
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On entry, N specifies the number of columns of the matrix A. |
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N must be at least zero. |
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</PRE>
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<PRE>
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ALPHA (local input) const double |
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On entry, ALPHA specifies the scalar alpha. When ALPHA is |
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supplied as zero then A and X need not be set on input. |
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</PRE>
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<PRE>
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A (local input) const double * |
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On entry, A points to an array of size equal to or greater |
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than LDA * n. Before entry, the leading m by n part of the |
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array A must contain the matrix coefficients. |
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</PRE>
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<PRE>
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LDA (local input) const int |
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On entry, LDA specifies the leading dimension of A as |
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declared in the calling (sub) program. LDA must be at |
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least MAX(1,m). |
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</PRE>
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<PRE>
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X (local input) const double * |
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On entry, X is an incremented array of dimension at least |
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( 1 + ( n - 1 ) * abs( INCX ) ) that contains the vector x. |
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</PRE>
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<PRE>
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INCX (local input) const int |
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On entry, INCX specifies the increment for the elements of X. |
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INCX must not be zero. |
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</PRE>
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<PRE>
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BETA (local input) const double |
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On entry, BETA specifies the scalar beta. When ALPHA is |
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supplied as zero then Y need not be set on input. |
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</PRE>
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<PRE>
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Y (local input/output) double * |
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On entry, Y is an incremented array of dimension at least |
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( 1 + ( n - 1 ) * abs( INCY ) ) that contains the vector y. |
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Before entry with BETA non-zero, the incremented array Y must |
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contain the vector y. On exit, Y is overwritten by the |
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updated vector y. |
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</PRE>
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<PRE>
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INCY (local input) const int |
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On entry, INCY specifies the increment for the elements of Y. |
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INCY must not be zero. |
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</PRE>
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<H1>Example</H1> |
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<CODE>#include "hpl.h"</CODE><BR><BR> |
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<PRE>
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int main(int argc, char *argv[]) |
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{
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double a[2*2], x[2], y[2]; |
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a[0] = 1.0; a[1] = 2.0; a[2] = 3.0; a[3] = 3.0; |
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x[0] = 2.0; x[1] = 1.0; y[2] = 1.0; y[3] = 2.0; |
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HPL_dgemv( HplColumnMajor, HplNoTrans, 2, 2, 2.0, |
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a, 2, x, 1, -1.0, y, 1 ); |
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printf("y=[%f,%f]\n", y[0], y[1]);
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exit(0); return(0); |
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} |
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</PRE>
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<H1>See Also</H1> |
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<A HREF="HPL_dger.html">HPL_dger</A>, |
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<A HREF="HPL_dtrsv.html">HPL_dtrsv</A>. |
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