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/*================================================================
* spmtimesd.c
* This routine computes a sparse matrix times a diagonal matrix
* whose diagonal entries are stored in a full vector.
*
* Examples:
* spmtimesd(m,d,[]) = diag(d) * m,
* spmtimesd(m,[],d) = m * diag(d)
* spmtimesd(m,d1,d2) = diag(d1) * m * diag(d2)
* m could be complex, but d is assumed real
*
* Stella X. Yu's first MEX function, Nov 9, 2001.
% test sequence:
m = 1000;
n = 2000;
a=sparse(rand(m,n));
d1 = rand(m,1);
d2 = rand(n,1);
tic; b=spmtimesd(a,d1,d2); toc
tic; bb = spdiags(d1,0,m,m) * a * spdiags(d2,0,n,n); toc
e = (bb-b);
max(abs(e(:)))
*=================================================================*/
# include "mex.h"
void mexFunction(
int nargout,
mxArray *out[],
int nargin,
const mxArray *in[]
)
{
/* declare variables */
int i, j, k, m, n, nzmax, cmplx, xm, yn;
int *pir, *pjc, *qir, *qjc;
double *x, *y, *pr, *pi, *qr, *qi;
/* check argument */
if (nargin != 3) {
mexErrMsgTxt("Three input arguments required");
}
if (nargout>1) {
mexErrMsgTxt("Too many output arguments.");
}
if (!(mxIsSparse(in[0]))) {
mexErrMsgTxt("Input argument #1 must be of type sparse");
}
if ( mxIsSparse(in[1]) || mxIsSparse(in[2]) ) {
mexErrMsgTxt("Input argument #2 & #3 must be of type full");
}
/* computation starts */
m = mxGetM(in[0]);
n = mxGetN(in[0]);
pr = mxGetPr(in[0]);
pi = mxGetPi(in[0]);
pir = mxGetIr(in[0]);
pjc = mxGetJc(in[0]);
i = mxGetM(in[1]);
j = mxGetN(in[1]);
xm = ((i>j)? i: j);
i = mxGetM(in[2]);
j = mxGetN(in[2]);
yn = ((i>j)? i: j);
if ( xm>0 && xm != m) {
mexErrMsgTxt("Row multiplication dimension mismatch.");
}
if ( yn>0 && yn != n) {
mexErrMsgTxt("Column multiplication dimension mismatch.");
}
nzmax = mxGetNzmax(in[0]);
cmplx = (pi==NULL ? 0 : 1);
out[0] = mxCreateSparse(m,n,nzmax,cmplx);
if (out[0]==NULL) {
mexErrMsgTxt("Not enough space for the output matrix.");
}
qr = mxGetPr(out[0]);
qi = mxGetPi(out[0]);
qir = mxGetIr(out[0]);
qjc = mxGetJc(out[0]);
/* left multiplication */
x = mxGetPr(in[1]);
if (yn==0) {
for (j=0; j<n; j++) {
qjc[j] = pjc[j];
for (k=pjc[j]; k<pjc[j+1]; k++) {
i = pir[k];
qir[k] = i;
qr[k] = x[i] * pr[k];
if (cmplx) {
qi[k] = x[i] * pi[k];
}
}
}
qjc[n] = k;
return;
}
/* right multiplication */
y = mxGetPr(in[2]);
if (xm==0) {
for (j=0; j<n; j++) {
qjc[j] = pjc[j];
for (k=pjc[j]; k<pjc[j+1]; k++) {
qir[k] = pir[k];
qr[k] = pr[k] * y[j];
if (cmplx) {
qi[k] = qi[k] * y[j];
}
}
}
qjc[n] = k;
return;
}
/* both sides */
for (j=0; j<n; j++) {
qjc[j] = pjc[j];
for (k=pjc[j]; k<pjc[j+1]; k++) {
i = pir[k];
qir[k]= i;
qr[k] = x[i] * pr[k] * y[j];
if (cmplx) {
qi[k] = x[i] * qi[k] * y[j];
}
}
qjc[n] = k;
}
}
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