CHM_r* CHM_rd::rprod_SP(CHM_SP Ut) {
static double one[] = {1,0}, zero[] = {0,0};
CHM_rd *ans =
new CHM_rd(M_cholmod_allocate_dense(Ut->nrow, A->ncol,
Ut->nrow, CHOLMOD_REAL, &c));
M_cholmod_sdmult(Ut, 0/*no transpose*/, one, zero, A, ans->A, &c);
return ans;
}
CHM_r* CHM_rd::AtA() {
static double one[] = {1,0}, zero[] = {0,0};
int nc = (int)A->ncol, nr = (int)A->nrow;
CHM_rd *ans = new CHM_rd(M_cholmod_allocate_dense(nc, nc, nc,
CHOLMOD_REAL, &c));
if (nc > 0 && nr > 0)
F77_CALL(dsyrk)("U", "T", &nc, &nr, one, (double*)A->x, &nr,
zero, (double*)((ans->A)->x), &nc);
return ans;
}
/* Extract dense block x[p,q] of sparse matrix x */
CHM_DN densesubmatrix(CHM_SP x, int *p, int np, int *q, int nq, cholmod_common *c){
CHM_DN ans = M_cholmod_allocate_dense(np,nq,np,CHOLMOD_REAL,c);
double *w = malloc(x->nrow*sizeof(double));
int *xi=x->i;
int *xp=x->p;
double *xx=x->x;
double *ansx=ans->x;
int col, row;
for(int j=0;j<nq;j++){
col=q[j];
/* scatter x[:,col] over w */
for(int i=xp[col];i<xp[col+1];i++){
w[xi[i]]=xx[i];
}
/* Copy w[p] to ans[:,col] */
for(int i=j;i<np;i++){
row=p[i];
ansx[i+j*np]=w[row];
}
}
free(w);
return ans;
}
