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/* This is based on
http://www.mathworks.com/access/helpdesk/help/techdoc/matlab_external/ch04cr12.shtml
See rectintSparse.m for the matlab version of this code.
*/
#include <math.h> /* Needed for the ceil() prototype. */
#include "mex.h"
#include <stdio.h>
/* If you are using a compiler that equates NaN to be zero, you
* must compile this example using the flag -DNAN_EQUALS_ZERO.
* For example:
*
* mex -DNAN_EQUALS_ZERO fulltosparse.c
*
* This will correctly define the IsNonZero macro for your C
* compiler.
*/
#if defined(NAN_EQUALS_ZERO)
#define IsNonZero(d) ((d) != 0.0 || mxIsNaN(d))
#else
#define IsNonZero(d) ((d) != 0.0)
#endif
#define MAX(x,y) ((x)>(y) ? (x) : (y))
#define MIN(x,y) ((x)<(y) ? (x) : (y))
void mexFunction(
int nlhs, mxArray *plhs[],
int nrhs, const mxArray *prhs[]
)
{
/* Declare variables. */
int j,k,m,n,nzmax,*irs,*jcs, *irs2, *jcs2;
double *overlap, *overlap2, tmp, areaA, areaB;
double percent_sparse;
double *leftA, *rightA, *topA, *bottomA;
double *leftB, *rightB, *topB, *bottomB;
double *verbose;
/* Get the size and pointers to input data. */
m = MAX(mxGetM(prhs[0]), mxGetN(prhs[0]));
n = MAX(mxGetM(prhs[4]), mxGetN(prhs[4]));
/* printf("A=%d, B=%d\n", m, n); */
leftA = mxGetPr(prhs[0]);
rightA = mxGetPr(prhs[1]);
topA = mxGetPr(prhs[2]);
bottomA = mxGetPr(prhs[3]);
leftB = mxGetPr(prhs[4]);
rightB = mxGetPr(prhs[5]);
topB = mxGetPr(prhs[6]);
bottomB = mxGetPr(prhs[7]);
verbose = mxGetPr(prhs[8]);
/* Allocate space for sparse matrix.
* NOTE: Assume at most 20% of the data is sparse. Use ceil
* to cause it to round up.
*/
percent_sparse = 0.01;
nzmax = (int)ceil((double)m*(double)n*percent_sparse);
plhs[0] = mxCreateSparse(m,n,nzmax,0);
overlap = mxGetPr(plhs[0]);
irs = mxGetIr(plhs[0]);
jcs = mxGetJc(plhs[0]);
plhs[1] = mxCreateSparse(m,n,nzmax,0);
overlap2 = mxGetPr(plhs[1]);
irs2 = mxGetIr(plhs[1]);
jcs2 = mxGetJc(plhs[1]);
/* Assign nonzeros. */
k = 0;
for (j = 0; (j < n); j++) {
int i;
jcs[j] = k;
jcs2[j] = k;
for (i = 0; (i < m); i++) {
tmp = (MAX(0, MIN(rightA[i], rightB[j]) - MAX(leftA[i], leftB[j]) )) *
(MAX(0, MIN(topA[i], topB[j]) - MAX(bottomA[i], bottomB[j]) ));
if (*verbose) {
printf("j=%d,i=%d,tmp=%5.3f\n", j,i,tmp);
}
if (IsNonZero(tmp)) {
/* Check to see if non-zero element will fit in
* allocated output array. If not, increase
* percent_sparse by 20%, recalculate nzmax, and augment
* the sparse array.
*/
if (k >= nzmax) {
int oldnzmax = nzmax;
percent_sparse += 0.2;
nzmax = (int)ceil((double)m*(double)n*percent_sparse);
/* Make sure nzmax increases atleast by 1. */
if (oldnzmax == nzmax)
nzmax++;
printf("reallocating from %d to %d\n", oldnzmax, nzmax);
mxSetNzmax(plhs[0], nzmax);
mxSetPr(plhs[0], mxRealloc(overlap, nzmax*sizeof(double)));
mxSetIr(plhs[0], mxRealloc(irs, nzmax*sizeof(int)));
overlap = mxGetPr(plhs[0]);
irs = mxGetIr(plhs[0]);
mxSetNzmax(plhs[1], nzmax);
mxSetPr(plhs[1], mxRealloc(overlap2, nzmax*sizeof(double)));
mxSetIr(plhs[1], mxRealloc(irs2, nzmax*sizeof(int)));
overlap2 = mxGetPr(plhs[1]);
irs2 = mxGetIr(plhs[1]);
}
overlap[k] = tmp;
irs[k] = i;
areaA = (rightA[i]-leftA[i])*(topA[i]-bottomA[i]);
areaB = (rightB[j]-leftB[j])*(topB[j]-bottomB[j]);
overlap2[k] = MIN(tmp/areaA, tmp/areaB);
irs2[k] = i;
k++;
} /* IsNonZero */
} /* for i */
}
jcs[n] = k;
jcs2[n] = k;
}
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