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#include "find_peaks.h"
#include "vector.h"
#include "event.h"
#include "pmt.h"
#include <stddef.h> /* for size_t */
#include <stdlib.h> /* for malloc() */
#include "optics.h"
#include <math.h> /* for exp() */
typedef struct peak {
size_t i;
size_t j;
double value;
} peak;
/* Compare two different peaks.
*
* Note: We return 1 if peak b is greater than peak b and -1 if peak a is
* greater than peak b. This is backwards from what you would normally expect,
* but it's because we want to keep the peaks sorted in *descending* order. */
static int peak_compare(const void *a, const void *b)
{
const peak *pa = (peak *) a;
const peak *pb = (peak *) b;
if (pa->value > pb->value)
return -1;
else if (pa->value < pb->value)
return 1;
return 0;
}
void find_peaks_array(double *x, size_t n, size_t m, size_t *imax, size_t *jmax, size_t *npeaks, size_t max_peaks, double threshold)
{
/* Find a maximum of `max_peaks` in the 2D array `x` indexed as:
*
* x[i,j] = x[i*m + j]
*
* and store the indices in the two arrays `imax` and `jmax`.
*
* Peaks are defined as any array element which is greater than all 8 of
* it's neighbors. Peaks are also required to be at least max*threshold
* times as high as the highest peak.
*
* The returned peaks will always be the *highest* peaks and they will be
* returned in sorted order from highest to lowest. */
size_t i, j;
double max;
peak *p;
if (n*m == 0) {
*npeaks = 0;
return;
}
p = malloc(sizeof(peak)*(max_peaks+1));
/* First, find the highest value in the array (which is guaranteed to be a peak). */
max = x[0];
p[0].i = 0;
p[0].j = 0;
p[0].value = max;
for (i = 0; i < n; i++) {
for (j = 0; j < m; j++) {
if (x[i*m + j] > max) {
max = x[i*m + j];
p[0].i = i;
p[0].j = j;
p[0].value = max;
}
}
}
*npeaks = 1;
if (*npeaks >= max_peaks) goto end;
/* Now we look for other peaks which are at least max*threshold high. */
for (i = 0; i < n; i++) {
for (j = 0; j < m; j++) {
if (x[i*m + j] <= max*threshold) continue;
if (i == p[0].i && j == p[0].j) continue;
/* Check to see if it is actually a peak. */
if (x[i*m + (j+1) % m] < x[i*m + j] && /* 0 +1 */
x[i*m + (j+m-1) % m] < x[i*m + j] && /* 0 -1 */
x[((i+1) % n)*m + j] < x[i*m + j] && /* +1 0 */
x[((i+1) % n)*m + (j+1) % m] < x[i*m + j] && /* +1 +1 */
x[((i+1) % n)*m + (j+m-1) % m] < x[i*m + j] && /* +1 -1 */
x[((i+n-1) % n)*m + j] < x[i*m + j] && /* -1 0 */
x[((i+n-1) % n)*m + (j+1) % m] < x[i*m + j] && /* -1 +1 */
x[((i+n-1) % n)*m + (j+m-1) % m] < x[i*m + j]) { /* -1 -1 */
p[*npeaks].i = i;
p[*npeaks].j = j;
p[*npeaks].value = x[i*m+j];
*npeaks += 1;
qsort(p,*npeaks,sizeof(peak),peak_compare);
if (*npeaks >= max_peaks) *npeaks = max_peaks;
}
}
}
end:
for (i = 0; i < *npeaks; i++) {
imax[i] = p[i].i;
jmax[i] = p[i].j;
}
free(p);
return;
}
void get_hough_transform(event *ev, double *pos, double *x, double *y, size_t n, size_t m, double *result)
{
/* Computes the "Hough transform" of the event `ev` and stores it in `result`. */
size_t i, j, k;
double dir[3], pmt_dir[3], cos_theta;
double wavelength0 = 400.0;
double n_d2o = get_index_snoman_d2o(wavelength0);
for (i = 0; i < MAX_PMTS; i++) {
if (pmts[i].pmt_type != PMT_NORMAL || !ev->pmt_hits[i].hit) continue;
SUB(pmt_dir,pmts[i].pos,pos);
normalize(pmt_dir);
for (j = 0; j < n; j++) {
for (k = 0; k < m; k++) {
double r = 1+x[j]*x[j]+y[k]*y[k];
dir[0] = 2*x[j]/r;
dir[1] = 2*y[k]/r;
dir[2] = (-1+x[j]*x[j]+y[k]*y[k])/r;
cos_theta = DOT(pmt_dir,dir);
result[j*m + k] += ev->pmt_hits[i].qhs*exp(-fabs(cos_theta-1.0/n_d2o)/0.1);
}
}
}
}
void find_peaks(event *ev, double *pos, size_t n, size_t m, double *peak_theta, double *peak_phi, size_t *npeaks, size_t max_peaks, double threshold)
{
size_t i;
double *x = calloc(n,sizeof(double));
double *y = calloc(m,sizeof(double));
double *result = calloc(n*m,sizeof(double));
for (i = 0; i < n; i++) {
x[i] = -10 + 20.0*i/(n-1);
}
for (i = 0; i < m; i++) {
y[i] = -10 + 20.0*i/(m-1);
}
get_hough_transform(ev,pos,x,y,n,m,result);
size_t *imax = calloc(max_peaks,sizeof(size_t));
size_t *jmax = calloc(max_peaks,sizeof(size_t));
find_peaks_array(result,n,m,imax,jmax,npeaks,max_peaks,threshold);
for (i = 0; i < *npeaks; i++) {
double R, theta;
R = sqrt(x[imax[i]]*x[imax[i]]+y[jmax[i]]*y[jmax[i]]);
theta = atan2(y[jmax[i]],x[imax[i]]);
peak_theta[i] = 2*atan(1/R);
peak_phi[i] = theta;
}
free(imax);
free(jmax);
free(x);
free(y);
free(result);
}
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