speed up likelihood function and switch to using fixed dx

This commit speeds up the likelihood function by about ~20% by using the
precomputed track positions, directions, times, etc. instead of interpolating
them on the fly.

It also switches to computing the number of points to integrate along the track
by dividing the track length by a specified distance, currently set to 1 cm.
This should hopefully speed things up for lower energies and result in more
stable fits at high energies.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/fit.c b/src/fit.c
index 2b9652a..6ac97f1 100644
--- a/src/fit.c
+++ b/src/fit.c
@@ -38,7 +38,7 @@ static size_t iter;
 
 typedef struct fitParams {
     event *ev;
-    int n;
+    double dx;
     int fast;
     int print;
     int id;
@@ -5003,7 +5003,7 @@ double nll(unsigned int n, const double *x, double *grad, void *params)
     z2[0] = x[8];
 
     gettimeofday(&tv_start, NULL);
-    fval = nll_muon(fpars->ev, fpars->id, T, pos, dir, t0, z1, z2, 1, fpars->n, fpars->fast);
+    fval = nll_muon(fpars->ev, fpars->id, T, pos, dir, t0, z1, z2, 1, fpars->dx, fpars->fast);
     gettimeofday(&tv_stop, NULL);
 
     long long elapsed = (tv_stop.tv_sec - tv_start.tv_sec)*1000 + (tv_stop.tv_usec - tv_start.tv_usec)/1000;
@@ -5211,7 +5211,7 @@ int fit_event(event *ev, double *xopt, double *fmin, int id)
      * faster, we set the absolute tolerance on the likelihood to 1.0, the
      * maximum number of function evaluations to 100, and the relative
      * tolerance on the numerical integration to 10%. */
-    fpars.n = 100;
+    fpars.dx = 1.0;
     fpars.fast = 1;
     fpars.print = 0;
     nlopt_set_ftol_abs(opt, 1.0);
@@ -5304,7 +5304,7 @@ int fit_event(event *ev, double *xopt, double *fmin, int id)
     nlopt_set_upper_bounds(opt, ub);
 
     /* Now, we do the "real" minimization. */
-    fpars.n = 500;
+    fpars.dx = 1.0;
     fpars.fast = 0;
     fpars.print = 1;
     nlopt_set_ftol_abs(opt, 1e-5);