speed things up by introducing a minimum ratio between probabilities

Previously to avoid computing P(q,t|n)*P(n|mu) for large n when they were very
unlikely I was using a precomputed maximum n value based only on the expected
number of PE. However, this didn't take into account P(q|n).

This commit updates the likelihood function to dynamically decide when to quit
computing these probabilities when the probability for a given n divided by the
most likely probability is less than some threshold.

This threshold is currently set to 10**(-10) which means we quit calculating
these probabilities when the probability is 10 million times less likely than
the most probable value.

1 files changed, 7 insertions, 1 deletions

diff --git a/src/likelihood.h b/src/likelihood.h
index 8ddaf2a..0da7db9 100644
--- a/src/likelihood.h
+++ b/src/likelihood.h
@@ -10,7 +10,13 @@
  *
  * Note: This must be less than MAX_PE. */
 #define MAX_PE_NO_HIT 10
-#define STD_MAX 10
+
+/* To speed things up we quit calculating the probability of a hit when the
+ * ratio between the current probability and the maximum probability is less
+ * than 10**(-MIN_RATIO). So if MIN_RATIO is -10, that means that we ignore
+ * probabilities which are 10 million times less likely than the most probable
+ * value for n. */
+#define MIN_RATIO -10
 
 #define CHARGE_FRACTION 60000.0
 #define DARK_RATE 500.0