Added a comment documenting numerical issues with log10factorial in A…

…lleleFractionLikelihoods.
broadinstitute · Jan 28, 2022 · fc02f7a · fc02f7a
1 parent ed84d00
commit fc02f7a
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/...java/org/broadinstitute/hellbender/tools/copynumber/models/AlleleFractionLikelihoods.java b/...java/org/broadinstitute/hellbender/tools/copynumber/models/AlleleFractionLikelihoods.java
@@ -87,6 +87,8 @@ static double hetLogLikelihood(final AlleleFractionGlobalParameters parameters,
                 - n * log(majorFraction + minorFraction * lambda0RefMinor);
         final double refMinorLogLikelihood = logNotPi + logcRefMinor + Gamma.logGamma(rhoRefMinor) - rhoRefMinor * log(tauRefMinor);
 
+        // changing the factorial implementation below may introduce non-negligible numerical differences;
+        // note https://github.com/broadinstitute/gatk/pull/7652
         final double outlierLogLikelihood = logPi + log10ToLog(log10Factorial(a) + log10Factorial(r) - log10Factorial(a + r + 1));
 
         return NaturalLogUtils.logSumExp(altMinorLogLikelihood, refMinorLogLikelihood, outlierLogLikelihood);