[RNG-92] LargeMeanPoissonSampler cannot handle a mean less than 1

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.3
• Fix Version/s: 1.3
• Component/s: sampling
• Assignee: Alex Herbert
• Reporter: Alex Herbert
• Created: 15/Apr/19 14:54
• Updated: 11/Nov/19 14:26
• Resolved: 15/Apr/19 15:44

Description

The LargeMeanPoissonSampler computes:

lambda = Math.floor(mean);
logLambda = Math.log(lambda);

So if the mean is less than 1 the logLambda is NaN and other precomputed factors are based on a lambda of zero. This results in infinite loop within the sampler method.

Fix by removing support for a mean less than 1.