Explorations en terre animale

Speeding up MadGraph5_aMC@NLO

“…Since the convergence rate is fixed to 1 √ N , the various avenues of optimisation consist in modifying the function being integrated to effectively reduce its variance. In MG5aMC, we use the single diagram enhancement method [29], which combines various importance sampling method -both analytical [42] and numerical [43,44]-on top of a multi-channel strategy. The integral is decomposed as a sum of various contributions:…”

“…In other words, with this choice the assumption is that each of the terms of the sum -called channels of integration-are mainly behaving as a single diagram squared from which the poles are easily identifiable and importance sampling is relatively easy to implement (see section (3.2)). The role of machine learning algorithm (MG5aMC use a modified VEGAS algorithm [43]) is then mainly to catch the impact of…”

“…( 31) creates correlations between the variables of integration. Such type of correlation are problematic for any type of VEGAS-like algorithm [42,43]. The importance of the ordering can be seen in figure (4) where we compare various orderings for a given channel of integration (the associated diagram is displayed in the figure).…”