Description
It appears that the EPL implementation effectively does a nested loop over all types in the patter. Although this will effectively construct all tuples, for the EMG case it results in a tendency to satisfy generation patterns with the first elements of the type of the outer loop, as opposed to randomly selected tuples from the complete set of type tuples.
What would be desirable for EMG is that the tuples are visited randomly.
For this a random sequence of indexes for access can be generated for each type in the pattern.
To avoid that the first element of the first collection is matched against all the other collections visiting the sequences of indexes should be done randomly to. For this, a generator of valid index combinations can be created. The generator guarantees that all possible combinations are tried, but visits them in random order.