Commits (2)

Prior to this change, given two records of weight 1 the algorithm would return them in the order (0,1) with 100% probability instead of the desired 50%. This was due to an offbyone error in the range test. srv_rand() returns a float in the range [0.0, 1.0[, so r is an integer in the range [0, total[. The correct probability for record 0 to be chosen is a[0].weight/total, not (a[0].weight+1)/total.
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The fallback to a straight FisherYates shuffle needs to occur whenever the sum of the *remaining* weights is zero, or else the remaining records will not be reordered. Testing only once at the beginning covers the case when all weights are zero, and obviously no shuffling is needed when only one weight is zero; but other weight combinations are possible, such as (1, 0, 0).
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