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Add support for token weights during fuzzing - #206
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Matthew Parkinson (mjp41) merged 9 commits intoOct 2, 2026
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| [&](const Token& t) { | ||
| return static_cast<double>(weight_for(t)); | ||
| }); | ||
| return choose_weighted(tokens, std::move(offsets), parent, depth); |
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Probably doesn't mater, but I wonder if some of the calculation of weights for wf entry should be done once. My quick reading of this implies you calculate the cumulative distribution each time you select an element?
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Good catch! Adressed in new (force pushed) version
Elias Castegren (EliasC)
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| std::partial_sum(offsets.begin(), offsets.end(), offsets.begin()); | ||
| return choose_from_cumulative(tokens, offsets, parent, depth); |
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Very minor bit, here you rewrite the offsets vector to a cumulative vector in place. That it keeps the same name was slightly confusing to me.
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This PR adds support for supplying token weights to the fuzzer. The weights are supplied as a map from tokens to integers and unmapped tokens defaults to 1. The driver CLI has been extended:
Note that setting a weight to zero may cause generation to abort with an exception if there is no viable option for a choice. I thought about checking for that up front (either checking for paths in the WF spec that lead to dead choices, or propagating dead choices upwards so that the path cannot happen), but I think the benefit doesn't outweigh the benefits in this case.
A possible future thing to add would be an automatic tuning of the weights based on the patterns of a pass: if the patterns have
In(Foo)andT(Bar)that suggests that we should increase the weights ofFooandBar. Preliminary experiments suggests that this reduces the number of trivial trees (trees that do not match a single rule).