Make grammar immutable #469
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I also changed the benchmarks slightly to move the initialization code out of the hot path so the results only focus on what matters. And returned the resulting expression such that the compiler would not optimize the method as the result is not used (it is not but it's a best practice for BDN usage). |
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Are the tests flaky? I don't even get the same failing ones locally. I can already see a problem due to timezones, but I don't get why the others are different. |
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Thank you very much for this! Yes that 1 test fails sometimes. I need to track down why - it includes all the fields just a different order, which typing this out actually might make sense depending on how tests run and I should check it with regardless of order. |
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This is the flamegraph before the fix. I could see that all the time was spent in creating parse nodes and initializing their structures (ToDictionary, CharMap, ...). This is not normal, this should be done once. This meant that the parsers were begin constructed too often. The parser should be a singleton, unless some grammars vary in terms of syntax, but not behavior.
The solution is to incorporate the
ParseContextwhich is specific to each invocation. And the parser lambdas can use it. This way the parser can be static. I used a localInstancefield but I usually create my own static parser instance that I reuse. Totally fine how I did it here. Makes it more obvious for the future.