Severe performance regression in 1.8.6

[joankaradimov]

I'm running this grammar:
https://github.com/joankaradimov/Magnetar/blob/master/MagnetarCraft/src/iscript_parser.cpp#L71
... with this input file:
https://raw.githubusercontent.com/neivv/aice/master/test_scripts/vanilla.txt

On v1.8.5 I'm observing parse times of below 1 second. On 1.8.6 it's above 10 seconds.

Similarly -- on the web playgound I was running identical examples for under 150 ms the previous week. I'm assuming the version over there was updated these last couple of days, since the execution times are suddenly 1-2 orders of magnitude worse.

[yhirose]

@joankaradimov I guess this commit causes this problem. I'll take a look at it some time this weekend. Thanks for catching the serious problem!

[joankaradimov]

In that case I think it might be this line. There are multiple std::string constructors being called within a while loop. This line can easily be moved outside the loop. And then the additional std::string allocations can be avoided altogether in the non-case-insensitive case.

This improves the situation a little bit, but it does not resolve it completely. The performance is still worse than 1.8.5.

A much better solution would be to get rid of the ignore_case_ checks in match and tweak the dictionary in the trie...

std::map<std::string, Info, std::less<>> dic_;

... to use case-insensitive comparisons instead of std::less when necessary.

[yhirose]

@joankaradimov could you check performance with the latest peglib.h in the master branch? If you confirm that it fixes the performance regression, I'll bump the version to 1.8.8. Thanks!

[joankaradimov]

@yhirose I can confirm the problem is fixed.

From ~10 seconds previously down to below 50 ms now.

[yhirose]

It's now included in v1.8.8. Thanks for your fine contribution!

[joankaradimov]

Thank you for the quick responses and fixes!

[davemcatcisco]

@yhirose - Thanks for this. Are you responsible for the vcpkg? That's still sitting at 1.8.6.

[yhirose]

@joankaradimov no. I don't know who are working on vcpkg, or other package managers like conan.