[antlr-interest] Perfomance question re bit iterator

[ron_bennatan]

Hi,

We have fairly complex parsers with some (but not too much) 
loookahead. We generate C++ code and we use codeGenBitsetThreshold=4.

We've been doing some performance testing and when running gprof we 
see that around 40% of the time is in MismatchTokenException and 
specifically in std::_Bit_iterator std::_copy. 

Can anyone shed some light as to what exactly MismatchTokenException 
is, when it is raised (we think we know - but are not sure) and what 
we can do to reduce the run time? Also, are there any tips as to how 
to reduce the number of copies and anything else that can reduce the 
number of these exceptions and copies.

Thanks.








 
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