Speeding up LEX scanning times

I'm writing a Cobol parser, using MKS Lex and Yacc. So far so good.
However, on seriously large programs, it is quite slow. When I profiled
the code, I noticed that about 80% of the time was in the Lex scanner.
Now, I found that the standard C functions for file access (fread) are
a lot slower than the non-standard read functions, so I shaved off
some time by using these if the compiler supports them.


However, I still find that the scanner is slow. I don't think I made
any mistakes; for instance all keywords are identified by looking-up
a table, rather than as individual scanner tokens.


So my question is: should I consider writing the scanner by hand,
now that I have a working prototype? If so, are there any techniques
I should be aware of?


--
Pieter A. Hintjens
[I believe that flex is a lot faster than other versions of lex. Try that.
-John]
--

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