[antlr-interest] Lexer speed comparison
tmoog at polhode.com
Wed Feb 25 17:41:40 PST 2004
a. Did you use flex -F or -f ?
b. Did you try to eliminate I/O time in some way (e.g. by parsing
from memory rather than a file) ?
c. Did the java tools time require 8-bit => 16 bit conversion or
were they 8 bit character scanners or was code conversion done
only once before the timing loop ?
d. Did you allow "warm-up" time for the jit ?
On Wed, 25 Feb 2004, Uli Bubenheimer wrote:
> I ran some tests comparing Lexers generated by different tools in
> terms of speed. The sophistication of my Lexer specification that I
> used as input for the Lexer generators is about that of a lexer for C.
> The average numbers I found by repeatedly running the generated lexers
> on a large source file were these:
> ANTLR 8300ms
> JLex 6500ms
> JFlex 1.4pre5 2000ms
> Flex 1900ms
> I used current versions of all tools. For the ANTLR comparison I had
> to adjust the Lexer specification, but tried to make it as efficient
> as possible. For the Flex comparison, I basically called Flex's
> yylex() function from Java via JNI. Also in the case of Flex I
> generated fewer Java objects as output than for the others, and if I
> take that into account, Flex's time would probably be more similar to
> I was surprised to find that ANTLR generated the slowest lexer.
> Naturally, when interpreting these numbers keep in mind that the
> outcome may have been different on a different lexer specification or
> lexer input text. On the other hand, it makes sense to me that a DFA
> would be faster on average than a more powerful recursive-descent parser.
> Are there other performance numbers available? I have not been able to
> dig up anything substantial. I also wonder how ANTLR-generated LL(k)
> parsers perform compared to LALR(1) parsers.
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