系統技術非業餘研究 » leex文法分析的效率
阿新 • • 發佈:2018-12-31
R13B新新增的leex相當於c的lex, 在做文法分析非常方便,但是效率如何呢? leex的example裡面帶了個erlang_scan和erlang標準的釋出版的erl_scan相容,所以我們來對比測試下效率。
注意用R13B03,因為R13B02的erlc漏掉了編譯xrl格式。
以下是實驗:
[email protected]:~# git clone git://github.com/rvirding/leex.git [email protected]:~# cd leex/examples/ [email protected]:~/leex/examples# cat test_scan.erl
-module(test_scan). -export([start/1]). start([A])-> {ok, F} = file:open(atom_to_list(?MODULE)++".erl", [read]), {ok, S} = file:read(F, 9999999), file:close(F), N = list_to_integer(A), test(N, fun erlang_scan:string/1, S, "erlang_scan"), test(N, fun erl_scan:string/1, S, "erl_scan"), ok. test(N, F, S, Ts)-> Start = erlang:now(), dotimes(N, fun (_) -> F(S) end), io:format("~s run ~w ms~n", [Ts,round(timer:now_diff(now(), Start) /1000)]). dotimes(0, _) -> done; dotimes(N, F) -> F(N), dotimes(N - 1, F).
[email protected]:~/leex/examples# erlc erlang_scan.xrl [email protected]:~/leex/examples# ls *.erl erlang_scan.erl test_scan.erl [email protected]:~/leex/examples# erlc *.erl [email protected]:~/leex/examples# erl -noshell -run test_scan start 10000 -s erlang halt erlang_scan run 2208 ms erl_scan run 1181 ms
%% 這個版本稍微慢點
[email protected]:~/leex/examples# erlc +native *.erl [email protected]:~/leex/examples# erl -noshell -run test_scan start 10000 -s erlang halt erlang_scan run 1292 ms erl_scan run 1238 ms
結論是: leex產生的程式碼和手寫的效率幾乎差不多。
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