pyparsing性能和內存使用

Question

Pyparsing運行良好的一個非常小的語法，但語法的不斷壯大，性能下降，並通過屋頂的內存使用情況。

我現在gramar是：

newline = LineEnd() 
minus = Literal ('-') 
plus = Literal ('+') 
star = Literal ('*') 
dash = Literal ('/') 
dashdash = Literal ('//') 
percent = Literal ('%') 
starstar = Literal ('**') 
lparen = Literal ('(') 
rparen = Literal (')') 
dot = Literal ('.') 
comma = Literal (',') 
eq = Literal ('=') 
eqeq = Literal ('==') 
lt = Literal ('<') 
gt = Literal ('>') 
le = Literal ('<=') 
ge = Literal ('>=') 
not_ = Keyword ('not') 
and_ = Keyword ('and') 
or_ = Keyword ('or') 
ident = Word (alphas) 
integer = Word (nums) 

expr = Forward() 
parenthized = Group (lparen + expr + rparen) 
trailer = (dot + ident) 
atom = ident | integer | parenthized 
factor = Forward() 
power = atom + ZeroOrMore (trailer) + Optional (starstar + factor) 
factor << (ZeroOrMore (minus | plus) + power) 
term = ZeroOrMore (factor + (star | dashdash | dash | percent)) + factor 
arith = ZeroOrMore (term + (minus | plus)) + term 
comp = ZeroOrMore (arith + (eqeq | le | ge | lt | gt)) + arith 
boolNot = ZeroOrMore (not_) + comp 
boolAnd = ZeroOrMore (boolNot + and_) + boolNot 
boolOr = ZeroOrMore (boolAnd + or_) + boolAnd 
match = ZeroOrMore (ident + eq) + boolOr 
expr << match 
statement = expr + newline 
program = OneOrMore (statement) 

當我解析以下

print (program.parseString ('3*(1+2*3*(4+5))\n')) 

這需要相當長的：

~/Desktop/m2/pyp$ time python3 slow.py 
['3', '*', ['(', '1', '+', '2', '*', '3', '*', ['(', '4', '+', '5', ')'], ')']] 

real 0m27.280s 
user 0m25.844s 
sys 0m1.364s 

而且內存使用量上升到1.7吉布（原文如此！）。

有我做了一些嚴重的錯誤執行這一語法還是我還能如何保持內存使用情況在可以忍受的利潤率？

Answer 1

進口pyparsing使packrat解析到memoize的解析行爲後：

ParserElement.enablePackrat() 

這應該使性能有了很大的改進。