Optimized bytecode in exec statement

Hermann Lauer Hermann.Lauer at iwr.uni-heidelberg.de
Tue Feb 2 00:05:16 CET 2010


Dear All,

while trying to optimize some unpack operations with self compiling 
code I wondered howto invoke the optimization in the exec statement.
Even starting with -O or -OO yields in Python 2.5.2 the same dis.dis code, which
is appended below.

My interest would be to reduce the LOAD_FAST ops of "s" with DUP_TOP on the stack
(are there hash lookups behind those ?) and of course to optimize the integer
arithmetics following below (removing +-0 etc).

Thanks for any ideas,
greetings
  Hermann


>>> import dis
>>> g=r.rra.LAST3.getter(ds=0,row=0)

class fa(struct.Struct):
  def __init__(s):
    super(fa,s).__init__('d')

  def __call__(s,):
      return s.unpack_from(s.buf,5392+(((s.lastrow()-0)%2880)*3+0)*8)[0]

>>> dis.dis(g.__call__)
  7           0 LOAD_FAST                0 (s)
              3 LOAD_ATTR                0 (unpack_from)
              6 LOAD_FAST                0 (s)
              9 LOAD_ATTR                1 (buf)
             12 LOAD_CONST               1 (5392)
             15 LOAD_FAST                0 (s)
             18 LOAD_ATTR                2 (lastrow)
             21 CALL_FUNCTION            0
             24 LOAD_CONST               2 (0)
             27 BINARY_SUBTRACT     
             28 LOAD_CONST               3 (2880)
             31 BINARY_MODULO       
             32 LOAD_CONST               4 (3)
             35 BINARY_MULTIPLY     
             36 LOAD_CONST               2 (0)
             39 BINARY_ADD          
             40 LOAD_CONST               5 (8)
             43 BINARY_MULTIPLY     
             44 BINARY_ADD          
             45 CALL_FUNCTION            2
             48 LOAD_CONST               2 (0)
             51 BINARY_SUBSCR       
             52 RETURN_VALUE        


-- 
Netzwerkadministration/Zentrale Dienste, Interdiziplinaeres 
Zentrum fuer wissenschaftliches Rechnen der Universitaet Heidelberg
IWR; INF 368; 69120 Heidelberg; Tel: (06221)54-8236 Fax: -5224
Email: Hermann.Lauer at iwr.uni-heidelberg.de



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