On 2/1/2010 6:05 PM, Hermann Lauer wrote:
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.
Currently, as far as I know, -0 just removes asserts.
My interest would be to reduce the LOAD_FAST ops of "s" with DUP_TOP on the
stack
(are there hash lookups behind those ?)
Load_fast is a locals array lookup. load_fast 0 (s) means "put
locals[0] on the top of the stack". The '(s)' is added for the human reader.
and of course to optimize the integer
arithmetics following below (removing +-0 etc).
Something + 0 is no necessarily something. It depends on the type of
something. So the interpreter will not optimize it away. What concretely
happens with int+0 is a different matter. You can remove it though, if
you want to get into byte-code hacking, but why write '+0' if you do not
want it?
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
Terry Jan Reedy
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