On Tue, Nov 29, 2005 at 09:48:15AM +0100, David Siroky wrote: > Hi!
>
> I need to enlighten myself in Python unicode speed and implementation.
>
> My platform is AMD Athlon@1300 (x86-32), Debian, Python 2.4.
>
> First a simple example (and time results):
>
> x = "a"*50000000
> real 0m0.195s
> user 0m0.144s
> sys 0m0.046s
>
> x = u"a"*50000000
> real 0m2.477s
> user 0m2.119s
> sys 0m0.225s
>
> So my first question is why creation of a unicode string lasts more then 10x
> longer than non-unicode string?
string objects have the optimization described in the log message below.
The same optimization hasn't been made to unicode_repeat, though it would
probably also benefit from it.
Christian Tismer pointed out the high cost of the loop overhead and
function call overhead for 'c' * n where n is large. Accordingly,
the new code only makes lg2(n) loops.
Interestingly, 'c' * 1000 * 1000 ran a bit faster with old code. At some
point, the loop and function call overhead became cheaper than invalidating
the cache with lengthy memcpys. But for more typical sizes of n, the new
code runs much faster and for larger values of n it runs only a bit slower.
------------------------------------------------------------------------
If you're a "C" coder too, consider creating and submitting a patch to do this
to the patch tracker on http://sf.net/projects/python . That's the best thing
you can do to ensure the optimization is considered for a future release of
Python.
Re: Assembly string functions in i386 libc ... of string functions on i386? ... for the usual overhead for string instructions). ... The cmpb in this takes 2 cycles, but the loop overhead takes no more ... versions using the string instructions are much ... (freebsd-arch)
extension_pack ... It is used to set upper loop -- limits for non-deterministic values thus avoiding the use of access -- types and enabling the functions to be used for synthesizeable code. ... DivisorVal: integer) return std_logic_vector; function "/"(DividendVal: string; DivisorVal: integer) return std_logic_vector; ... for loopVar in 0 to slvVal'length/4-1 loop ... end loop; if then return not resultVar; -- "width mismatch" errors here are due to improper sizing of the vector that this function is assigned to else return resultVar; -- "width mismatch" errors here are due to improper sizing of the vector that this function is assigned to end if; ... (comp.lang.vhdl)
extension_pack ... It is used to set upper loop -- limits for non-deterministic values thus avoiding the use of access -- types and enabling the functions to be used for synthesizeable code. ... DivisorVal: integer) return std_logic_vector; function "/"(DividendVal: string; DivisorVal: integer) return std_logic_vector; ... for loopVar in 0 to slvVal'length/4-1 loop ... end loop; if then return not resultVar; -- "width mismatch" errors here are due to improper sizing of the vector that this function is assigned to else return resultVar; -- "width mismatch" errors here are due to improper sizing of the vector that this function is assigned to end if; ... (comp.lang.vhdl)
extension_pack ... It is used to set upper loop -- limits for non-deterministic values thus avoiding the use of access -- types and enabling the functions to be used for synthesizeable code. ... DivisorVal: integer) return std_logic_vector; function "/"(DividendVal: string; DivisorVal: integer) return std_logic_vector; ... for loopVar in 0 to slvVal'length/4-1 loop ... end loop; if then return not resultVar; -- "width mismatch" errors here are due to improper sizing of the vector that this function is assigned to else return resultVar; -- "width mismatch" errors here are due to improper sizing of the vector that this function is assigned to end if; ... (comp.lang.vhdl)
extension_pack ... It is used to set upper loop -- limits for non-deterministic values thus avoiding the use of access -- types and enabling the functions to be used for synthesizeable code. ... DivisorVal: integer) return std_logic_vector; function "/"(DividendVal: string; DivisorVal: integer) return std_logic_vector; ... for loopVar in 0 to slvVal'length/4-1 loop ... end loop; if then return not resultVar; -- "width mismatch" errors here are due to improper sizing of the vector that this function is assigned to else return resultVar; -- "width mismatch" errors here are due to improper sizing of the vector that this function is assigned to end if; ... (comp.lang.vhdl)
