[erlang-questions] map over bitstring

[Morten Krogh]

Yes, Tony.

Now binary comprehension is 16 faster than the matching function.

So the slow part is that it has to get back to the shell and get the 
<<"b">> (which is silly in this case because it is constant).


cheers,

Morten.


On 10/22/10 1:16 PM, Tony Rogvall wrote:
>
> On 22 okt 2010, at 11.25, Morten Krogh wrote:
>
>>
>> To my enormous surprise, this program is about 7 times faster than 
>> the binary comprehension.
>>
>>
>> 18>  A = binary:copy(<<"a">>, 10000000).
>>
>> 10 MB, that is.
>>
>>
>> 19> T1 = now(), B = << <<"b">> || <<Y>> <= A>>, T2 = now(), 
>> timer:now_diff(T2,T1).
>> 68860012
>>
> Interpreted code !!!  Put this code in  a module and compile it, then 
> try again.
>
>> 22> f(T1), f(T2), f(B).
>> ok
>> 23> T1 = now(), B = zip2:map(fun(X) -> 98 end, A), T2 = now(), 
>> timer:now_diff(T2,T1).
>> 9284114
>>
> I guess zip2 is compiled.
>
>> (zip2 is my module name for this test)
>>
>>
>> What is going on?
>>
> There is a big speed difference between interpreted code and compiled 
> code.
>
> /Tony
>
> /"Have run Make so many times I dunno what's installed anymore"/
>