[erlang-questions] Why erlang's computing performance is enormously less than c++

[谈广云]

can you tell me why the native flag can cause such improvement?


the way that add natvie flag is not the bese ,since it is not in safe mode,.


is there anyother Available way？







At 2016-11-11 21:10:10, "Tony Rogvall" <tony@REDACTED> wrote:
>The original program is looping over [1,2,3,4] when it should loop over [1,2,3,4,5] as
>in the C program. After fixing that and also making sure the program is using floating point
>numbers and adding a variable that calculate a result, then the difference is  ( on my mac )
>
>Erlang: 57s
>C: 3.7s
>
>That is 15 times slower which is not that bad considering :-)
>But when adding a -O3 flag to the C code compilation that ratio will increases to 110 times slower.
>Just tossing in a -native flag did not lead to a any significant change but…
>The when using the still forgotten loop unrolling directives, inline sizes and friends.
>I used this ( WARNING! not to be used in production code yet, I guess? )
>
>-compile(native).
>-compile(inline).
>-compile({inline_size,1000}).
>-compile({inline_effort,2000}).
>-compile({inline_unroll,6}).
>
>Erlang: 4.3s
>
>Which is nearly the same as unoptimized C code and
>just 8 times slower than -O3 optimized C code.
>and that is just amazing!
>
>/Tony
>
>> On 11 nov 2016, at 11:13, Richard Carlsson <carlsson.richard@REDACTED> wrote:
>> 
>> You are comparing a native-compiled C++ program that works on small arrays of raw numbers with an interpreted Erlang program that traverses linked lists of tagged numbers. The only surprise is that the difference is _only_ a factor 10. (And if the C code was using integers instead of double precision floats, it would be even faster.)
>> 
>> 
>>         /Richard
>> 
>> 2016-11-11 8:26 GMT+01:00 谈广云 <fw339tgy@REDACTED>:
>> i campare the erlang's computing with c++
>> 
>> erlang run 100000000 time the test_sum_0
>> 
>> test_sum_0(N) ->
>>   bp_eva_delta([1,2,3,4],[3,4,5,6],[]),
>>   test_sum_0(N-1).
>> 
>> 
>> bp_eva_delta([],_,L) ->
>> 	lists:reverse(L);
>> bp_eva_delta([O|Output],[S|Sigma],L) ->
>> 	bp_eva_delta(Output,Sigma,[S * O * (1-O) |L]).
>> 
>> 
>> 
>> 
>> c++ run the same time (100000000 ) the similar fun ,
>> 
>> for(int i = 0 ;i< 100000000;++i)
>> 	{
>> 		double b[5] = {1,2,3,4,5};
>> 		double s[5] = {6,7,8,9,10};
>> 		double o[5];
>> 		for(int i = 0; i < 5;++i)
>> 		{
>> 			o[i] = s[i] * b[i] * (1 - b[i]);
>> 		}
>> 
>> 	}.
>> 
>> the erlang spend 29's , and c++ spend 2.78's.
>> 
>> why the erlang is so slower than c++?
>> 
>>  Or I do not configure  the right parameter?
>> 
>> 
>> 
>> 
>> 
>> 
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