no its not the loop i tried changing the computation and printing the sum
the loops is definetly executed and I am also getting
*time_spent=0.000001*
ok this is insane but i found what is wrong with your code your loop is
for (long i = 1; i <= 1000000000; ++i)
but my loop is
for (int i = 0; i <= 1000000000; ++i)
no its not the long that causes the problem its the fact that you star
counting from 1
no idea why but if you start counting from 0 it reports sensible numbers in
the case of
long sum = 0;
for (long i = 0; i <= 1000000000; ++i)
{
sum = 0+i;
}
it reports the reasonable
*time_spent=0.397446*
so maybe its some optimisation it does when the counting starts from 1 not
executing the loop in its entirety ?
On Sat, Dec 17, 2016 at 6:33 PM Sven Van Caekenberghe <s...@stfx.eu> wrote:
> On 17 Dec 2016, at 15:52, Sven Van Caekenberghe <s...@stfx.eu> wrote:
>
>>
>> On 17 Dec 2016, at 15:23, Sven Van Caekenberghe <s...@stfx.eu> wrote:
>>
>>
>>> On 17 Dec 2016, at 14:28, Henrik Nergaard <henrik.nerga...@uia.no>
wrote:
>>>
>>> This is not a comparable benchmark as the sum in Smalltalk keeps on
growing and ends up doing LargeInteger calculations and thus the speed
loss, while the c the int just rolls over.
>>>
>>> Sum in Smalltalk = 500000000500000000
>>> Sum in C = -1243309312
>>
>> Yes, I realised afterwards. Shame on me.
>>
>> Now, in Pharo 64 bits:
>>
>> [
>> | sum |
>> sum:= 0.
>> 1 to: 1e9 do: [ :i | sum := sum + i ].
>> self assert: sum = (1e9 * (1e9 + 1) / 2) ] timeToRun.
>>
>> "0:00:00:03.379"
>>
>> (1e9 * (1e9 + 1) / 2) < SmallInteger maxVal.
>>
>> "true"
>>
>> So there the speed difference is way smaller.
>
> And here is a correct C99 version
>
> $ cat bench.c
> #include <stdio.h>
> #include <time.h>
> #include <assert.h>
>
> int main() {
> clock_t begin = clock();
>
> long sum = 0;
> for (int i = 1; i <= 1000000000; i++)
> sum += i;
>
> assert(sum == ((1000000000*1000000001)/2));
>
> clock_t end = clock();
> double time_spent = (double)(end - begin) / CLOCKS_PER_SEC;
> printf("time_spent=%f\n", time_spent);
> }
>
> prometheus:tmp sven$ ./a.out
> time_spent=2.393986
But,
$ cat bench.c
#include <stdio.h>
#include <time.h>
#include <assert.h>
int main() {
clock_t begin = clock();
long sum = 0L;
for (long i = 1; i <= 1000000000; i++)
sum += i;
assert(sum == ((1000000000L*1000000001L)/2L));
clock_t end = clock();
double time_spent = (double)(end - begin) / CLOCKS_PER_SEC;
printf("time_spent=%f\n", time_spent);
return (int)sum;
}
$ cc -O2 bench.c
$ ./a.out
time_spent=0.000002
Who knows what optimisation was applied ? Maybe the loop wasn't executed at
all ... (but I did add the return statement).
>>> Best regards,
>>> Henrik
>>>
>>> -----Original Message-----
>>> From: Pharo-users [mailto:pharo-users-boun...@lists.pharo.org] On
Behalf Of Sven Van Caekenberghe
>>> Sent: Saturday, December 17, 2016 2:15 PM
>>> To: Any question about pharo is welcome <pharo-users@lists.pharo.org>
>>> Subject: Re: [Pharo-users] [Stupid Benchmarks] C++ vs Pharo
>>>
>>> Like this:
>>>
>>> [ | sum | sum:= 0. 1 to: 1e9 do: [ :i | sum := sum + i ]. sum ]
timeToRun.
>>>
>>> "0:00:00:39.305"
>>>
>>> cat bench.c
>>>
>>> #include <stdio.h>
>>> #include <time.h>
>>>
>>> int main() {
>>> clock_t begin = clock();
>>>
>>> int sum = 0;
>>> for (int i = 0; i < 1000000000; i++)
>>> sum += i;
>>>
>>> clock_t end = clock();
>>> double time_spent = (double)(end - begin) / CLOCKS_PER_SEC;
>>> printf("time_spent=%f\n", time_spent); }
>>>
>>> ./a.out
>>>
>>> time_spent=2.370234
>>>
>>> That is C being 16 times faster ...
>>>
>>>> On 17 Dec 2016, at 13:49, Sven Van Caekenberghe <s...@stfx.eu> wrote:
>>>>
>>>> Hmm, this sounds wrong (C++ should be (a lot) faster on such micro
benchmarks).
>>>>
>>>> You should exclude the executable startup time.
>>>>
>>>> In Pharo you should do [ .. ] timeToRun and something similar in C/C++.
>>>>
>>>>> On 17 Dec 2016, at 13:41, Dimitris Chloupis <kilon.al...@gmail.com>
wrote:
>>>>>
>>>>> in multiplication pharo is around 2 times slower compared to C++
>>>>>
>>>>> #include <stdio.h>
>>>>>
>>>>> int main()
>>>>> {
>>>>> double x=1;
>>>>> for(double i; i<1000000000 ; ++i)
>>>>> {
>>>>> x = 0.1*i;
>>>>> }
>>>>>
>>>>> return 1;
>>>>> }
>>>>>
>>>>> time ./testMul
>>>>> 3.13 real 3.13 user 0.00 sys
>>>>>
>>>>> time ./pharo Ephestos.image eval "|x| x := 1. 1 to: 1000000000
do:[:each| x := 0.1 * each]"
>>>>> 1
>>>>> 4.97 real 4.48 user 0.09 sys
>>>>>
>>>>> On Sat, Dec 17, 2016 at 2:16 PM Dimitris Chloupis <
kilon.al...@gmail.com> wrote:
>>>>> So I was bored and decided to test how fast pharo is compared to C++.
>>>>>
>>>>> so I tested addition
>>>>>
>>>>> C++ version:
>>>>>
>>>>> #include <stdio.h>
>>>>>
>>>>> int main()
>>>>> {
>>>>> double x=0;
>>>>> while(x<1000000000)
>>>>> {
>>>>> x = x+1;
>>>>> }
>>>>>
>>>>> return 1;
>>>>> }
>>>>>
>>>>> time ./test1
>>>>> 2.84 real 2.84 user 0.00 sys
>>>>>
>>>>> Pharo version:
>>>>>
>>>>> time ./pharo Ephestos.image eval "|x| x := 0. 1 to: 1000000000
do:[:each| x := x +1]"
>>>>> 1
>>>>> 2.09 real 1.94 user 0.08 sys
>>>>>
>>>>> Pharo is +50% faster than C++ ... o_O ... that's suprising, I assume
here Pharo VM probably does some kind of optimisation.
