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Re: time command does not show CPU time for MinGW binaries




On 1/7/2018 10:38 AM, daniel@xxxxxxxxxxxxxxxxxxxxxxx wrote:
> time command does not show CPU time for MinGW binaries. I have this
> sample piece of code:
> 
> #include <stdio.h>
> #include <time.h>
> 
> #define N 100000
> #define K 10000
> 
> double data[N];
> 
> int main()
> {
>     clock_t t = clock();
>     for (unsigned long n = 0; n < N; ++n)
>         for (unsigned long k = 0; k < K; ++k)
>             data[n] += data[n] * data[k];
> 
>     t = clock() - t;
>     printf("Time %.3f\n", (double)t / CLOCKS_PER_SEC);
> 
>     return 0;
> }
> 
> When I compile it using Cygwin's gcc, time shows CPU time (user time) as
> expected:
> 
> $ gcc -o test test.c -O3
> $ time ./test
> Time 1.890
> 
> real    0m2,043s
> user    0m1,890s
> sys     0m0,000s
> 
> However when code is compiled using MinGW's gcc, time reports 0.000 as a
> user time. Note that clock() function still provides valid values:
> 
> $ x86_64-w64-mingw32-gcc -o test test.c -O3
> $ time ./test
> Time 1.889
> 
> real    0m1,998s
> user    0m0,000s
> sys     0m0,015s
> 
> I have updated Cygwin to latest version today.
> $ uname -r
> 2.9.0(0.318/5/3)
> 
> gcc (GCC) 6.4.0
> x86_64-w64-mingw32-gcc (GCC) 6.4.0
> 
> I am using Win10 Pro now. As I recall, it worked when I was using it
> about year ago on Win7 Pro. So it is probably Win10 issue.
> 
> Is this a known bug, or should I log a new one? Do you know if there is
> any workaround?
> 
> Daniel
> 

I'd be surprised if a past or present cygwin could capture user or full
sys time from a .exe not linked against cygwin dll.  clock() relies on
library code which is part of the .exe.


-- 
Tim Prince

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