is D so slow?

[Unknown W. Brackets]

What about switches?  Your program uses arrays; if you have array bounds 
checks enabled, that could easily account for the difference.

One way to see is dump the assembly (I think there's a utility called 
dumpobj included with dmd) and compare.  Obviously, it's doing something 
differently - there's nothing instrinsically "slower" about the language 
for sure.

Also - keep in mind that gdc doesn't take advantage of all the 
optimizations that gcc is able to provide, at least at this time.  A 
couple of bytes can go a long long way if not optimized right.

-[Unknown]


baleog wrote:
> Unknown W. Brackets Wrote:
>> What compilers are you comparing?  
> 
> gcc-4.0 with last releases of the gdc and dmd-2 
> 
>> They have different optimization
> 
> but gdc uses gcc backend and the test programs (C and D) differs by the couple of bytes..
> i used std.gc.disable() too - nothing changed
> 
>> backends.  It could be that the C compiler or compiler flags you are 
>> using simply perform better than the comparable D compiler and flags.
>>
>> -[Unknown]
>>
>>
>> baleog wrote:
>>> Hello
>>> I wrote 2 almost identical test programs(matrix multiplication). One on C and another on D. And D prorgram was 15 times slower! 
>>> Was it my mistake or not?
>>> Thank you
>>>
>>> p.s. code:
>>> void test (int n) {  
>>>   float[] xs = new float[n*n];
>>>   float[] ys = new float[n*n];
>>>   for(int i = n-1; i>=0; --i) {
>>>     xs[i] = 1.0;
>>>   }
>>>  for(int i = n-1; i>=0; --i) {
>>>     ys[i] = 2.0;
>>>   }
>>>   float[] zs = new float[n*n];
>>>   for (int i=0; i<n; ++i) {
>>>     for (int j=0; j<n; ++j) {
>>>       float s = 0.0;
>>>       for (int k=0; k<n; ++k) {
>>>         s = s + (xs[k + (i*n)] * ys[j + (k*n)]);
>>>       }
>>>       zs[j+ (i*n)] =  s;
>>>     }
>>>   }
>>>   delete xs;
>>>   delete ys;
>>>   delete zs;
>>> }
>>>
>