gc vs explicit

[zz]

Walter Bright wrote:
> zz wrote:
> 
>>  From my point of view these tests are not really nessesary on my side 
>> since I still continue using D and I belive that someday the memory 
>> stuff will be optimized.
> 
> 
> One thing that is happening is that the C++ code allocates memory, it 
> never frees it. The same with the D code.

Not until it's out of scope (in this case main).

> What happens with a garbage collector is it gets new chunks of memory 
> from the operating system as it needs it. But before it does, it runs a 
> collection cycle.

Would something like dlmalloc by Doug Lea make a difference in D, 
someone suggested trying it out so I tested it using DMC on some C code 
and there was a big difference the two compiled versions (Numbers are 
below and I was supprised).

> So in the D version, it will be running probably several collection 
> cycles (accomplishing nothing), while the C++ version does not. This 
> will make the gc version slower.
> 
> To get better numbers, one can add calls to gc.disable() and gc.enable() 
> to tell the gc that there is no point to running a collection cycle for 
> this section of code.

The above is something that, i'll not do (In DMC i can get better 
numbers by just changing my allocator how can I go about it in D).

Zz

-----------------------------------------------
- Default memory allocator
dmc -o+all test.c
Capacity C: 1048576  Count: 1000000

ContextSwitches - 19954
First level fills = 0
Second level fills = 0

ETime(   0:00:06.562 ) UTime(   0:00:06.015 ) KTime(   0:00:00.375 )
ITime(   0:00:03.828 )


-----------------------------------------------
dmc -DREPLACE_SYSTEM_ALLOCATOR -o+all test.c
Capacity C: 1048576  Count: 1000000

ContextSwitches - 3092
First level fills = 0
Second level fills = 0

ETime(   0:00:01.250 ) UTime(   0:00:00.968 ) KTime(   0:00:00.250 )
ITime(   0:00:00.796 )

Note: I used dlmalloc Version pre-2.8.4 Wed Aug  2 14:13:56 2006 which 
comes with nedmalloc.
The current version is 2.8.3 and ptmalloc3 comes with an earlier version 
of the one used above.