Garbage collection in D

[Rainer Deyke]

Sam Hu wrote:
> What does this result mean?Does it mean D is slower than Java and C++
> is also slower than Java?Or that's true just under  certain
> circumstance? I am really confused and really appreicate if any
> further explanation.

These are the timings for using dynamic memory allocation:
>>   D 1:  40.20 DMD
>>   D 2:  21.83 DMD
>>   C++:  18.06
>>   Java:  1.38 V.1.6.0_14

Java is the fastest by a large margin because it has the benefit of a
moving garbage collector.  This means allocation is a simple pointer
bump and deallocation is completely free.  The slow aspects of this
garbage collector (detection and preservation) aren't really tested by
this benchmark.

These are the timings without dynamic memory allocation:
>>   D 1:   8.47 DMD [+ scope]
>>   D 2:   7.41 DMD + scope
>>   Java:  0.28 V.1.6.0_14, -server -XX:+DoEscapeAnalysis

D's performance is unexpectedly bad, so much that I expect that it might
be using dynamic memory allocation anyway despite the 'scope' keyword.
Java is clever in that it eliminates unnecessary dynamic memory
allocations automatically.  C++ is notable absent, but I fully expect it
to outperform Java by a significant margin.


-- 
Rainer Deyke - rainerd at eldwood.com