Rainer Deyke: >The slow aspects of this garbage collector (detection and preservation) aren't >really tested by this benchmark.<
In practice most times real-world Java programs show a good enough performance even taking in account detection and preservation too. >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 It's not exactly the same, because in that Java code I have used a program-wide optimization flag (that I guess will become default), while in D I have had to add a "scope" everywhere, and I think adding "scope" is less safe than letting the compiler perform an escape analysis. So I am tempted to put the 0.28 seconds result among the dynamic allocation timings, even if technically it is not, because for the programmer the program "feels" and looks and acts like a dynamic allocation, it's just faster :-) In the end what counts is how well the programs runs after the compiler has done its work. >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.< I think Java here is doing a bit more than just removing the dynamic allocation. I don't think D (compiled with LDC) is doing doing any allocation here. I'll ask to the LDC IRC channel. I'll also take a look at the asm generated by the JavaVM (it's not handy to find the asm generated by the JVM, you need to install a debug version of it... how stupid). ------------------------- Sam Hu: >I am sorry to hear that,really,really sorry.< Wait, things may not be that bad. And even if they are bad, the developers of the LDC compiler may find ways to improve the situation. ------------------------- Robert Fraser: >It suggests that for dynamic allocation of many small objects via "new", Java >is an order of magnitude faster than C++, which in turn is slightly faster >than D.< Yes, for such tiny benchmarks I have seen several times 10-12 higher allocation performance in Java compared to D1-DMD. But real programs don't use all their time allocating and freeing memory... Bye, bearophile
