Hi, In my tests, FPC 2.4.4 has much slower CompareMem than FPC 2.4.2, at least for some cases:
# with fpc 2.4.4 $ time ./compare_mem_test 100000000 real 0m7.795s user 0m7.764s sys 0m0.008s # with fpc 2.4.2 $ time ./compare_mem_test 100000000 real 0m1.218s user 0m1.216s sys 0m0.000s This uses CompareMem to compare vectors 3 x Single (12 bytes). As you can see, FPC 2.4.2 is > 6 times faster, so it's a noticeable slowdown (especially if this is a bottleneck of your algorithm :). This is on Linux, i386 (32 bit). I'm attaching the sample compare_mem_test.lpr, just compile by "fpc compare_mem_test.lpr". I did some tests. In FPC 2.4.4 CompareMem equals to CompareByte. I tried using CompareWord, which is ~2 times faster, and CompareDWord, which is even better, but still --- even the best (CompareDWord) on FPC 2.4.4 is ~3 times slower than CompareMem on FPC 2.4.2. Funny thing is, the fastest approach turned out to be the simplest one: compare by "(V1[0] = V2[0]) and (V1[1] = V2[1]) and (V1[2] = V2[2])". This is *much* faster than every other approach. (And yes, I tested that it wasn't optimized out :) Any thoughts? Maybe something can be improved? 1. Why CompareMem got slower in FPC 2.4.4? Maybe something can be fixed? 2. The simple comparison "(V1[0] = V2[0]) and..." is much faster than any CompareXxx. Any chance of improving it? In this case, size is known at compile time, so maybe CompareXxx could be "magic" and (for reasonably small sizes) the compiler could just generate a proper code to compare them just like "=" operator? Just an idea of course, I don't know how easy it would be to actually implement. Michalis _______________________________________________ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
