Slow D
Here I have collected few benchmarks where the D language, or the DMD compiler, or the Phobos std lib don't shine in their performance. Two of the following performance problems (see 'gc1' and 'sort' benchmarks) have already a solution.

http://www.fantascienza.net/leonardo/js/slow_d.zip

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Compilers/interpreters used:
Digital Mars D Compiler v1.028

gcc version 4.2.1-dw2 (mingw32-2)

Python 2.5.2 (r252:60911, Feb 21 2008, 13:11:45) [MSC v.1310 32 bit (Intel)] on win32

Psyco V.1.5.2 (JIT for Python)

javac 1.6.0_03, Java version "1.6.0_03"


All timings are "warm", best of 3, in seconds.
CPU used is a Pentium3 500 MHz, 256 MB RAM, with Win.


Compilation flags used (when not specified otherwise):
gcc: -O3 -s
dmd: -O -release -inline
Python: no flags.

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BENCHMARKS:

recursive, n = 38:
  C: 3.89 s (with __builtin_expect)
  C: 3.99 s
  D: 4.95 s


hash, n = 500_000:
  D:     7.07 s (7.15 s with GC patched)
  D:     5.89 s (GC disabled)
  Psyco: 4.23 s

(Note that Python+Psyco has much bigger overhead compared to D in any instruction, simple loops too).

wordcount, on a txt file of 13_312_768 bytes:
  C: 0.73 s
  D: 5.77 s


gc1, with 6.3 MB of text:
        loading   splitting   total
         time        time     time
  D:       1.87 s     3.58 s   13.76 s
  Python:  0.28 s     1.98 s    3.52 s
  Python:  0.1 s      2.0 s     3.38 s (load with 'rb', same result)
With a Patch to the D GC, plus disabling the GC:
  D:       0.08 s     0.72 s    1.36 s (GC patched + GC disabled after load)


gc2, n=1_000, m=10_000:
               seconds  MB
  DMD class:   18.95    1.7
  GDC class:   17.91    1.8
  DMD struct:  11.77    1.7
  GDC struct:  12.31    1.8
  Python:      37.10    3.1
  Psyco:       15.68    3.5
  Java:         2.19    7.3


gc3 (binarytrees), n = 15:
  Java:   9.12 s
  D:     35.01 s


sort, const n = 1_000_000:
  Random distribution:
    sort: 2.934
    fastSort: 0.881
  Already sorted arrays:
    sort: 1.723
    fastSort: 0.41
 Inverted order arrays:
    sort: 1.853
    fastSort: 0.651

(For a better and more complete version of fastSort see my D libs:
www.fantascienza.net/leonardo/so/libs_d.zip ).