Plan for the December 2010 Release

To be released components

• GHC 7.0.2
• DPH packages
• Repa packages

(No release of vector should be necessary, as 0.7.0.1 should work fine.)

Before the release we must achieve the following

Documentation:

• Haddock documentation of Data.Array.Parallel [???]
• HowTo and examples on HaWiki  http://haskell.org/haskellwiki/GHC/Data_Parallel_Haskell [MANUEL]
• Replace -XPArr by -XParallelArrays in the Users Guide, also add -fvectorise

API adaptation: APIs of vector, Repa, and Accelerate should be unified as far as possible

• Repa's current 'replicate' should be renamed and a new 'replicate' that turns a scalar into an array should be introduced [???]
• Check similarity of singleton/unit between all three libraries [???]

Changes:

• -fdph-par should be the default (and sensible error message if the dph package is not available) (done, but need to still sort out a build problem) [MANUEL]
• -Odph should be equivalent to '-O2 -fsimplifier-phases=3 -fsimplifier-iterations=20' (done, not pushed yet) [MANUEL]
• Move GHC.PArr into the DPH libs. (Needed for Haddock.) [MANUEL]
• Find out if we still need the NoSpecConstr annotation and remove it if not [ROMAN]

Bug fixes:

• Vectoriser needs to be adapted to Simon's recursive superclasses patch [ROMAN]
• The combination '-fvectorise -O0' should work [ROMAN]
• Trying to vectorise the DotP example from the tutorial on the Haskell Wiki, -fdph-seq fails with (-fdph-par works fine)

  *** Vectorisation error ***
      Tycon not vectorised:  Data.Array.Parallel.Lifted.PArray.PArray
  

• LLVM back end not working with DPH (held up due to LLVM backend problems in the HEAD) [BEN]
• Repa edge-detection is deadlocking with more than 2 threads [DONE]
• Fix the BH seg fault in DPH. Roman has found the problem [DONE]

Performance goals:

• Vector works fast, sequentially, compared to C, Haskell mutable-array version [FINE]
  • Benchmarks: NoSlow, vector versions of Repa benchmarks
• Repa works fast in parallel
  • MMult [OK, but about 20% slower than in 6.13; try with LLVM and w/o bounds checks] [BEN]
  • Laplace (blocked on LLVM backend problems) [SLOW & DOESN'T SCALE] [BEN]
  • Blur [OK]
  • EdgeDetect [OK]
  • FFT [OK]
• Statically-nested DPH programs should work fast, in parallel
  • SumSquares [FINE]
  • Dot product [FINE]
  • Evens [OK (but more than 3 times slower than C; any improvement since #4830 was fixed?)]
    • rl reckons this is due to GHC compiling modulo of powers of two inefficiently; c.f., #3065 (in packByTags)
  • SMVM (blocked on optimisation of lifted indexing) [BROKEN] [BEN & ROMAN]
• Dynamically-nested DPH programs without user-defined datatypes should run correctly, but not necessarily fast
  • Quicksort [BROKEN (SpecConstr) & SLOW] [SIMON & BEN]
  • Quickhull [OK, but has a SpecConstr problem that we want to fix] [ROMAN]
    • Probably affected by the same optimisation issue with the compilation of modulo operations as Evens
    • #4830: this fix wasn't sufficient, still doesn't optimise properly
• Dynamically-nested DPH programs with user-defined datatypes should run correctly, but not necessarily fast
  • Words [BROKEN (SpecConstr when using -dph-seq)] [ROMAN & SIMON]
    • #4831
  • BarnesHut [OK]

Legend

[FINE]

Works well

[OK]

Fine for the release, but could be better

[SLOW]

Not usable

Tags in bold require attention before the release.

More benchmarks details at DataParallel/BenchmarkStatus