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 0.7.01 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]

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 [MANUEL]
• -fvectorise should imply -Odph (if omitted, we get fatal errors) [MANUEL]
  • rl notes, "We shouldn't! -fvectorise -O0 should work, I'll take a look. I should change -Odph to reflect what we currently need, though. Basically, it should be equivalent ot -O2 -fsimplifier-phases=3 -fsimplifier-iterations=20."
• 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:

• Repa edge-detection is deadlocking with more than 2 threads [DONE]
• Fix the BH seg fault in DPH. Roman has found the problem [DONE]
• LLVM back end not working with DPH [BEN]

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 [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)]'
    • rl reckons this is due to GHC compiling modulo of powers of two inefficiently; c.f., #3065 (in packByTags)
  • SMVM [SLOW (lack of fusion)] [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
• Dynamically-nested DPH programs with user-defined datatypes should run correctly, but not necessarily fast
  • Words [BROKEN (SpecConstr)] [SIMON]
  • 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