X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=docs%2Fusers_guide%2Fparallel.xml;h=b8e73166e4e4e500ed898a53cd660792f4af549a;hb=HEAD;hp=37cafd2d764e2aad43ab3fa636099383f18a9ce8;hpb=816b587f0057113ce9667f1f643d828d7abe2079;p=ghc-hetmet.git diff --git a/docs/users_guide/parallel.xml b/docs/users_guide/parallel.xml index 37cafd2..b8e7316 100644 --- a/docs/users_guide/parallel.xml +++ b/docs/users_guide/parallel.xml @@ -4,7 +4,7 @@ parallelism - GHC implements some major extensions to Haskell to support + GHC implements some major extensions to Haskell to support concurrent and parallel programming. Let us first establish terminology: Parallelism means running @@ -12,16 +12,16 @@ performance. Ideally, this should be done invisibly, and with no semantic changes. - Concurrency means implementing + Concurrency means implementing a program by using multiple I/O-performing threads. While a - concurrent Haskell program can run on a + concurrent Haskell program can run on a parallel machine, the primary goal of using concurrency is not to gain performance, but rather because that is the simplest and most direct way to write the program. Since the threads perform I/O, the semantics of the program is necessarily non-deterministic. - GHC supports both concurrency and parallelism. + GHC supports both concurrency and parallelism. @@ -38,7 +38,7 @@ To the programmer, Concurrent Haskell introduces no new language constructs; rather, it appears simply as a library, + url="&libraryBaseLocation;/Control-Concurrent.html"> Control.Concurrent. The functions exported by this library include: @@ -55,15 +55,15 @@ the FFI with concurrency. Software Transactional Memory GHC now supports a new way to coordinate the activities of Concurrent - Haskell threads, called Software Transactional Memory (STM). The + Haskell threads, called Software Transactional Memory (STM). The STM papers are an excellent introduction to what STM is, and how to use it. - The main library you need to use STM is - Control.Concurrent.STM. The main features supported are these: + The main library you need to use is the + stm library. The main features supported are these: Atomic blocks. Transactional variables. @@ -78,7 +78,7 @@ All these features are described in the papers mentioned earlier. Parallel Haskell GHC includes support for running Haskell programs in parallel - on symmetric, shared-memory multi-processor + on symmetric, shared-memory multi-processor (SMP)SMP. By default GHC runs your program on one processor; if you want it to run in parallel you must link your program @@ -109,8 +109,8 @@ All these features are described in the papers mentioned earlier. One way to do so is forking threads using Concurrent Haskell (), but the simplest mechanism for extracting parallelism from pure code is to use the par combinator, which is closely related to (and often used - with) seq. Both of these are available from Control.Parallel: + with) seq. Both of these are available from the parallel library: infixr 0 `par` @@ -177,8 +177,9 @@ nfib n | n <= 1 = 1 statistics; see . More sophisticated combinators for expressing parallelism are - available from the Control.Parallel.Strategies module. + available from the Control.Parallel.Strategies + module in the parallel package. This module builds functionality around par, expressing more elaborate patterns of parallel computation, such as parallel map. @@ -196,7 +197,6 @@ nfib n | n <= 1 = 1