a5b14d74b7
* typos * reorder and reword raco exe flags for CS/BC Suggestsions from @sorawee, thanks! * make two suggested edits, retract one
47 lines
2.1 KiB
Racket
47 lines
2.1 KiB
Racket
#lang scribble/doc
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@(require "mz.rkt")
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@title[#:tag "implementations" #:style 'quiet]{Implementations}
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The definition of Racket aims for determinism and independence from
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its implementation. Nevertheless, some details inevitably vary with
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the implementation. Racket currently has two main implementations:
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@itemlist[
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@item{The @deftech{CS} implementation is the default implementation
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as of Racket version 8.0. This variant is called ``CS'' because
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it uses Chez Scheme as its core compiler and runtime system.
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The CS implementation typically provides the best performance
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for Racket programs. Compiled Racket CS code in a
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@filepath{.zo} file normally contains machine code that is
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specific to an operating system and architecture.}
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@item{The @deftech{BC} implementation was the default implementation
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up until version 7.9. The ``BC'' label stands for ``before
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Chez'' or ``bytecode.''
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Compiled Racket BC code in a @filepath{.zo} file normally
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contains platform-independent bytecode that is further compiled
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to machine code ``just in time'' as the code is loaded.
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Racket BC has two variants: @deftech{3m} and @deftech{CGC}.
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The difference is the @tech{garbage collection} implementation,
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where 3m uses a garbage collector that moves objects in memory
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(an effect that is visible to foreign libraries, for example)
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and keeps precise track of allocated objects, while CGC uses a
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``conservative'' collector that requires less cooperation from
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an embedding foreign environment. The 3m subvariant tends to
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perform much better than CGC, and it became the default
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variant in version 370 (which would be v3.7 in the current
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versioning convention).}
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]
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Most Racket programs run the same in all implementation variants, but some Racket
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features are available only on some implementation variants, and the
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interaction of Racket and foreign functions is significantly different
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across the variants. Use @racket[system-type] to get information about
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the current running implementation.
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