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126 lines
3.6 KiB
Plaintext
126 lines
3.6 KiB
Plaintext
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= CompTree
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== Summary
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A simple framework for automatic parallelism.
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== Synopsis
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require 'comp_tree'
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CompTree.build do |driver|
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# Define a function named 'area' taking these two arguments.
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driver.define(:area, :width, :height) { |width, height|
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width*height
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}
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# Define a function 'width' which takes a 'border' argument.
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driver.define(:width, :border) { |border|
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7 + border
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}
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# Ditto for 'height'.
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driver.define(:height, :border) { |border|
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5 + border
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}
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# Define a constant function 'border'.
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driver.define(:border) {
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2
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}
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# Compute the area using four parallel threads.
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puts driver.compute(:area, 4)
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# => 63
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# We've done this computation.
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puts((7 + 2)*(5 + 2))
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# => 63
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end
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== Install
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% gem install comp_tree
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Or for the (non-gem) .tgz package,
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% ruby install.rb [--uninstall]
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== Description
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CompTree is a parallel computation tree structure based upon concepts
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from pure functional programming.
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The user should have a basic understanding of functional programming
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(see for example http://en.wikipedia.org/wiki/Functional_programming)
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and the meaning of <em>side effects</em>.
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Every function you define must explicitly depend on the data it uses.
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#
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# BAD example: depending on state -- offset not listed as a parameter
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#
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driver.define(:area, :width, :height) { |width, height|
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width*height - offset
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}
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Unless <em>offset</em> is really a constant, the result of
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<tt>driver.compute(:area, n)</tt> is not well-defined for _n_ > 1.
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Just as depending on some changeable state is bad, it is likewise bad
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to affect a state (to produce a <em>side effect</em>).
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#
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# BAD example: affecting state
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#
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driver.define(:area, :width, :height) { |width, height|
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accumulator.add "more data"
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width*height
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}
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Given a tree where nodes are modifying _accumulator_, the end state of
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_accumulator_ is not well-defined, even if _accumulator_ is a
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thread-safe object.
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Note however it is OK affect a state as long as <em>no other function
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depends on that state</em>. This is the principle under which
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CompTree parallelizes Rake tasks (http://drake.rubyforge.org).
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== Links
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* Documentation: http://comptree.rubyforge.org
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* Download: http://rubyforge.org/frs/?group_id=6917
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* Rubyforge home: http://rubyforge.org/projects/comptree
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* Repository: http://github.com/quix/comp_tree
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== Author
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* James M. Lawrence <quixoticsycophant@gmail.com>
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== License
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Copyright (c) 2008, 2009 James M. Lawrence. All rights reserved.
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Permission is hereby granted, free of charge, to any person
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obtaining a copy of this software and associated documentation files
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(the "Software"), to deal in the Software without restriction,
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including without limitation the rights to use, copy, modify, merge,
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publish, distribute, sublicense, and/or sell copies of the Software,
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and to permit persons to whom the Software is furnished to do so,
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subject to the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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