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<title>Diderot project</title>
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<h2 align="center">The Diderot Project</h2>
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<h3>About</h3>
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<p>
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The Diderot project is an effort to design and implement a <i>Parallel
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Domain-specific Language</i> (PDSL) for image analysis and visualization.
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We are particularly interested in a class of algorithms that are programmed
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in terms of <em>continuous</em> scalar, vector, and tensor fields that
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are reconstructed from the image data.
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Our goals are to provide a high-level mathematical programming model for
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these algorithms, while also providing high-performance implementations
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on a variety of parallel hardware platforms.
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</p>
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<h3>Language overview</h3>
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<p>
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The following is an overview of our current preliminary design for Diderot.
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We are building a compiler for this design and expect that the design will
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evolve as we get experience with the implementation.
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Also, the design is conservative, in that it does not provide all of the features that
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we plan to provide (<i>e.g.</i>, actor-actor interactions).
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</p>
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<h4>Types</h4>
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The main type of computational value in Diderot is a <em>tensor</em>, which includes
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reals (0-order tensors), vectors, and matrices.
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In addition, Diderot provides booleans, integers, and strings.
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Diderot also has three <em>abstract</em> types:
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</p>
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<dl>
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<dt>images</dt>
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<dd>are used to represent the data being analyzed, as well as other array data, such as transfer
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functions.
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</dd>
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<dt>kernels</dt>
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<dd>are separable convolution kernels</dd>
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<dt>fields</dt>
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<dd>are an abstraction of functions from 1D, 2D, or 3D space to some tensor type.
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A field is defined by convolving an image with a kernel.
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</dd>
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</dl>
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<h4>Program structure</h4>
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<p>A Diderot program is organized into three logical sections:</p>
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<ol>
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<li>Global declarations define global values, such as fields, as well as the inputs to the program.</li>
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<li>Actor definitions define the computational agents that implement the program</li>
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<li>Initialization defines the initial set of actors and their structure</li>
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</ol>
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<h4>Actors</h4>
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<p>
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An <em>actor</em> represents a mostly autonomous computation with local state, which includes
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their <em>position</em> in world space.
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An actor definition consists of declared state variables and methods.
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All actors must have an <em>update</em> method and may optionally have a <em>stabilize</em>
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method.
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</p>
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<h4>Execution model</h4>
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<p>The Diderot execution model is <em>bulk synchronous</em>.
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At each iteration, the update methods of all active actors are invoked, resulting in a new
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configuration.
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</p>
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<h3>People</h3>
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<ul>
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<li><a href="http://cs.uchicago.edu/~glk/">Gordon Kindlmann</a></li>
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<li><a href="http://cs.uchicago.edu/~jhr/">John Reppy</a></li>
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<li><a href="http://www.cs.uchicago.edu/people/lamonts">Lamont Samuels</a></li>
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</ul>
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<h3>Status</h3>
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<p>
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We have a prototype language design that can handle simple examples, such as volume
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rendering, and we are working on a baseline compiler for the design.
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This compiler will generate CUDA or OpenCL code for running on GPUs.
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</p>
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<hr />
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Last modified: October 4, 2010.
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