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- Organize the documentation into "chapters". - Each chapter include many documentation pages, reference pages organized as modules, and a quick reference page. - The "Chapters" tree is created using the defgroup/ingroup mechanism, even for the documentation pages (i.e., .dox files for which I added an \eigenManualPage macro that we can switch between \page or \defgroup ). - Add a "General topics" entry for all pages that do not fit well in the previous "chapters". - The highlevel struture is managed by a new eigendoxy_layout.xml file. - remove the "index" and quite useless pages (namespace list, class hierarchy, member list, file list, etc.) - add the javascript search-engine. - add the "treeview" panel. - remove \tableofcontents (replace them by a custom \eigenAutoToc macro to be able to easily re-enable if needed). - add javascript to automatically generate a TOC from the h1/h2 tags of the current page, and put the TOC in the left side panel. - overload various javascript function generated by doxygen to: - remove the root of the treeview - remove links to section/subsection from the treeview - automatically expand the "Chapters" section - automatically expand the current section - adjust the height of the treeview to take into account the TOC - always use the default .css file, eigendoxy.css now only includes our modifications - use Doxyfile to specify our logo - remove cross references to unsupported modules (temporarily)
39 lines
1.6 KiB
Plaintext
39 lines
1.6 KiB
Plaintext
namespace Eigen {
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/** \eigenManualPage TopicFixedSizeVectorizable Fixed-size vectorizable Eigen objects
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The goal of this page is to explain what we mean by "fixed-size vectorizable".
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\section summary Executive Summary
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An Eigen object is called "fixed-size vectorizable" if it has fixed size and that size is a multiple of 16 bytes.
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Examples include:
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\li Eigen::Vector2d
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\li Eigen::Vector4d
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\li Eigen::Vector4f
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\li Eigen::Matrix2d
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\li Eigen::Matrix2f
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\li Eigen::Matrix4d
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\li Eigen::Matrix4f
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\li Eigen::Affine3d
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\li Eigen::Affine3f
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\li Eigen::Quaterniond
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\li Eigen::Quaternionf
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\section explanation Explanation
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First, "fixed-size" should be clear: an Eigen object has fixed size if its number of rows and its number of columns are fixed at compile-time. So for example Matrix3f has fixed size, but MatrixXf doesn't (the opposite of fixed-size is dynamic-size).
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The array of coefficients of a fixed-size Eigen object is a plain "static array", it is not dynamically allocated. For example, the data behind a Matrix4f is just a "float array[16]".
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Fixed-size objects are typically very small, which means that we want to handle them with zero runtime overhead -- both in terms of memory usage and of speed.
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Now, vectorization (both SSE and AltiVec) works with 128-bit packets. Moreover, for performance reasons, these packets need to be have 128-bit alignment.
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So it turns out that the only way that fixed-size Eigen objects can be vectorized, is if their size is a multiple of 128 bits, or 16 bytes. Eigen will then request 16-byte alignment for these objects, and henceforth rely on these objects being aligned so no runtime check for alignment is performed.
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*/
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}
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