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| <title>Boost Basic Linear Algebra - Configuration Options</title> |
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| <h1><img src="../../../../boost.png" align="middle" alt="logo"/>Boost Basic Linear Algebra - Configuration Options</h1> |
| <div class="toc" id="toc"></div> |
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| |
| <h2>NDEBUG</h2> |
| |
| <p><strong>Make sure you define NDEBUG</strong> The only way uBLAS |
| knows you want a release configuration is to check if you have defined |
| NDEBUG. If you don't it assumes you want a debug configuration and |
| adds a lot of very useful runtime check. However these are very slow! |
| </p> |
| |
| |
| <h2>BOOST_UBLAS_MOVE_SEMANTICS</h2> |
| |
| <p class="credit">The patch and description was provided by Nasos Iliopoulos.</p> |
| |
| <p>An immediate effect of this option is the elimination of the need |
| for noalias in types <tt>vector<T></tt> and <tt>matrix<T></tt>, |
| when assigned to the same type. This option doesn't have an effect on |
| bounded and c types. Although it is rare, not all compilers support copy |
| elision (that allows for move semantics), so a test must be performed to |
| make sure that there is a benefit when it is enabled. A small |
| demonstration and test can be found in |
| <a href="../test/manual/test_move_semantics.cpp"><tt>test_move_semantics.cpp</tt></a></p> |
| |
| <p> |
| In the <a href="../test/manual/test_move_semantics.cpp">test |
| example</a> two tests are defined, one for vectors and one for |
| matrices. The aim of this example is to print the pointers of the |
| storage of each of the containers, before and after the assignment to |
| a temporary object. When move semantics are enabled, the |
| <tt>vector<T></tt> and <tt>matrix<T></tt> storage is moved |
| from the temporary and no copy is performed. |
| </p> |
| |
| <p> |
| If move semantics are supported by your compiler you will get an output like the following: |
| </p> |
| <pre class="screen"> |
| matrix<double> -------------------------------------------------------------------- |
| Temporary pointer r: 0x94790c0 |
| Pointer (must be equal to temp. pointer if move semantics are enabled) : 0x94790c0 |
| </pre> |
| |
| <p>Notes:</p> |
| <ul> |
| <li>It should be no surprise to see matrices and vectors been passed |
| by VALUE, the compiler takes care and either moves (if the underlying |
| code does not modify the object), or copies (if the underlying code |
| modifies the object). |
| </li> |
| <li>There might be some space for some improvements (like clearing the |
| data, before swaping) |
| </li> |
| <li>Move semantics don't eliminate temporaries. They rather move their |
| storage around so no copies are performed. |
| </li> |
| <li>MSVC does no implement Named Return Value Optimization in debug |
| mode. So if you build in debug with this compiler you might get <a |
| href="https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=483229" |
| target="_blank">different behaviour</a> than a release build. |
| </li> |
| <li>Enabling move semantics is done via #define BOOST_UBLAS_MOVE_SEMANTICS. |
| </li> |
| <li>There is plenty of room for optimizations when c++0x standard is |
| out, taking advantage of rvalue references. (I have a sweet vector |
| implementation using that). |
| </li> |
| <li>If you enable move semantics and your compiler does not support |
| them, the operation will just be as passing by const reference. |
| </li> |
| </ul> |
| |
| <p>Interesting links</p> |
| <ul> |
| <li> <a href="http://cpp-next.com/archive/2009/08/want-speed-pass-by-value/" target="_blank">Want Speed? Pass by Value.</a> |
| </li> |
| <li> <a href="http://blogs.msdn.com/vcblog/archive/2009/02/03/rvalue-references-c-0x-features-in-vc10-part-2.aspx" target="_blank">Rvalue References: C++0x Features in VC10, Part 2</a> |
| </li> |
| <li> <a href="http://cpp-next.com/archive/2009/09/move-it-with-rvalue-references/" target="_blank">Move It With Rvalue References</a> |
| </li> |
| </ul> |
| |
| <h2>BOOST_UBLAS_CHECK_ENABLE</h2> |
| |
| <p>When BOOST_UBLAS_CHECK_ENABLE is defined then all index and |
| parameter checks are enabled. This is enabled in debug mode and |
| disabled in release mode. |
| </p> |
| |
| <h2>BOOST_UBLAS_TYPE_CHECK</h2> |
| |
| <p>When BOOST_UBLAS_TYPE_CHECK is enabled then all possibly expensive |
| structure checks are enabled. If this is not desireable then use |
| <tt>#define BOOST_UBLAS_TYPE_CHECK 0</tt> before including any uBLAS |
| header. The define BOOST_UBLAS_TYPE_CHECK_EPSILON can be used to |
| control the acceptable tolerance, see |
| <tt>detail/matrix_assign.hpp</tt> for implementation details of this |
| check. |
| </p> |
| |
| <h2>BOOST_UBLAS_USE_LONG_DOUBLE</h2> |
| |
| <p>Enable uBLAS expressions that involve containers of 'long double'</p> |
| |
| <h2>BOOST_UBLAS_USE_INTERVAL</h2> |
| |
| <p>Enable uBLAS expressions that involve containers of 'boost::numeric::interval' types</p> |
| |
| <h2>Configuring uBLAS with Macros</h2> |
| |
| <p>Many macro's appear in ublas/config.hpp and elsewhere. Hopefully in the future some of these will disappear! |
| They fall into 4 groups: |
| </p> |
| <ul> |
| <li> Automatically set by 'boost/numeric/ublas/config.hpp' based on |
| NDEBUG. Makes the distinction between debug (safe) and release (fast) |
| mode. Similar to STLport |
| <ul> |
| <li> <i>Release</i> mode (NDEBUG defined) |
| <ul> |
| <li> BOOST_UBLAS_INLINE <i>Compiler dependant definition to control |
| function inlining.</i> </li><li> BOOST_UBLAS_USE_FAST_SAME </li></ul> |
| </li><li> <i>Debug</i> mode |
| <ul> |
| <li> BOOST_UBLAS_CHECK_ENABLE <i>Enable checking of indexs, iterators |
| and parameters. Prevents out of bound access etc.</i> </li><li> |
| BOOST_UBLAS_TYPE_CHECK <i>Enable additional checks for the results of |
| expressions using non dense types. Picks up runtime error such as the |
| assignment of a numerically non-symmetric matrix to |
| symmertic_matrix. Use <tt>#define BOOST_UBLAS_TYPE_CHECK 0</tt> to |
| disable expensive numeric type checks.</i> (Note: "structure check" |
| would be a much better name.) </li><li> |
| BOOST_UBLAS_TYPE_CHECK_EPSILON <i>default: sqrt(epsilon), controls how |
| large the difference between the expected result and the computed |
| result may become. Increase this value if you are going to use near |
| singular or badly scaled matrices. Please, refer to |
| <tt>detail/matrix_assign.hpp</tt> for implementation of these type |
| checks.</i> </li></ul> </li></ul> |
| </li> |
| <li> Automatically set by 'boost/numeric/ublas/config.hpp' based on |
| compiler and boost/config.hpp macro's. Augments the compiler |
| deficiency workarounds already supplied by boost/config.hpp |
| <ul> |
| <li> BOOST_UBLAS_NO_NESTED_CLASS_RELATION <i>A particularly nasty |
| problem with VC7.1 Requires that uBLAS and the user use begin(it) |
| rather then it.begin()</i> </li><li> BOOST_UBLAS_NO_SMART_PROXIES |
| <i>Disable the automatic propagation of 'constantness' to |
| proxies. Smart proxies automatically determine if the underling |
| container they reference is constant or not. They adjust there |
| definition of iterators and container access to reflect this |
| constantness.</i> </li></ul> |
| </li> |
| <li> For use by uBLAS authors to test implementation methods. Preset |
| in config.hpp |
| <ul> |
| <li> BOOST_UBLAS_USE_INVARIANT_HOISTING </li><li> |
| BOOST_UBLAS_USE_INDEXING </li><li> BOOST_UBLAS_USE_INDEXED_ITERATOR |
| </li><li> BOOST_UBLAS_NON_CONFORMANT_PROXIES <i>Gappy containers may |
| be non-conformant, that is contain elements at different |
| indices. Assigning between proxies (vector ranges for example) of |
| these containers is difficult as the LHS may need insert new |
| elements. This is slow.</i> </li><li> BOOST_UBLAS_USE_DUFF_DEVICE |
| <i>Near useless on all platforms (see GCC's -funroll-loops)</i> |
| |
| </li></ul> |
| </li> |
| <li> User options. Can be predefined by user before including any |
| uBLAS headers. They may also be automatically defined for some |
| compilers to work around compile bugs. |
| <ul> |
| <li> BOOST_UBLAS_USE_LONG_DOUBLE <i>Enable uBLAS expressions that |
| involve containers of 'long double'</i> </li><li> |
| BOOST_UBLAS_USE_INTERVAL <i>Enable uBLAS expressions that involve |
| containers of 'boost::numeric::interval' types</i> </li><li> |
| BOOST_UBLAS_SIMPLE_ET_DEBUG <i>In order to simplify debugging is is |
| possible to simplify expression templateso they are restricted to a |
| single operation</i> |
| |
| </li><li> BOOST_UBLAS_ENABLE_PROXY_SHORTCUTS <i> enable automatic |
| conversion from proxy class to matrix expression </i> </li><li> |
| BOOST_UBLAS_NO_ELEMENT_PROXIES <i>Disables the use of element proxies |
| for gappy types.</i> </li><li> <i>The Gappy types (sparse, coordinate, |
| compressed) store non-zero elements in their own containers. When new |
| non-zero elements are assigned they must rearrange these |
| containers. This invalidates references, iterators or pointers to |
| these elements. This can happen at some surprising times such as the |
| expression "a [1] = a [0] = 1;". Element proxies guarantee all such |
| expressions will work as expected. However they bring their own |
| restrictions and efficiency problems. For example as of Boost 1.30.0 |
| they prevent the assignment of elements between different types.</i> |
| </li> |
| <li> BOOST_UBLAS_REFERENCE_CONST_MEMBER <i>Enable to allow refernces |
| to be returned to fixed (zero or one) elements of triangular or banded |
| matrices</i> |
| |
| </li><li> BOOST_UBLAS_NO_EXCEPTIONS <i>Disable the use exceptions of |
| uBLAS internal checks and error conditions. BOOST_NO_EXCEPTIONS has |
| same effect.</i> |
| </li> |
| <li> BOOST_UBLAS_SINGULAR_CHECK <i>Check the for singularity in triangular solve() functions</i></li> |
| </ul> |
| </li> |
| </ul> |
| |
| <hr /> |
| <div id="copyright"> |
| <p>Copyright (©) 2000-2009 Joerg Walter, Mathias Koch, Gunter Winkler<br /> |
| Use, modification and distribution are subject to the Boost Software License, Version 1.0. |
| (See accompanying file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt"> |
| http://www.boost.org/LICENSE_1_0.txt |
| </a>). |
| </p> |
| </div> |
| <div id="revision"> |
| <p> |
| <!-- Created: Wed Sep 16 21:19:20 CEST 2009 --> |
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| Last modified: Wed Sep 16 23:16:45 CEST 2009 |
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