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12<title>Boost Basic Linear Algebra - Configuration Options</title>
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15<h1><img src="../../../../boost.png" align="middle" alt="logo"/>Boost Basic Linear Algebra - Configuration Options</h1>
16<div class="toc" id="toc"></div>
17
18<div class="navigation">
19<a href="index.html">back to uBLAS home</a>
20</div>
21
22<h2>NDEBUG</h2>
23
24<p><strong>Make sure you define NDEBUG</strong> The only way uBLAS
25knows you want a release configuration is to check if you have defined
26NDEBUG. If you don't it assumes you want a debug configuration and
27adds a lot of very useful runtime check. However these are very slow!
28</p>
29
30
31<h2>BOOST_UBLAS_MOVE_SEMANTICS</h2>
32
33<p class="credit">The patch and description was provided by Nasos Iliopoulos.</p>
34
35<p>An immediate effect of this option is the elimination of the need
36for noalias in types <tt>vector&lt;T&gt;</tt> and <tt>matrix&lt;T&gt;</tt>,
37when assigned to the same type. This option doesn't have an effect on
38bounded and c types. Although it is rare, not all compilers support copy
39elision (that allows for move semantics), so a test must be performed to
40make sure that there is a benefit when it is enabled. A small
41demonstration and test can be found in
42<a href="../test/manual/test_move_semantics.cpp"><tt>test_move_semantics.cpp</tt></a></p>
43
44<p>
45In the <a href="../test/manual/test_move_semantics.cpp">test
46example</a> two tests are defined, one for vectors and one for
47matrices. The aim of this example is to print the pointers of the
48storage of each of the containers, before and after the assignment to
49a temporary object. When move semantics are enabled, the
50<tt>vector&lt;T&gt;</tt> and <tt>matrix&lt;T&gt;</tt> storage is moved
51from the temporary and no copy is performed.
52</p>
53
54<p>
55If move semantics are supported by your compiler you will get an output like the following:
56</p>
57<pre class="screen">
58matrix&lt;double&gt; --------------------------------------------------------------------
59Temporary pointer r: 0x94790c0
60Pointer (must be equal to temp. pointer if move semantics are enabled) : 0x94790c0
61</pre>
62
63<p>Notes:</p>
64<ul>
65<li>It should be no surprise to see matrices and vectors been passed
66by VALUE, the compiler takes care and either moves (if the underlying
67code does not modify the object), or copies (if the underlying code
68modifies the object).
69</li>
70<li>There might be some space for some improvements (like clearing the
71data, before swaping)
72</li>
73<li>Move semantics don't eliminate temporaries. They rather move their
74storage around so no copies are performed.
75</li>
76<li>MSVC does no implement Named Return Value Optimization in debug
77mode. So if you build in debug with this compiler you might get <a
78href="https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=483229"
79target="_blank">different behaviour</a> than a release build.
80</li>
81<li>Enabling move semantics is done via #define BOOST_UBLAS_MOVE_SEMANTICS.
82</li>
83<li>There is plenty of room for optimizations when c++0x standard is
84out, taking advantage of rvalue references. (I have a sweet vector
85implementation using that).
86</li>
87<li>If you enable move semantics and your compiler does not support
88them, the operation will just be as passing by const reference.
89</li>
90</ul>
91
92<p>Interesting links</p>
93<ul>
94<li> <a href="http://cpp-next.com/archive/2009/08/want-speed-pass-by-value/" target="_blank">Want Speed? Pass by Value.</a>
95</li>
96<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>
97</li>
98<li> <a href="http://cpp-next.com/archive/2009/09/move-it-with-rvalue-references/" target="_blank">Move It With Rvalue References</a>
99</li>
100</ul>
101
102<h2>BOOST_UBLAS_CHECK_ENABLE</h2>
103
104<p>When BOOST_UBLAS_CHECK_ENABLE is defined then all index and
105parameter checks are enabled. This is enabled in debug mode and
106disabled in release mode.
107</p>
108
109<h2>BOOST_UBLAS_TYPE_CHECK</h2>
110
111<p>When BOOST_UBLAS_TYPE_CHECK is enabled then all possibly expensive
112structure checks are enabled. If this is not desireable then use
113<tt>#define BOOST_UBLAS_TYPE_CHECK 0</tt> before including any uBLAS
114header. The define BOOST_UBLAS_TYPE_CHECK_EPSILON can be used to
115control the acceptable tolerance, see
116<tt>detail/matrix_assign.hpp</tt> for implementation details of this
117check.
118</p>
119
120<h2>BOOST_UBLAS_USE_LONG_DOUBLE</h2>
121
122<p>Enable uBLAS expressions that involve containers of 'long double'</p>
123
124<h2>BOOST_UBLAS_USE_INTERVAL</h2>
125
126<p>Enable uBLAS expressions that involve containers of 'boost::numeric::interval' types</p>
127
128<h2>Configuring uBLAS with Macros</h2>
129
130<p>Many macro's appear in ublas/config.hpp and elsewhere. Hopefully in the future some of these will disappear!
131They fall into 4 groups:
132</p>
133<ul>
134<li> Automatically set by 'boost/numeric/ublas/config.hpp' based on
135NDEBUG. Makes the distinction between debug (safe) and release (fast)
136mode. Similar to STLport
137<ul>
138<li> <i>Release</i> mode (NDEBUG defined)
139<ul>
140<li> BOOST_UBLAS_INLINE <i>Compiler dependant definition to control
141function inlining.</i> </li><li> BOOST_UBLAS_USE_FAST_SAME </li></ul>
142</li><li> <i>Debug</i> mode
143<ul>
144<li> BOOST_UBLAS_CHECK_ENABLE <i>Enable checking of indexs, iterators
145and parameters. Prevents out of bound access etc.</i> </li><li>
146BOOST_UBLAS_TYPE_CHECK <i>Enable additional checks for the results of
147expressions using non dense types. Picks up runtime error such as the
148assignment of a numerically non-symmetric matrix to
149symmertic_matrix. Use <tt>#define BOOST_UBLAS_TYPE_CHECK 0</tt> to
150disable expensive numeric type checks.</i> (Note: "structure check"
151would be a much better name.) </li><li>
152BOOST_UBLAS_TYPE_CHECK_EPSILON <i>default: sqrt(epsilon), controls how
153large the difference between the expected result and the computed
154result may become. Increase this value if you are going to use near
155singular or badly scaled matrices. Please, refer to
156<tt>detail/matrix_assign.hpp</tt> for implementation of these type
157checks.</i> </li></ul> </li></ul>
158</li>
159<li> Automatically set by 'boost/numeric/ublas/config.hpp' based on
160compiler and boost/config.hpp macro's. Augments the compiler
161deficiency workarounds already supplied by boost/config.hpp
162<ul>
163<li> BOOST_UBLAS_NO_NESTED_CLASS_RELATION <i>A particularly nasty
164problem with VC7.1 Requires that uBLAS and the user use begin(it)
165rather then it.begin()</i> </li><li> BOOST_UBLAS_NO_SMART_PROXIES
166<i>Disable the automatic propagation of 'constantness' to
167proxies. Smart proxies automatically determine if the underling
168container they reference is constant or not. They adjust there
169definition of iterators and container access to reflect this
170constantness.</i> </li></ul>
171</li>
172<li> For use by uBLAS authors to test implementation methods. Preset
173in config.hpp
174<ul>
175<li> BOOST_UBLAS_USE_INVARIANT_HOISTING </li><li>
176BOOST_UBLAS_USE_INDEXING </li><li> BOOST_UBLAS_USE_INDEXED_ITERATOR
177</li><li> BOOST_UBLAS_NON_CONFORMANT_PROXIES <i>Gappy containers may
178be non-conformant, that is contain elements at different
179indices. Assigning between proxies (vector ranges for example) of
180these containers is difficult as the LHS may need insert new
181elements. This is slow.</i> </li><li> BOOST_UBLAS_USE_DUFF_DEVICE
182<i>Near useless on all platforms (see GCC's -funroll-loops)</i>
183
184</li></ul>
185</li>
186<li> User options. Can be predefined by user before including any
187uBLAS headers. They may also be automatically defined for some
188compilers to work around compile bugs.
189<ul>
190<li> BOOST_UBLAS_USE_LONG_DOUBLE <i>Enable uBLAS expressions that
191involve containers of 'long double'</i> </li><li>
192BOOST_UBLAS_USE_INTERVAL <i>Enable uBLAS expressions that involve
193containers of 'boost::numeric::interval' types</i> </li><li>
194BOOST_UBLAS_SIMPLE_ET_DEBUG <i>In order to simplify debugging is is
195possible to simplify expression templateso they are restricted to a
196single operation</i>
197
198</li><li> BOOST_UBLAS_ENABLE_PROXY_SHORTCUTS <i> enable automatic
199conversion from proxy class to matrix expression </i> </li><li>
200BOOST_UBLAS_NO_ELEMENT_PROXIES <i>Disables the use of element proxies
201for gappy types.</i> </li><li> <i>The Gappy types (sparse, coordinate,
202compressed) store non-zero elements in their own containers. When new
203non-zero elements are assigned they must rearrange these
204containers. This invalidates references, iterators or pointers to
205these elements. This can happen at some surprising times such as the
206expression "a [1] = a [0] = 1;". Element proxies guarantee all such
207expressions will work as expected. However they bring their own
208restrictions and efficiency problems. For example as of Boost 1.30.0
209they prevent the assignment of elements between different types.</i>
210</li>
211<li> BOOST_UBLAS_REFERENCE_CONST_MEMBER <i>Enable to allow refernces
212to be returned to fixed (zero or one) elements of triangular or banded
213matrices</i>
214
215</li><li> BOOST_UBLAS_NO_EXCEPTIONS <i>Disable the use exceptions of
216uBLAS internal checks and error conditions. BOOST_NO_EXCEPTIONS has
217same effect.</i>
218</li>
219<li> BOOST_UBLAS_SINGULAR_CHECK <i>Check the for singularity in triangular solve() functions</i></li>
220</ul>
221</li>
222</ul>
223
224<hr />
225<div id="copyright">
226 <p>Copyright (&copy;) 2000-2009 Joerg Walter, Mathias Koch, Gunter Winkler<br />
227 Use, modification and distribution are subject to the Boost Software License, Version 1.0.
228 (See accompanying file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt">
229 http://www.boost.org/LICENSE_1_0.txt
230 </a>).
231 </p>
232</div>
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234<p>
235<!-- Created: Wed Sep 16 21:19:20 CEST 2009 -->
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