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<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>Implementation of Float128 type</title> <link rel="stylesheet" href="../math.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.78.1"> <link rel="home" href="../index.html" title="Math Toolkit 2.1.0"> <link rel="up" href="../cstdfloat.html" title="Chapter 3. Specified-width floating-point typedefs"> <link rel="prev" href="examples.html" title="Examples"> <link rel="next" href="float128/overloading_template_functions_w.html" title="Overloading template functions with float128_t"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table cellpadding="2" width="100%"><tr> <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td> <td align="center"><a href="../../../../../index.html">Home</a></td> <td align="center"><a href="../../../../../libs/libraries.htm">Libraries</a></td> <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> <td align="center"><a href="../../../../../more/index.htm">More</a></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="examples.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../cstdfloat.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="float128/overloading_template_functions_w.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> </div> <div class="section"> <div class="titlepage"><div><div><h2 class="title" style="clear: both"> <a name="math_toolkit.float128"></a><a class="link" href="float128.html" title="Implementation of Float128 type">Implementation of Float128 type</a> </h2></div></div></div> <div class="toc"><dl class="toc"> <dt><a href="float128/overloading_template_functions_w.html">Overloading template functions with float128_t</a></dt> <dt><a href="float128/exp_function.html">Exponential function</a></dt> <dt><a href="float128/typeinfo.html"><code class="computeroutput">typeinfo</code></a></dt> </dl></div> Since few compilers implement a true 128-bit floating-point, and language features like the suffix Q, and C++ Standard library functions are as-yet missing or incomplete in C++11, this Boost.Math implementation wraps <code class="computeroutput">__float128</code> provided by the GCC compiler or the <code class="computeroutput">_Quad</code> type provided by the Intel compiler. This is provided to in order to demonstrate, and users to evaluate, the feasibility and benefits of higher-precision floating-point, especially to allow use of the full Boost.Math library of functions and distributions at high precision. (It is also possible to use Boost.Math with Boost.Multiprecision decimal and binary, but since these are entirely software solutions, allowing much higher precision or arbitrary precision, they are likely to be slower). We also provide (we believe full) support for <code class="computeroutput"><limits>, <cmath></code>, I/O stream operations in <code class="computeroutput"><iostream></code>, and <code class="computeroutput"><complex></code>. As a prototype for a future C++ standard, we place all these in <code class="computeroutput">namespace std</code>. This contravenes the existing C++ standard of course, so selecting any compiler that promises to check conformance will fail. <div class="tip"><table border="0" summary="Tip"> <tr> <td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../../../doc/src/images/tip.png"></td> <th align="left">Tip</th> </tr> <tr><td align="left" valign="top"> For GCC, compile with <code class="computeroutput">-std=gnu++11</code> or <code class="computeroutput">-std=gnu++03</code> and do not use <code class="computeroutput">-std=stdc++11</code>or any 'strict' options as these turn off full support for <code class="computeroutput">__float128</code>. These requirements also apply to the Intel compiler on Linux, for Intel on Windows you need to compile with <code class="computeroutput">-Qoption,cpp,--extended_float_type -DBOOST_MATH_USE_FLOAT128</code> in order to activate 128-bit floating point support. </td></tr> </table></div> The <code class="computeroutput">__float128</code> type is provided by the <a href="http://gcc.gnu.org/onlinedocs/libquadmath/" target="_top">libquadmath library</a> on GCC or by Intel's FORTRAN library with Intel C++. A typical invocation of the compiler is <pre class="programlisting">g++ -O3 -std=gnu++11 test.cpp -I/c/modular-boost -lquadmath -o test.exe </pre> <div class="tip"><table border="0" summary="Tip"> <tr> <td rowspan="2" align="center" valign="top" width="25"><img alt="[Tip]" src="../../../../../doc/src/images/tip.png"></td> <th align="left">Tip</th> </tr> <tr><td align="left" valign="top"> If you are trying to use the develop branch of Boost.Math, then make <code class="computeroutput">-I/c/modular-boost/libs/math/include</code> the first include directory. </td></tr> </table></div> <pre class="programlisting">g++ -O3 -std=gnu++11 test.cpp -I/c/modular-boost/libs/math/include -I/c/modular-boost -lquadmath -o test.exe </pre> <div class="note"><table border="0" summary="Note"> <tr> <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/src/images/note.png"></td> <th align="left">Note</th> </tr> <tr><td align="left" valign="top"> So far, the only missing detail that we have noted is in trying to use <code class="computeroutput"><typeinfo></code>, for example for <code class="computeroutput">std::cout << typeid<__float_128>.name();</code>. Link fails: undefined reference to <code class="computeroutput">typeinfo for __float128</code>. See <a href="http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43622" target="_top">GCC Bug 43622 - no C++ typeinfo for __float128</a>. </td></tr> </table></div> </div> <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> <td align="left"></td> <td align="right"><div class="copyright-footer">Copyright © 2006-2010, 2012-2014 Nikhar Agrawal, Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert Holin, Bruno Lalande, John Maddock, Johan Råde, Gautam Sewani, Benjamin Sobotta, Thijs van den Berg, Daryle Walker and Xiaogang Zhang Distributed under 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" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) </div></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="examples.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../cstdfloat.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="float128/overloading_template_functions_w.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> </div> </body> </html>