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<a name="math_toolkit.main_faq"></a><a class="link" href="main_faq.html" title="Frequently Asked Questions FAQ">Frequently Asked Questions FAQ</a>
</h2></div></div></div>
<div class="orderedlist"><ol class="orderedlist" type="1">
<li class="listitem">
          <span class="emphasis"><em>I'm a FORTRAN/NAG/SPSS/SAS/Cephes/MathCad/R user and I don't
          see where the functions like dnorm(mean, sd) are in Boost.Math?</em></span>
          <br> Nearly all are provided, and many more like mean, skewness, quantiles,
          complements ... but Boost.Math makes full use of C++, and it looks a bit
          different. But do not panic! See section on construction and the many examples.
          Briefly, the distribution is constructed with the parameters (like location
          and scale) (things after the | in representation like P(X=k|n, p) or ;
          in a common represention of pdf f(x; &#956;&#963;<sup>2</sup>). Functions like pdf, cdf are called
          with the name of that distribution and the random variate often called
          x or k. For example, <code class="computeroutput"><span class="identifier">normal</span> <span class="identifier">my_norm</span><span class="special">(</span><span class="number">0</span><span class="special">,</span> <span class="number">1</span><span class="special">);</span> <span class="identifier">pdf</span><span class="special">(</span><span class="identifier">my_norm</span><span class="special">,</span> <span class="number">2.0</span><span class="special">);</span></code>
          <br>
        </li>
<li class="listitem">
          I'm a user of <a href="http://support.sas.com/rnd/app/da/new/probabilityfunctions.html" target="_top">New
          SAS Functions for Computing Probabilities</a>. <br> You will find
          the interface more familar, but to be able to select a distribution (perhaps
          using a string) see the Extras/Future Directions section, and /boost/libs/math/dot_net_example/boost_math.cpp
          for an example that is used to create a C# (C sharp) utility (that you
          might also find useful): see <a href="http://sourceforge.net/projects/distexplorer/" target="_top">Statistical
          Distribution Explorer</a>.<br>
        </li>
<li class="listitem">
          <span class="emphasis"><em>I'm allegic to reading manuals and prefer to learn from examples.</em></span><br>
          Fear not - you are not alone! Many examples are available for functions
          and distributions. Some are referenced directly from the text. Others can
          be found at \boost_latest_release\libs\math\example. If you are a Visual
          Studio user, you should be able to create projects from each of these,
          making sure that the Boost library is in the include directories list.
        </li>
<li class="listitem">
          <span class="emphasis"><em>How do I make sure that the Boost library is in the Visual Studio
          include directories list?</em></span><br> You can add an include path,
          for example, your Boost place /boost-latest_release, for example <code class="computeroutput"><span class="identifier">X</span><span class="special">:/</span><span class="identifier">boost_1_45_0</span><span class="special">/</span></code> if you have a separate partition X for
          Boost releases. Or you can use an environment variable BOOST_ROOT set to
          your Boost place, and include that. Visual Studio before 2010 provided
          Tools, Options, VC++ Directories to control directories: Visual Studio
          2010 instead provides property sheets to assist. You may find it convenient
          to create a new one adding \boost-latest_release; to the existing include
          items in $(IncludePath).
        </li>
<li class="listitem">
          <span class="emphasis"><em>I'm a FORTRAN/NAG/SPSS/SAS/Cephes/MathCad/R user and I don't
          see where the properties like mean, median, mode, variance, skewness of
          distributions are in Boost.Math?</em></span><br> They are all available
          (if defined for the parameters with which you constructed the distribution)
          via <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.cdf">Cumulative Distribution
          Function</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.pdf">Probability
          Density Function</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.quantile">Quantile</a>,
          <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.hazard">Hazard Function</a>,
          <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.chf">Cumulative Hazard Function</a>,
          <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.mean">mean</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.median">median</a>,
          <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.mode">mode</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.variance">variance</a>,
          <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.sd">standard deviation</a>,
          <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.skewness">skewness</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.kurtosis">kurtosis</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.kurtosis_excess">kurtosis_excess</a>,
          <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.range">range</a> and <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.support">support</a>.
        </li>
<li class="listitem">
          <span class="emphasis"><em>I am a C programmer. Can I user Boost.Math with C?</em></span><br>
          Yes you can, including all the special functions, and TR1 functions like
          isnan. They appear as C functions, by being declared as "extern C".
        </li>
<li class="listitem">
          <span class="emphasis"><em>I am a C# (Basic? F# FORTRAN? Other CLI?) programmer. Can I use
          Boost.Math with C#? (or ...)?</em></span> <br> Yes you can, including
          all the special functions, and TR1 functions like isnan. But you <span class="bold"><strong>must build the Boost.Math as a dynamic library (.dll) and compile
          with the /CLI option</strong></span>. See the boost/math/dot_net_example folder
          which contains an example that builds a simple statistical distribution
          app with a GUI. See <a href="http://sourceforge.net/projects/distexplorer/" target="_top">Statistical
          Distribution Explorer</a> <br>
        </li>
<li class="listitem">
          <span class="emphasis"><em>What these "policies" things for?</em></span> <br>
          Policies are a powerful (if necessarily complex) fine-grain mechanism that
          allow you to customise the behaviour of the Boost.Math library according
          to your precise needs. See <a class="link" href="../policy.html" title="Chapter&#160;15.&#160;Policies: Controlling Precision, Error Handling etc">Policies</a>. But
          if, very probably, the default behaviour suits you, you don't need to know
          more.
        </li>
<li class="listitem">
          <span class="emphasis"><em>I am a C user and expect to see global C-style<code class="computeroutput"><span class="special">::</span><span class="identifier">errno</span></code> set for overflow/errors etc?</em></span>
          <br> You can achieve what you want - see <a class="link" href="pol_ref/error_handling_policies.html" title="Error Handling Policies">error
          handling policies</a> and <a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">user
          error handling</a> and many examples.
        </li>
<li class="listitem">
          <span class="emphasis"><em>I am a C user and expect to silently return a max value for overflow?</em></span>
          <br> You (and C++ users too) can return whatever you want on overflow
          - see <a class="link" href="error_handling.html#math_toolkit.error_handling.overflow_error">overflow_error</a>
          and <a class="link" href="pol_ref/error_handling_policies.html" title="Error Handling Policies">error
          handling policies</a> and several examples.
        </li>
<li class="listitem">
          <span class="emphasis"><em>I don't want any error message for overflow etc?</em></span>
          <br> You can control exactly what happens for all the abnormal conditions,
          including the values returned. See <a class="link" href="error_handling.html#math_toolkit.error_handling.domain_error">domain_error</a>,
          <a class="link" href="error_handling.html#math_toolkit.error_handling.overflow_error">overflow_error</a>
          <a class="link" href="pol_ref/error_handling_policies.html" title="Error Handling Policies">error handling
          policies</a> <a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">user
          error handling</a> etc and examples.
        </li>
<li class="listitem">
          <span class="emphasis"><em>My environment doesn't allow and/or I don't want exceptions.
          Can I still user Boost.Math?</em></span> <br> Yes but you must customise
          the error handling: see <a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">user
          error handling</a> and <a class="link" href="pol_ref/policy_defaults.html" title="Using Macros to Change the Policy Defaults">changing
          policies defaults</a> .
        </li>
<li class="listitem">
          <span class="emphasis"><em>The docs are several hundreds of pages long! Can I read the docs
          off-line or on paper?</em></span> <br> Yes - you can download the Boost
          current release of most documentation as a zip of pdfs (including Boost.Math)
          from Sourceforge, for example <a href="https://sourceforge.net/projects/boost/files/boost-docs/1.45.0/boost_pdf_1_45_0.tar.gz/download" target="_top">https://sourceforge.net/projects/boost/files/boost-docs/1.45.0/boost_pdf_1_45_0.tar.gz/download</a>.
          And you can print any pages you need (or even print all pages - but be
          warned that there are several hundred!). Both html and pdf versions are
          highly hyperlinked. The entire Boost.Math pdf can be searched with Adobe
          Reader, Edit, Find ... This can often find what you seek, a partial substitute
          for a full index.
        </li>
<li class="listitem">
          <span class="emphasis"><em>I want a compact version for an embedded application. Can I use
          float precision?</em></span> <br> Yes - by selecting RealType template
          parameter as float: for example normal_distribution&lt;float&gt; your_normal(mean,
          sd); (But double may still be used internally, so space saving may be less
          that you hope for). You can also change the promotion policy, but accuracy
          might be much reduced.
        </li>
<li class="listitem">
          <span class="emphasis"><em>I seem to get somewhat different results compared to other programs.
          Why?</em></span> We hope Boost.Math to be more accurate: our priority is
          accuracy (over speed). See the section on accuracy. But for evaluations
          that require iterations there are parameters which can change the required
          accuracy (see <a class="link" href="../policy.html" title="Chapter&#160;15.&#160;Policies: Controlling Precision, Error Handling etc">Policies</a>). You might be able
          to squeeze a little more (or less) accuracy at the cost of runtime.
        </li>
<li class="listitem">
          <span class="emphasis"><em>Will my program run more slowly compared to other math functions
          and statistical libraries?</em></span> Probably, thought not always, and
          not by too much: our priority is accuracy. For most functions, making sure
          you have the latest compiler version with all optimisations switched on
          is the key to speed. For evaluations that require iteration, you may be
          able to gain a little more speed at the expense of accuracy. See detailed
          suggestions and results on <a class="link" href="../perf.html" title="Chapter&#160;16.&#160;Performance">performance</a>.
        </li>
<li class="listitem">
          <span class="emphasis"><em>How do I handle infinity and NaNs portably?</em></span> <br>
          See <a class="link" href="fp_facets.html" title="Facets for Floating-Point Infinities and NaNs">nonfinite fp_facets</a> for
          Facets for Floating-Point Infinities and NaNs.
        </li>
<li class="listitem">
          <span class="emphasis"><em>Where are the pre-built libraries?</em></span> <br> Good news
          - you probably don't need any! - just <code class="computeroutput"><span class="preprocessor">#include</span>
          <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span></code><span class="emphasis"><em>math/distribution_you_want&gt;</em></span>.
          But in the unlikely event that you do, see <a class="link" href="building.html" title="If and How to Build a Boost.Math Library, and its Examples and Tests">building
          libraries</a>.
        </li>
<li class="listitem">
          <span class="emphasis"><em>I don't see the function or distribution that I want.</em></span>
          <br> You could try an email to ask the authors - but no promises!
        </li>
<li class="listitem">
          <span class="emphasis"><em>I need more decimal digits for values/computations.</em></span>
          <br> You can use Boost.Math with <a href="../../../../../libs/multiprecision/doc/html/index.html" target="_top">Boost.Multiprecision</a>:
          typically <a href="../../../../../libs/multiprecision/doc/html/boost_multiprecision/tut/floats/cpp_dec_float.html" target="_top">cpp_dec_float</a>
          is a useful user-defined type to provide a fixed number of decimal digits,
          usually 50 or 100.
        </li>
<li class="listitem">
          Why can't I write something really simple like <code class="computeroutput"><span class="identifier">cpp_int</span>
          <span class="identifier">one</span><span class="special">(</span><span class="number">1</span><span class="special">);</span> <span class="identifier">cpp_dec_float_50</span>
          <span class="identifier">two</span><span class="special">(</span><span class="number">2</span><span class="special">);</span> <span class="identifier">one</span>
          <span class="special">*</span> <span class="identifier">two</span><span class="special">;</span></code> Because <code class="computeroutput"><span class="identifier">cpp_int</span></code>
          might be bigger than <code class="computeroutput"><span class="identifier">cpp_dec_float</span>
          <span class="identifier">can</span> <span class="identifier">hold</span></code>,
          so you must make an <span class="bold"><strong>explicit</strong></span> conversion.
          See <a href="http://svn.boost.org/svn/boost/trunk/libs/multiprecision/doc/html/boost_multiprecision/intro.html" target="_top">mixed
          multiprecision arithmetic</a> and <a href="http://svn.boost.org/svn/boost/trunk/libs/multiprecision/doc/html/boost_multiprecision/tut/conversions.html" target="_top">conversion</a>.
        </li>
</ol></div>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2006-2010, 2012-2014 Nikhar Agrawal,
      Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert
      Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Johan R&#229;de, Gautam Sewani,
      Benjamin Sobotta, Thijs van den Berg, Daryle Walker and Xiaogang Zhang<p>
        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>)
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	24	</div>
	25	<div class="section">
	26	<div class="titlepage"><div><div><h2 class="title" style="clear: both">
	27	<a name="math_toolkit.main_faq"></a><a class="link" href="main_faq.html" title="Frequently Asked Questions FAQ">Frequently Asked Questions FAQ</a>
	28	</h2></div></div></div>
	29	<div class="orderedlist"><ol class="orderedlist" type="1">
	30	<li class="listitem">
	31	<span class="emphasis"><em>I'm a FORTRAN/NAG/SPSS/SAS/Cephes/MathCad/R user and I don't
	32	see where the functions like dnorm(mean, sd) are in Boost.Math?</em></span>
	33	<br> Nearly all are provided, and many more like mean, skewness, quantiles,
	34	complements ... but Boost.Math makes full use of C++, and it looks a bit
	35	different. But do not panic! See section on construction and the many examples.
	36	Briefly, the distribution is constructed with the parameters (like location
	37	and scale) (things after the \| in representation like P(X=k\|n, p) or ;
	38	in a common represention of pdf f(x; μσ<sup>2</sup>). Functions like pdf, cdf are called
	39	with the name of that distribution and the random variate often called
	40	x or k. For example, <code class="computeroutput"><span class="identifier">normal</span> <span class="identifier">my_norm</span><span class="special">(</span><span class="number">0</span><span class="special">,</span> <span class="number">1</span><span class="special">);</span> <span class="identifier">pdf</span><span class="special">(</span><span class="identifier">my_norm</span><span class="special">,</span> <span class="number">2.0</span><span class="special">);</span></code>
	41	<br>
	42	</li>
	43	<li class="listitem">
	44	I'm a user of <a href="http://support.sas.com/rnd/app/da/new/probabilityfunctions.html" target="_top">New
	45	SAS Functions for Computing Probabilities</a>. <br> You will find
	46	the interface more familar, but to be able to select a distribution (perhaps
	47	using a string) see the Extras/Future Directions section, and /boost/libs/math/dot_net_example/boost_math.cpp
	48	for an example that is used to create a C# (C sharp) utility (that you
	49	might also find useful): see <a href="http://sourceforge.net/projects/distexplorer/" target="_top">Statistical
	50	Distribution Explorer</a>.<br>
	51	</li>
	52	<li class="listitem">
	53	<span class="emphasis"><em>I'm allegic to reading manuals and prefer to learn from examples.</em></span><br>
	54	Fear not - you are not alone! Many examples are available for functions
	55	and distributions. Some are referenced directly from the text. Others can
	56	be found at \boost_latest_release\libs\math\example. If you are a Visual
	57	Studio user, you should be able to create projects from each of these,
	58	making sure that the Boost library is in the include directories list.
	59	</li>
	60	<li class="listitem">
	61	<span class="emphasis"><em>How do I make sure that the Boost library is in the Visual Studio
	62	include directories list?</em></span><br> You can add an include path,
	63	for example, your Boost place /boost-latest_release, for example <code class="computeroutput"><span class="identifier">X</span><span class="special">:/</span><span class="identifier">boost_1_45_0</span><span class="special">/</span></code> if you have a separate partition X for
	64	Boost releases. Or you can use an environment variable BOOST_ROOT set to
65	your Boost place, and include that. Visual Studio before 2010 provided
66	Tools, Options, VC++ Directories to control directories: Visual Studio
67	2010 instead provides property sheets to assist. You may find it convenient
68	to create a new one adding \boost-latest_release; to the existing include
69	items in $(IncludePath).
70	</li>
71	<li class="listitem">
72	<span class="emphasis"><em>I'm a FORTRAN/NAG/SPSS/SAS/Cephes/MathCad/R user and I don't
73	see where the properties like mean, median, mode, variance, skewness of
74	distributions are in Boost.Math?</em></span><br> They are all available
75	(if defined for the parameters with which you constructed the distribution)
76	via <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.cdf">Cumulative Distribution
77	Function</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.pdf">Probability
78	Density Function</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.quantile">Quantile</a>,
79	<a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.hazard">Hazard Function</a>,
80	<a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.chf">Cumulative Hazard Function</a>,
81	<a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.mean">mean</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.median">median</a>,
82	<a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.mode">mode</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.variance">variance</a>,
83	<a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.sd">standard deviation</a>,
84	<a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.skewness">skewness</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.kurtosis">kurtosis</a>, <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.kurtosis_excess">kurtosis_excess</a>,
85	<a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.range">range</a> and <a class="link" href="dist_ref/nmp.html#math_toolkit.dist_ref.nmp.support">support</a>.
86	</li>
87	<li class="listitem">
88	<span class="emphasis"><em>I am a C programmer. Can I user Boost.Math with C?</em></span><br>
89	Yes you can, including all the special functions, and TR1 functions like
90	isnan. They appear as C functions, by being declared as "extern C".
91	</li>
92	<li class="listitem">
93	<span class="emphasis"><em>I am a C# (Basic? F# FORTRAN? Other CLI?) programmer. Can I use
94	Boost.Math with C#? (or ...)?</em></span> <br> Yes you can, including
95	all the special functions, and TR1 functions like isnan. But you <span class="bold"><strong>must build the Boost.Math as a dynamic library (.dll) and compile
96	with the /CLI option</strong></span>. See the boost/math/dot_net_example folder
97	which contains an example that builds a simple statistical distribution
98	app with a GUI. See <a href="http://sourceforge.net/projects/distexplorer/" target="_top">Statistical
99	Distribution Explorer</a> <br>
100	</li>
101	<li class="listitem">
102	<span class="emphasis"><em>What these "policies" things for?</em></span> <br>
103	Policies are a powerful (if necessarily complex) fine-grain mechanism that
104	allow you to customise the behaviour of the Boost.Math library according
105	to your precise needs. See <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policies</a>. But
106	if, very probably, the default behaviour suits you, you don't need to know
107	more.
108	</li>
109	<li class="listitem">
110	<span class="emphasis"><em>I am a C user and expect to see global C-style<code class="computeroutput"><span class="special">::</span><span class="identifier">errno</span></code> set for overflow/errors etc?</em></span>
111	<br> You can achieve what you want - see <a class="link" href="pol_ref/error_handling_policies.html" title="Error Handling Policies">error
112	handling policies</a> and <a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">user
113	error handling</a> and many examples.
114	</li>
115	<li class="listitem">
116	<span class="emphasis"><em>I am a C user and expect to silently return a max value for overflow?</em></span>
117	<br> You (and C++ users too) can return whatever you want on overflow
118	- see <a class="link" href="error_handling.html#math_toolkit.error_handling.overflow_error">overflow_error</a>
119	and <a class="link" href="pol_ref/error_handling_policies.html" title="Error Handling Policies">error
120	handling policies</a> and several examples.
121	</li>
122	<li class="listitem">
123	<span class="emphasis"><em>I don't want any error message for overflow etc?</em></span>
124	<br> You can control exactly what happens for all the abnormal conditions,
125	including the values returned. See <a class="link" href="error_handling.html#math_toolkit.error_handling.domain_error">domain_error</a>,
126	<a class="link" href="error_handling.html#math_toolkit.error_handling.overflow_error">overflow_error</a>
127	<a class="link" href="pol_ref/error_handling_policies.html" title="Error Handling Policies">error handling
128	policies</a> <a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">user
129	error handling</a> etc and examples.
130	</li>
131	<li class="listitem">
132	<span class="emphasis"><em>My environment doesn't allow and/or I don't want exceptions.
133	Can I still user Boost.Math?</em></span> <br> Yes but you must customise
134	the error handling: see <a class="link" href="pol_tutorial/user_def_err_pol.html" title="Calling User Defined Error Handlers">user
135	error handling</a> and <a class="link" href="pol_ref/policy_defaults.html" title="Using Macros to Change the Policy Defaults">changing
136	policies defaults</a> .
137	</li>
138	<li class="listitem">
139	<span class="emphasis"><em>The docs are several hundreds of pages long! Can I read the docs
140	off-line or on paper?</em></span> <br> Yes - you can download the Boost
141	current release of most documentation as a zip of pdfs (including Boost.Math)
142	from Sourceforge, for example <a href="https://sourceforge.net/projects/boost/files/boost-docs/1.45.0/boost_pdf_1_45_0.tar.gz/download" target="_top">https://sourceforge.net/projects/boost/files/boost-docs/1.45.0/boost_pdf_1_45_0.tar.gz/download</a>.
143	And you can print any pages you need (or even print all pages - but be
144	warned that there are several hundred!). Both html and pdf versions are
145	highly hyperlinked. The entire Boost.Math pdf can be searched with Adobe
146	Reader, Edit, Find ... This can often find what you seek, a partial substitute
147	for a full index.
148	</li>
149	<li class="listitem">
150	<span class="emphasis"><em>I want a compact version for an embedded application. Can I use
151	float precision?</em></span> <br> Yes - by selecting RealType template
152	parameter as float: for example normal_distribution<float> your_normal(mean,
153	sd); (But double may still be used internally, so space saving may be less
154	that you hope for). You can also change the promotion policy, but accuracy
155	might be much reduced.
156	</li>
157	<li class="listitem">
158	<span class="emphasis"><em>I seem to get somewhat different results compared to other programs.
159	Why?</em></span> We hope Boost.Math to be more accurate: our priority is
160	accuracy (over speed). See the section on accuracy. But for evaluations
161	that require iterations there are parameters which can change the required
162	accuracy (see <a class="link" href="../policy.html" title="Chapter 15. Policies: Controlling Precision, Error Handling etc">Policies</a>). You might be able
163	to squeeze a little more (or less) accuracy at the cost of runtime.
164	</li>
165	<li class="listitem">
166	<span class="emphasis"><em>Will my program run more slowly compared to other math functions
167	and statistical libraries?</em></span> Probably, thought not always, and
168	not by too much: our priority is accuracy. For most functions, making sure
169	you have the latest compiler version with all optimisations switched on
170	is the key to speed. For evaluations that require iteration, you may be
171	able to gain a little more speed at the expense of accuracy. See detailed
172	suggestions and results on <a class="link" href="../perf.html" title="Chapter 16. Performance">performance</a>.
173	</li>
174	<li class="listitem">
175	<span class="emphasis"><em>How do I handle infinity and NaNs portably?</em></span> <br>
176	See <a class="link" href="fp_facets.html" title="Facets for Floating-Point Infinities and NaNs">nonfinite fp_facets</a> for
177	Facets for Floating-Point Infinities and NaNs.
178	</li>
179	<li class="listitem">
180	<span class="emphasis"><em>Where are the pre-built libraries?</em></span> <br> Good news
181	- you probably don't need any! - just <code class="computeroutput"><span class="preprocessor">#include</span>
182	<span class="special"><</span><span class="identifier">boost</span><span class="special">/</span></code><span class="emphasis"><em>math/distribution_you_want></em></span>.
183	But in the unlikely event that you do, see <a class="link" href="building.html" title="If and How to Build a Boost.Math Library, and its Examples and Tests">building
184	libraries</a>.
185	</li>
186	<li class="listitem">
187	<span class="emphasis"><em>I don't see the function or distribution that I want.</em></span>
188	<br> You could try an email to ask the authors - but no promises!
189	</li>
190	<li class="listitem">
191	<span class="emphasis"><em>I need more decimal digits for values/computations.</em></span>
192	<br> You can use Boost.Math with <a href="../../../../../libs/multiprecision/doc/html/index.html" target="_top">Boost.Multiprecision</a>:
193	typically <a href="../../../../../libs/multiprecision/doc/html/boost_multiprecision/tut/floats/cpp_dec_float.html" target="_top">cpp_dec_float</a>
194	is a useful user-defined type to provide a fixed number of decimal digits,
195	usually 50 or 100.
196	</li>
197	<li class="listitem">
198	Why can't I write something really simple like <code class="computeroutput"><span class="identifier">cpp_int</span>
199	<span class="identifier">one</span><span class="special">(</span><span class="number">1</span><span class="special">);</span> <span class="identifier">cpp_dec_float_50</span>
200	<span class="identifier">two</span><span class="special">(</span><span class="number">2</span><span class="special">);</span> <span class="identifier">one</span>
201	<span class="special">*</span> <span class="identifier">two</span><span class="special">;</span></code> Because <code class="computeroutput"><span class="identifier">cpp_int</span></code>
202	might be bigger than <code class="computeroutput"><span class="identifier">cpp_dec_float</span>
203	<span class="identifier">can</span> <span class="identifier">hold</span></code>,
204	so you must make an <span class="bold"><strong>explicit</strong></span> conversion.
205	See <a href="http://svn.boost.org/svn/boost/trunk/libs/multiprecision/doc/html/boost_multiprecision/intro.html" target="_top">mixed
206	multiprecision arithmetic</a> and <a href="http://svn.boost.org/svn/boost/trunk/libs/multiprecision/doc/html/boost_multiprecision/tut/conversions.html" target="_top">conversion</a>.
207	</li>
208	</ol></div>
209	</div>
210	<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
211	<td align="left"></td>
212	<td align="right"><div class="copyright-footer">Copyright © 2006-2010, 2012-2014 Nikhar Agrawal,
213	Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert
214	Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Johan Råde, Gautam Sewani,
215	Benjamin Sobotta, Thijs van den Berg, Daryle Walker and Xiaogang Zhang<p>
216	Distributed under the Boost Software License, Version 1.0. (See accompanying
217	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>)
218	</p>
219	</div></td>
220	</tr></table>
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