1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Self expanding lattices</title> 5<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../index.html" title="Chapter 1. Boost.Numeric.Odeint"> 8<link rel="up" href="../tutorial.html" title="Tutorial"> 9<link rel="prev" href="using_arbitrary_precision_floating_point_types.html" title="Using arbitrary precision floating point types"> 10<link rel="next" href="using_cuda__or_openmp__tbb_______via_thrust.html" title="Using CUDA (or OpenMP, TBB, ...) via Thrust"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../logo.jpg"></td> 15<td align="center"><a href="../../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="using_arbitrary_precision_floating_point_types.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../tutorial.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="using_cuda__or_openmp__tbb_______via_thrust.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h3 class="title"> 27<a name="boost_numeric_odeint.tutorial.self_expanding_lattices"></a><a class="link" href="self_expanding_lattices.html" title="Self expanding lattices">Self 28 expanding lattices</a> 29</h3></div></div></div> 30<p> 31 odeint supports changes of the state size during integration if a state_type 32 is used which can be resized, like <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span></code>. 33 The adjustment of the state's size has to be done from outside and the stepper 34 has to be instantiated with <code class="computeroutput"><span class="identifier">always_resizer</span></code> 35 as the template argument for the <code class="computeroutput"><span class="identifier">resizer_type</span></code>. 36 In this configuration, the stepper checks for changes in the state size and 37 adjust it's internal storage accordingly. 38 </p> 39<p> 40 We show this for a Hamiltonian system of nonlinear, disordered oscillators 41 with nonlinear nearest neighbor coupling. 42 </p> 43<p> 44 The system function is implemented in terms of a class that also provides 45 functions for calculating the energy. Note, that this class stores the random 46 potential internally which is not resized, but rather a start index is kept 47 which should be changed whenever the states' size change. 48 </p> 49<p> 50</p> 51<pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">vector</span><span class="special"><</span> <span class="keyword">double</span> <span class="special">></span> <span class="identifier">coord_type</span><span class="special">;</span> 52<span class="keyword">typedef</span> <span class="identifier">pair</span><span class="special"><</span> <span class="identifier">coord_type</span> <span class="special">,</span> <span class="identifier">coord_type</span> <span class="special">></span> <span class="identifier">state_type</span><span class="special">;</span> 53 54<span class="keyword">struct</span> <span class="identifier">compacton_lattice</span> 55<span class="special">{</span> 56 <span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">m_max_N</span><span class="special">;</span> 57 <span class="keyword">const</span> <span class="keyword">double</span> <span class="identifier">m_beta</span><span class="special">;</span> 58 <span class="keyword">int</span> <span class="identifier">m_pot_start_index</span><span class="special">;</span> 59 <span class="identifier">vector</span><span class="special"><</span> <span class="keyword">double</span> <span class="special">></span> <span class="identifier">m_pot</span><span class="special">;</span> 60 61 <span class="identifier">compacton_lattice</span><span class="special">(</span> <span class="keyword">int</span> <span class="identifier">max_N</span> <span class="special">,</span> <span class="keyword">double</span> <span class="identifier">beta</span> <span class="special">,</span> <span class="keyword">int</span> <span class="identifier">pot_start_index</span> <span class="special">)</span> 62 <span class="special">:</span> <span class="identifier">m_max_N</span><span class="special">(</span> <span class="identifier">max_N</span> <span class="special">)</span> <span class="special">,</span> <span class="identifier">m_beta</span><span class="special">(</span> <span class="identifier">beta</span> <span class="special">)</span> <span class="special">,</span> <span class="identifier">m_pot_start_index</span><span class="special">(</span> <span class="identifier">pot_start_index</span> <span class="special">)</span> <span class="special">,</span> <span class="identifier">m_pot</span><span class="special">(</span> <span class="identifier">max_N</span> <span class="special">)</span> 63 <span class="special">{</span> 64 <span class="identifier">srand</span><span class="special">(</span> <span class="identifier">time</span><span class="special">(</span> <span class="identifier">NULL</span> <span class="special">)</span> <span class="special">);</span> 65 <span class="comment">// fill random potential with iid values from [0,1]</span> 66 <span class="identifier">boost</span><span class="special">::</span><span class="identifier">mt19937</span> <span class="identifier">rng</span><span class="special">;</span> 67 <span class="identifier">boost</span><span class="special">::</span><span class="identifier">uniform_real</span><span class="special"><></span> <span class="identifier">unif</span><span class="special">(</span> <span class="number">0.0</span> <span class="special">,</span> <span class="number">1.0</span> <span class="special">);</span> 68 <span class="identifier">boost</span><span class="special">::</span><span class="identifier">variate_generator</span><span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">mt19937</span><span class="special">&,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">uniform_real</span><span class="special"><></span> <span class="special">></span> <span class="identifier">gen</span><span class="special">(</span> <span class="identifier">rng</span> <span class="special">,</span> <span class="identifier">unif</span> <span class="special">);</span> 69 <span class="identifier">generate</span><span class="special">(</span> <span class="identifier">m_pot</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()</span> <span class="special">,</span> <span class="identifier">m_pot</span><span class="special">.</span><span class="identifier">end</span><span class="special">()</span> <span class="special">,</span> <span class="identifier">gen</span> <span class="special">);</span> 70 <span class="special">}</span> 71 72 <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()(</span> <span class="keyword">const</span> <span class="identifier">coord_type</span> <span class="special">&</span><span class="identifier">q</span> <span class="special">,</span> <span class="identifier">coord_type</span> <span class="special">&</span><span class="identifier">dpdt</span> <span class="special">)</span> 73 <span class="special">{</span> 74 <span class="comment">// calculate dpdt = -dH/dq of this hamiltonian system</span> 75 <span class="comment">// dp_i/dt = - V_i * q_i^3 - beta*(q_i - q_{i-1})^3 + beta*(q_{i+1} - q_i)^3</span> 76 <span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">N</span> <span class="special">=</span> <span class="identifier">q</span><span class="special">.</span><span class="identifier">size</span><span class="special">();</span> 77 <span class="keyword">double</span> <span class="identifier">diff</span> <span class="special">=</span> <span class="identifier">q</span><span class="special">[</span><span class="number">0</span><span class="special">]</span> <span class="special">-</span> <span class="identifier">q</span><span class="special">[</span><span class="identifier">N</span><span class="special">-</span><span class="number">1</span><span class="special">];</span> 78 <span class="keyword">for</span><span class="special">(</span> <span class="keyword">int</span> <span class="identifier">i</span><span class="special">=</span><span class="number">0</span> <span class="special">;</span> <span class="identifier">i</span><span class="special"><</span><span class="identifier">N</span> <span class="special">;</span> <span class="special">++</span><span class="identifier">i</span> <span class="special">)</span> 79 <span class="special">{</span> 80 <span class="identifier">dpdt</span><span class="special">[</span><span class="identifier">i</span><span class="special">]</span> <span class="special">=</span> <span class="special">-</span> <span class="identifier">m_pot</span><span class="special">[</span><span class="identifier">m_pot_start_index</span><span class="special">+</span><span class="identifier">i</span><span class="special">]</span> <span class="special">*</span> <span class="identifier">q</span><span class="special">[</span><span class="identifier">i</span><span class="special">]*</span><span class="identifier">q</span><span class="special">[</span><span class="identifier">i</span><span class="special">]*</span><span class="identifier">q</span><span class="special">[</span><span class="identifier">i</span><span class="special">]</span> <span class="special">-</span> 81 <span class="identifier">m_beta</span> <span class="special">*</span> <span class="identifier">diff</span><span class="special">*</span><span class="identifier">diff</span><span class="special">*</span><span class="identifier">diff</span><span class="special">;</span> 82 <span class="identifier">diff</span> <span class="special">=</span> <span class="identifier">q</span><span class="special">[(</span><span class="identifier">i</span><span class="special">+</span><span class="number">1</span><span class="special">)</span> <span class="special">%</span> <span class="identifier">N</span><span class="special">]</span> <span class="special">-</span> <span class="identifier">q</span><span class="special">[</span><span class="identifier">i</span><span class="special">];</span> 83 <span class="identifier">dpdt</span><span class="special">[</span><span class="identifier">i</span><span class="special">]</span> <span class="special">+=</span> <span class="identifier">m_beta</span> <span class="special">*</span> <span class="identifier">diff</span><span class="special">*</span><span class="identifier">diff</span><span class="special">*</span><span class="identifier">diff</span><span class="special">;</span> 84 <span class="special">}</span> 85 <span class="special">}</span> 86 87 <span class="keyword">void</span> <span class="identifier">energy_distribution</span><span class="special">(</span> <span class="keyword">const</span> <span class="identifier">coord_type</span> <span class="special">&</span><span class="identifier">q</span> <span class="special">,</span> <span class="keyword">const</span> <span class="identifier">coord_type</span> <span class="special">&</span><span class="identifier">p</span> <span class="special">,</span> <span class="identifier">coord_type</span> <span class="special">&</span><span class="identifier">energies</span> <span class="special">)</span> 88 <span class="special">{</span> 89 <span class="comment">// computes the energy per lattice site normalized by total energy</span> 90 <span class="keyword">const</span> <span class="identifier">size_t</span> <span class="identifier">N</span> <span class="special">=</span> <span class="identifier">q</span><span class="special">.</span><span class="identifier">size</span><span class="special">();</span> 91 <span class="keyword">double</span> <span class="identifier">en</span> <span class="special">=</span> <span class="number">0.0</span><span class="special">;</span> 92 <span class="keyword">for</span><span class="special">(</span> <span class="identifier">size_t</span> <span class="identifier">i</span><span class="special">=</span><span class="number">0</span> <span class="special">;</span> <span class="identifier">i</span><span class="special"><</span><span class="identifier">N</span> <span class="special">;</span> <span class="identifier">i</span><span class="special">++</span> <span class="special">)</span> 93 <span class="special">{</span> 94 <span class="keyword">const</span> <span class="keyword">double</span> <span class="identifier">diff</span> <span class="special">=</span> <span class="identifier">q</span><span class="special">[(</span><span class="identifier">i</span><span class="special">+</span><span class="number">1</span><span class="special">)</span> <span class="special">%</span> <span class="identifier">N</span><span class="special">]</span> <span class="special">-</span> <span class="identifier">q</span><span class="special">[</span><span class="identifier">i</span><span class="special">];</span> 95 <span class="identifier">energies</span><span class="special">[</span><span class="identifier">i</span><span class="special">]</span> <span class="special">=</span> <span class="identifier">p</span><span class="special">[</span><span class="identifier">i</span><span class="special">]*</span><span class="identifier">p</span><span class="special">[</span><span class="identifier">i</span><span class="special">]/</span><span class="number">2.0</span> 96 <span class="special">+</span> <span class="identifier">m_pot</span><span class="special">[</span><span class="identifier">m_pot_start_index</span><span class="special">+</span><span class="identifier">i</span><span class="special">]*</span><span class="identifier">q</span><span class="special">[</span><span class="identifier">i</span><span class="special">]*</span><span class="identifier">q</span><span class="special">[</span><span class="identifier">i</span><span class="special">]*</span><span class="identifier">q</span><span class="special">[</span><span class="identifier">i</span><span class="special">]*</span><span class="identifier">q</span><span class="special">[</span><span class="identifier">i</span><span class="special">]/</span><span class="number">4.0</span> 97 <span class="special">+</span> <span class="identifier">m_beta</span><span class="special">/</span><span class="number">4.0</span> <span class="special">*</span> <span class="identifier">diff</span><span class="special">*</span><span class="identifier">diff</span><span class="special">*</span><span class="identifier">diff</span><span class="special">*</span><span class="identifier">diff</span><span class="special">;</span> 98 <span class="identifier">en</span> <span class="special">+=</span> <span class="identifier">energies</span><span class="special">[</span><span class="identifier">i</span><span class="special">];</span> 99 <span class="special">}</span> 100 <span class="identifier">en</span> <span class="special">=</span> <span class="number">1.0</span><span class="special">/</span><span class="identifier">en</span><span class="special">;</span> 101 <span class="keyword">for</span><span class="special">(</span> <span class="identifier">size_t</span> <span class="identifier">i</span><span class="special">=</span><span class="number">0</span> <span class="special">;</span> <span class="identifier">i</span><span class="special"><</span><span class="identifier">N</span> <span class="special">;</span> <span class="identifier">i</span><span class="special">++</span> <span class="special">)</span> 102 <span class="special">{</span> 103 <span class="identifier">energies</span><span class="special">[</span><span class="identifier">i</span><span class="special">]</span> <span class="special">*=</span> <span class="identifier">en</span><span class="special">;</span> 104 <span class="special">}</span> 105 <span class="special">}</span> 106 107 <span class="keyword">double</span> <span class="identifier">energy</span><span class="special">(</span> <span class="keyword">const</span> <span class="identifier">coord_type</span> <span class="special">&</span><span class="identifier">q</span> <span class="special">,</span> <span class="keyword">const</span> <span class="identifier">coord_type</span> <span class="special">&</span><span class="identifier">p</span> <span class="special">)</span> 108 <span class="special">{</span> 109 <span class="comment">// calculates the total energy of the excitation</span> 110 <span class="keyword">const</span> <span class="identifier">size_t</span> <span class="identifier">N</span> <span class="special">=</span> <span class="identifier">q</span><span class="special">.</span><span class="identifier">size</span><span class="special">();</span> 111 <span class="keyword">double</span> <span class="identifier">en</span> <span class="special">=</span> <span class="number">0.0</span><span class="special">;</span> 112 <span class="keyword">for</span><span class="special">(</span> <span class="identifier">size_t</span> <span class="identifier">i</span><span class="special">=</span><span class="number">0</span> <span class="special">;</span> <span class="identifier">i</span><span class="special"><</span><span class="identifier">N</span> <span class="special">;</span> <span class="identifier">i</span><span class="special">++</span> <span class="special">)</span> 113 <span class="special">{</span> 114 <span class="keyword">const</span> <span class="keyword">double</span> <span class="identifier">diff</span> <span class="special">=</span> <span class="identifier">q</span><span class="special">[(</span><span class="identifier">i</span><span class="special">+</span><span class="number">1</span><span class="special">)</span> <span class="special">%</span> <span class="identifier">N</span><span class="special">]</span> <span class="special">-</span> <span class="identifier">q</span><span class="special">[</span><span class="identifier">i</span><span class="special">];</span> 115 <span class="identifier">en</span> <span class="special">+=</span> <span class="identifier">p</span><span class="special">[</span><span class="identifier">i</span><span class="special">]*</span><span class="identifier">p</span><span class="special">[</span><span class="identifier">i</span><span class="special">]/</span><span class="number">2.0</span> 116 <span class="special">+</span> <span class="identifier">m_pot</span><span class="special">[</span><span class="identifier">m_pot_start_index</span><span class="special">+</span><span class="identifier">i</span><span class="special">]*</span><span class="identifier">q</span><span class="special">[</span><span class="identifier">i</span><span class="special">]*</span><span class="identifier">q</span><span class="special">[</span><span class="identifier">i</span><span class="special">]*</span><span class="identifier">q</span><span class="special">[</span><span class="identifier">i</span><span class="special">]*</span><span class="identifier">q</span><span class="special">[</span><span class="identifier">i</span><span class="special">]</span> <span class="special">/</span> <span class="number">4.0</span> 117 <span class="special">+</span> <span class="identifier">m_beta</span><span class="special">/</span><span class="number">4.0</span> <span class="special">*</span> <span class="identifier">diff</span><span class="special">*</span><span class="identifier">diff</span><span class="special">*</span><span class="identifier">diff</span><span class="special">*</span><span class="identifier">diff</span><span class="special">;</span> 118 <span class="special">}</span> 119 <span class="keyword">return</span> <span class="identifier">en</span><span class="special">;</span> 120 <span class="special">}</span> 121 122 <span class="keyword">void</span> <span class="identifier">change_pot_start</span><span class="special">(</span> <span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">delta</span> <span class="special">)</span> 123 <span class="special">{</span> 124 <span class="identifier">m_pot_start_index</span> <span class="special">+=</span> <span class="identifier">delta</span><span class="special">;</span> 125 <span class="special">}</span> 126<span class="special">};</span> 127</pre> 128<p> 129 </p> 130<p> 131 The total size we allow is 1024 and we start with an initial state size of 132 60. 133 </p> 134<p> 135</p> 136<pre class="programlisting"><span class="comment">//start with 60 sites</span> 137<span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">N_start</span> <span class="special">=</span> <span class="number">60</span><span class="special">;</span> 138<span class="identifier">coord_type</span> <span class="identifier">q</span><span class="special">(</span> <span class="identifier">N_start</span> <span class="special">,</span> <span class="number">0.0</span> <span class="special">);</span> 139<span class="identifier">q</span><span class="special">.</span><span class="identifier">reserve</span><span class="special">(</span> <span class="identifier">max_N</span> <span class="special">);</span> 140<span class="identifier">coord_type</span> <span class="identifier">p</span><span class="special">(</span> <span class="identifier">N_start</span> <span class="special">,</span> <span class="number">0.0</span> <span class="special">);</span> 141<span class="identifier">p</span><span class="special">.</span><span class="identifier">reserve</span><span class="special">(</span> <span class="identifier">max_N</span> <span class="special">);</span> 142<span class="comment">// start with uniform momentum distribution over 20 sites</span> 143<span class="identifier">fill</span><span class="special">(</span> <span class="identifier">p</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()+</span><span class="number">20</span> <span class="special">,</span> <span class="identifier">p</span><span class="special">.</span><span class="identifier">end</span><span class="special">()-</span><span class="number">20</span> <span class="special">,</span> <span class="number">1.0</span><span class="special">/</span><span class="identifier">sqrt</span><span class="special">(</span><span class="number">20.0</span><span class="special">)</span> <span class="special">);</span> 144 145<span class="identifier">coord_type</span> <span class="identifier">distr</span><span class="special">(</span> <span class="identifier">N_start</span> <span class="special">,</span> <span class="number">0.0</span> <span class="special">);</span> 146<span class="identifier">distr</span><span class="special">.</span><span class="identifier">reserve</span><span class="special">(</span> <span class="identifier">max_N</span> <span class="special">);</span> 147 148<span class="comment">// create the system</span> 149<span class="identifier">compacton_lattice</span> <span class="identifier">lattice</span><span class="special">(</span> <span class="identifier">max_N</span> <span class="special">,</span> <span class="identifier">beta</span> <span class="special">,</span> <span class="special">(</span><span class="identifier">max_N</span><span class="special">-</span><span class="identifier">N_start</span><span class="special">)/</span><span class="number">2</span> <span class="special">);</span> 150 151<span class="comment">//create the stepper, note that we use an always_resizer because state size might change during steps</span> 152<span class="keyword">typedef</span> <span class="identifier">symplectic_rkn_sb3a_mclachlan</span><span class="special"><</span> <span class="identifier">coord_type</span> <span class="special">,</span> <span class="identifier">coord_type</span> <span class="special">,</span> <span class="keyword">double</span> <span class="special">,</span> <span class="identifier">coord_type</span> <span class="special">,</span> <span class="identifier">coord_type</span> <span class="special">,</span> <span class="keyword">double</span> <span class="special">,</span> 153 <span class="identifier">range_algebra</span> <span class="special">,</span> <span class="identifier">default_operations</span> <span class="special">,</span> <span class="identifier">always_resizer</span> <span class="special">></span> <span class="identifier">hamiltonian_stepper</span><span class="special">;</span> 154<span class="identifier">hamiltonian_stepper</span> <span class="identifier">stepper</span><span class="special">;</span> 155<span class="identifier">hamiltonian_stepper</span><span class="special">::</span><span class="identifier">state_type</span> <span class="identifier">state</span> <span class="special">=</span> <span class="identifier">make_pair</span><span class="special">(</span> <span class="identifier">q</span> <span class="special">,</span> <span class="identifier">p</span> <span class="special">);</span> 156</pre> 157<p> 158 </p> 159<p> 160 The lattice gets resized whenever the energy distribution comes close to 161 the borders <code class="computeroutput"><span class="identifier">distr</span><span class="special">[</span><span class="number">10</span><span class="special">]</span> <span class="special">></span> 162 <span class="number">1E-150</span></code>, <code class="computeroutput"><span class="identifier">distr</span><span class="special">[</span><span class="identifier">distr</span><span class="special">.</span><span class="identifier">size</span><span class="special">()-</span><span class="number">10</span><span class="special">]</span> <span class="special">></span> 163 <span class="number">1E-150</span></code>. If we increase to the left, 164 <code class="computeroutput"><span class="identifier">q</span></code> and <code class="computeroutput"><span class="identifier">p</span></code> 165 have to be rotated because their resize function always appends at the end. 166 Additionally, the start index of the potential changes in this case. 167 </p> 168<p> 169</p> 170<pre class="programlisting"><span class="keyword">double</span> <span class="identifier">t</span> <span class="special">=</span> <span class="number">0.0</span><span class="special">;</span> 171<span class="keyword">const</span> <span class="keyword">double</span> <span class="identifier">dt</span> <span class="special">=</span> <span class="number">0.1</span><span class="special">;</span> 172<span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">steps</span> <span class="special">=</span> <span class="number">10000</span><span class="special">;</span> 173<span class="keyword">for</span><span class="special">(</span> <span class="keyword">int</span> <span class="identifier">step</span> <span class="special">=</span> <span class="number">0</span> <span class="special">;</span> <span class="identifier">step</span> <span class="special"><</span> <span class="identifier">steps</span> <span class="special">;</span> <span class="special">++</span><span class="identifier">step</span> <span class="special">)</span> 174<span class="special">{</span> 175 <span class="identifier">stepper</span><span class="special">.</span><span class="identifier">do_step</span><span class="special">(</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">lattice</span><span class="special">)</span> <span class="special">,</span> <span class="identifier">state</span> <span class="special">,</span> <span class="identifier">t</span> <span class="special">,</span> <span class="identifier">dt</span> <span class="special">);</span> 176 <span class="identifier">lattice</span><span class="special">.</span><span class="identifier">energy_distribution</span><span class="special">(</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">first</span> <span class="special">,</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">second</span> <span class="special">,</span> <span class="identifier">distr</span> <span class="special">);</span> 177 <span class="keyword">if</span><span class="special">(</span> <span class="identifier">distr</span><span class="special">[</span><span class="number">10</span><span class="special">]</span> <span class="special">></span> <span class="number">1E-150</span> <span class="special">)</span> 178 <span class="special">{</span> 179 <span class="identifier">do_resize</span><span class="special">(</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">first</span> <span class="special">,</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">second</span> <span class="special">,</span> <span class="identifier">distr</span> <span class="special">,</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">first</span><span class="special">.</span><span class="identifier">size</span><span class="special">()+</span><span class="number">20</span> <span class="special">);</span> 180 <span class="identifier">rotate</span><span class="special">(</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">first</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()</span> <span class="special">,</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">first</span><span class="special">.</span><span class="identifier">end</span><span class="special">()-</span><span class="number">20</span> <span class="special">,</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">first</span><span class="special">.</span><span class="identifier">end</span><span class="special">()</span> <span class="special">);</span> 181 <span class="identifier">rotate</span><span class="special">(</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">second</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()</span> <span class="special">,</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">second</span><span class="special">.</span><span class="identifier">end</span><span class="special">()-</span><span class="number">20</span> <span class="special">,</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">second</span><span class="special">.</span><span class="identifier">end</span><span class="special">()</span> <span class="special">);</span> 182 <span class="identifier">lattice</span><span class="special">.</span><span class="identifier">change_pot_start</span><span class="special">(</span> <span class="special">-</span><span class="number">20</span> <span class="special">);</span> 183 <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">t</span> <span class="special"><<</span> <span class="string">": resized left to "</span> <span class="special"><<</span> <span class="identifier">distr</span><span class="special">.</span><span class="identifier">size</span><span class="special">()</span> <span class="special"><<</span> <span class="string">", energy = "</span> <span class="special"><<</span> <span class="identifier">lattice</span><span class="special">.</span><span class="identifier">energy</span><span class="special">(</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">first</span> <span class="special">,</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">second</span> <span class="special">)</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> 184 <span class="special">}</span> 185 <span class="keyword">if</span><span class="special">(</span> <span class="identifier">distr</span><span class="special">[</span><span class="identifier">distr</span><span class="special">.</span><span class="identifier">size</span><span class="special">()-</span><span class="number">10</span><span class="special">]</span> <span class="special">></span> <span class="number">1E-150</span> <span class="special">)</span> 186 <span class="special">{</span> 187 <span class="identifier">do_resize</span><span class="special">(</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">first</span> <span class="special">,</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">second</span> <span class="special">,</span> <span class="identifier">distr</span> <span class="special">,</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">first</span><span class="special">.</span><span class="identifier">size</span><span class="special">()+</span><span class="number">20</span> <span class="special">);</span> 188 <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">t</span> <span class="special"><<</span> <span class="string">": resized right to "</span> <span class="special"><<</span> <span class="identifier">distr</span><span class="special">.</span><span class="identifier">size</span><span class="special">()</span> <span class="special"><<</span> <span class="string">", energy = "</span> <span class="special"><<</span> <span class="identifier">lattice</span><span class="special">.</span><span class="identifier">energy</span><span class="special">(</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">first</span> <span class="special">,</span> <span class="identifier">state</span><span class="special">.</span><span class="identifier">second</span> <span class="special">)</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span> 189 <span class="special">}</span> 190 <span class="identifier">t</span> <span class="special">+=</span> <span class="identifier">dt</span><span class="special">;</span> 191<span class="special">}</span> 192</pre> 193<p> 194 </p> 195<p> 196 The <code class="computeroutput"><span class="identifier">do_resize</span></code> function simply 197 calls <code class="computeroutput"><span class="identifier">vector</span><span class="special">.</span><span class="identifier">resize</span></code> of <code class="computeroutput"><span class="identifier">q</span></code> 198 , <code class="computeroutput"><span class="identifier">p</span></code> and <code class="computeroutput"><span class="identifier">distr</span></code>. 199 </p> 200<p> 201</p> 202<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">do_resize</span><span class="special">(</span> <span class="identifier">coord_type</span> <span class="special">&</span><span class="identifier">q</span> <span class="special">,</span> <span class="identifier">coord_type</span> <span class="special">&</span><span class="identifier">p</span> <span class="special">,</span> <span class="identifier">coord_type</span> <span class="special">&</span><span class="identifier">distr</span> <span class="special">,</span> <span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">N</span> <span class="special">)</span> 203<span class="special">{</span> 204 <span class="identifier">q</span><span class="special">.</span><span class="identifier">resize</span><span class="special">(</span> <span class="identifier">N</span> <span class="special">);</span> 205 <span class="identifier">p</span><span class="special">.</span><span class="identifier">resize</span><span class="special">(</span> <span class="identifier">N</span> <span class="special">);</span> 206 <span class="identifier">distr</span><span class="special">.</span><span class="identifier">resize</span><span class="special">(</span> <span class="identifier">N</span> <span class="special">);</span> 207<span class="special">}</span> 208</pre> 209<p> 210 </p> 211<p> 212 The full example can be found in <a href="https://github.com/headmyshoulder/odeint-v2/blob/master/examples/resizing_lattice.cpp" target="_top">resizing_lattice.cpp</a> 213 </p> 214</div> 215<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 216<td align="left"></td> 217<td align="right"><div class="copyright-footer">Copyright © 2009-2015 Karsten Ahnert and Mario Mulansky<p> 218 Distributed under the Boost Software License, Version 1.0. (See accompanying 219 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>) 220 </p> 221</div></td> 222</tr></table> 223<hr> 224<div class="spirit-nav"> 225<a accesskey="p" href="using_arbitrary_precision_floating_point_types.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../tutorial.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="using_cuda__or_openmp__tbb_______via_thrust.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 226</div> 227</body> 228</html> 229
