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- <div class="headertitle"><div class="title">GaussianElimination.h</div></div>
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- <div class="contents">
- <a href="_gaussian_elimination_8h.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a id="l00001" name="l00001"></a><span class="lineno"> 1</span><span class="comment">// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)</span></div>
- <div class="line"><a id="l00002" name="l00002"></a><span class="lineno"> 2</span><span class="comment">// SPDX-FileCopyrightText: 2021 Jorrit Rouwe</span></div>
- <div class="line"><a id="l00003" name="l00003"></a><span class="lineno"> 3</span><span class="comment">// SPDX-License-Identifier: MIT</span></div>
- <div class="line"><a id="l00004" name="l00004"></a><span class="lineno"> 4</span> </div>
- <div class="line"><a id="l00005" name="l00005"></a><span class="lineno"> 5</span><span class="preprocessor">#pragma once</span></div>
- <div class="line"><a id="l00006" name="l00006"></a><span class="lineno"> 6</span> </div>
- <div class="line"><a id="l00007" name="l00007"></a><span class="lineno"> 7</span><a class="code hl_define" href="_core_8h.html#ad14098b68b8c44ea6112601031268405">JPH_NAMESPACE_BEGIN</a></div>
- <div class="line"><a id="l00008" name="l00008"></a><span class="lineno"> 8</span> </div>
- <div class="line"><a id="l00018" name="l00018"></a><span class="lineno"> 18</span><span class="keyword">template</span> <<span class="keyword">class</span> MatrixA, <span class="keyword">class</span> MatrixB></div>
- <div class="foldopen" id="foldopen00019" data-start="{" data-end="}">
- <div class="line"><a id="l00019" name="l00019"></a><span class="lineno"><a class="line" href="_gaussian_elimination_8h.html#a292d56457a5c67858f083798c34b111c"> 19</a></span><span class="keywordtype">bool</span> <a class="code hl_function" href="_gaussian_elimination_8h.html#a292d56457a5c67858f083798c34b111c">GaussianElimination</a>(MatrixA &ioA, MatrixB &ioB, <span class="keywordtype">float</span> inTolerance = 1.0e-16f)</div>
- <div class="line"><a id="l00020" name="l00020"></a><span class="lineno"> 20</span>{</div>
- <div class="line"><a id="l00021" name="l00021"></a><span class="lineno"> 21</span> <span class="comment">// Get problem dimensions</span></div>
- <div class="line"><a id="l00022" name="l00022"></a><span class="lineno"> 22</span> <span class="keyword">const</span> <a class="code hl_typedef" href="_core_8h.html#a69aa29b598b851b0640aa225a9e5d61d">uint</a> n = ioA.GetCols();</div>
- <div class="line"><a id="l00023" name="l00023"></a><span class="lineno"> 23</span> <span class="keyword">const</span> <a class="code hl_typedef" href="_core_8h.html#a69aa29b598b851b0640aa225a9e5d61d">uint</a> m = ioB.GetCols();</div>
- <div class="line"><a id="l00024" name="l00024"></a><span class="lineno"> 24</span> </div>
- <div class="line"><a id="l00025" name="l00025"></a><span class="lineno"> 25</span> <span class="comment">// Check matrix requirement</span></div>
- <div class="line"><a id="l00026" name="l00026"></a><span class="lineno"> 26</span> <a class="code hl_define" href="_issue_reporting_8h.html#aaf6b1df827e11b7ca5f6f8778bd8f8cd">JPH_ASSERT</a>(ioA.GetRows() == n);</div>
- <div class="line"><a id="l00027" name="l00027"></a><span class="lineno"> 27</span> <a class="code hl_define" href="_issue_reporting_8h.html#aaf6b1df827e11b7ca5f6f8778bd8f8cd">JPH_ASSERT</a>(ioB.GetRows() == n);</div>
- <div class="line"><a id="l00028" name="l00028"></a><span class="lineno"> 28</span> </div>
- <div class="line"><a id="l00029" name="l00029"></a><span class="lineno"> 29</span> <span class="comment">// Create array for bookkeeping on pivoting</span></div>
- <div class="line"><a id="l00030" name="l00030"></a><span class="lineno"> 30</span> <span class="keywordtype">int</span> *ipiv = (<span class="keywordtype">int</span> *)<a class="code hl_define" href="_core_8h.html#a438e7b853f86742bcbdf0faeaa2094a2">JPH_STACK_ALLOC</a>(n * <span class="keyword">sizeof</span>(<span class="keywordtype">int</span>));</div>
- <div class="line"><a id="l00031" name="l00031"></a><span class="lineno"> 31</span> memset(ipiv, 0, n * <span class="keyword">sizeof</span>(<span class="keywordtype">int</span>));</div>
- <div class="line"><a id="l00032" name="l00032"></a><span class="lineno"> 32</span> </div>
- <div class="line"><a id="l00033" name="l00033"></a><span class="lineno"> 33</span> <span class="keywordflow">for</span> (<a class="code hl_typedef" href="_core_8h.html#a69aa29b598b851b0640aa225a9e5d61d">uint</a> i = 0; i < n; ++i)</div>
- <div class="line"><a id="l00034" name="l00034"></a><span class="lineno"> 34</span> {</div>
- <div class="line"><a id="l00035" name="l00035"></a><span class="lineno"> 35</span> <span class="comment">// Initialize pivot element as the diagonal</span></div>
- <div class="line"><a id="l00036" name="l00036"></a><span class="lineno"> 36</span> <a class="code hl_typedef" href="_core_8h.html#a69aa29b598b851b0640aa225a9e5d61d">uint</a> pivot_row = i, pivot_col = i;</div>
- <div class="line"><a id="l00037" name="l00037"></a><span class="lineno"> 37</span> </div>
- <div class="line"><a id="l00038" name="l00038"></a><span class="lineno"> 38</span> <span class="comment">// Determine pivot element</span></div>
- <div class="line"><a id="l00039" name="l00039"></a><span class="lineno"> 39</span> <span class="keywordtype">float</span> largest_element = 0.0f;</div>
- <div class="line"><a id="l00040" name="l00040"></a><span class="lineno"> 40</span> <span class="keywordflow">for</span> (<a class="code hl_typedef" href="_core_8h.html#a69aa29b598b851b0640aa225a9e5d61d">uint</a> j = 0; j < n; ++j)</div>
- <div class="line"><a id="l00041" name="l00041"></a><span class="lineno"> 41</span> <span class="keywordflow">if</span> (ipiv[j] != 1)</div>
- <div class="line"><a id="l00042" name="l00042"></a><span class="lineno"> 42</span> <span class="keywordflow">for</span> (<a class="code hl_typedef" href="_core_8h.html#a69aa29b598b851b0640aa225a9e5d61d">uint</a> k = 0; k < n; ++k)</div>
- <div class="line"><a id="l00043" name="l00043"></a><span class="lineno"> 43</span> {</div>
- <div class="line"><a id="l00044" name="l00044"></a><span class="lineno"> 44</span> <span class="keywordflow">if</span> (ipiv[k] == 0)</div>
- <div class="line"><a id="l00045" name="l00045"></a><span class="lineno"> 45</span> {</div>
- <div class="line"><a id="l00046" name="l00046"></a><span class="lineno"> 46</span> <span class="keywordtype">float</span> element = abs(ioA(j, k));</div>
- <div class="line"><a id="l00047" name="l00047"></a><span class="lineno"> 47</span> <span class="keywordflow">if</span> (element >= largest_element)</div>
- <div class="line"><a id="l00048" name="l00048"></a><span class="lineno"> 48</span> {</div>
- <div class="line"><a id="l00049" name="l00049"></a><span class="lineno"> 49</span> largest_element = element;</div>
- <div class="line"><a id="l00050" name="l00050"></a><span class="lineno"> 50</span> pivot_row = j;</div>
- <div class="line"><a id="l00051" name="l00051"></a><span class="lineno"> 51</span> pivot_col = k;</div>
- <div class="line"><a id="l00052" name="l00052"></a><span class="lineno"> 52</span> }</div>
- <div class="line"><a id="l00053" name="l00053"></a><span class="lineno"> 53</span> }</div>
- <div class="line"><a id="l00054" name="l00054"></a><span class="lineno"> 54</span> <span class="keywordflow">else</span> <span class="keywordflow">if</span> (ipiv[k] > 1)</div>
- <div class="line"><a id="l00055" name="l00055"></a><span class="lineno"> 55</span> {</div>
- <div class="line"><a id="l00056" name="l00056"></a><span class="lineno"> 56</span> <span class="keywordflow">return</span> <span class="keyword">false</span>;</div>
- <div class="line"><a id="l00057" name="l00057"></a><span class="lineno"> 57</span> }</div>
- <div class="line"><a id="l00058" name="l00058"></a><span class="lineno"> 58</span> }</div>
- <div class="line"><a id="l00059" name="l00059"></a><span class="lineno"> 59</span> </div>
- <div class="line"><a id="l00060" name="l00060"></a><span class="lineno"> 60</span> <span class="comment">// Mark this column as used</span></div>
- <div class="line"><a id="l00061" name="l00061"></a><span class="lineno"> 61</span> ++ipiv[pivot_col];</div>
- <div class="line"><a id="l00062" name="l00062"></a><span class="lineno"> 62</span> </div>
- <div class="line"><a id="l00063" name="l00063"></a><span class="lineno"> 63</span> <span class="comment">// Exchange rows when needed so that the pivot element is at ioA(pivot_col, pivot_col) instead of at ioA(pivot_row, pivot_col)</span></div>
- <div class="line"><a id="l00064" name="l00064"></a><span class="lineno"> 64</span> <span class="keywordflow">if</span> (pivot_row != pivot_col)</div>
- <div class="line"><a id="l00065" name="l00065"></a><span class="lineno"> 65</span> {</div>
- <div class="line"><a id="l00066" name="l00066"></a><span class="lineno"> 66</span> <span class="keywordflow">for</span> (<a class="code hl_typedef" href="_core_8h.html#a69aa29b598b851b0640aa225a9e5d61d">uint</a> j = 0; j < n; ++j)</div>
- <div class="line"><a id="l00067" name="l00067"></a><span class="lineno"> 67</span> std::swap(ioA(pivot_row, j), ioA(pivot_col, j));</div>
- <div class="line"><a id="l00068" name="l00068"></a><span class="lineno"> 68</span> <span class="keywordflow">for</span> (<a class="code hl_typedef" href="_core_8h.html#a69aa29b598b851b0640aa225a9e5d61d">uint</a> j = 0; j < m; ++j)</div>
- <div class="line"><a id="l00069" name="l00069"></a><span class="lineno"> 69</span> std::swap(ioB(pivot_row, j), ioB(pivot_col, j));</div>
- <div class="line"><a id="l00070" name="l00070"></a><span class="lineno"> 70</span> }</div>
- <div class="line"><a id="l00071" name="l00071"></a><span class="lineno"> 71</span> </div>
- <div class="line"><a id="l00072" name="l00072"></a><span class="lineno"> 72</span> <span class="comment">// Get diagonal element that we are about to set to 1</span></div>
- <div class="line"><a id="l00073" name="l00073"></a><span class="lineno"> 73</span> <span class="keywordtype">float</span> diagonal_element = ioA(pivot_col, pivot_col);</div>
- <div class="line"><a id="l00074" name="l00074"></a><span class="lineno"> 74</span> <span class="keywordflow">if</span> (abs(diagonal_element) < inTolerance)</div>
- <div class="line"><a id="l00075" name="l00075"></a><span class="lineno"> 75</span> <span class="keywordflow">return</span> <span class="keyword">false</span>;</div>
- <div class="line"><a id="l00076" name="l00076"></a><span class="lineno"> 76</span> </div>
- <div class="line"><a id="l00077" name="l00077"></a><span class="lineno"> 77</span> <span class="comment">// Divide the whole row by the pivot element, making ioA(pivot_col, pivot_col) = 1</span></div>
- <div class="line"><a id="l00078" name="l00078"></a><span class="lineno"> 78</span> <span class="keywordflow">for</span> (<a class="code hl_typedef" href="_core_8h.html#a69aa29b598b851b0640aa225a9e5d61d">uint</a> j = 0; j < n; ++j)</div>
- <div class="line"><a id="l00079" name="l00079"></a><span class="lineno"> 79</span> ioA(pivot_col, j) /= diagonal_element;</div>
- <div class="line"><a id="l00080" name="l00080"></a><span class="lineno"> 80</span> <span class="keywordflow">for</span> (<a class="code hl_typedef" href="_core_8h.html#a69aa29b598b851b0640aa225a9e5d61d">uint</a> j = 0; j < m; ++j)</div>
- <div class="line"><a id="l00081" name="l00081"></a><span class="lineno"> 81</span> ioB(pivot_col, j) /= diagonal_element;</div>
- <div class="line"><a id="l00082" name="l00082"></a><span class="lineno"> 82</span> ioA(pivot_col, pivot_col) = 1.0f;</div>
- <div class="line"><a id="l00083" name="l00083"></a><span class="lineno"> 83</span> </div>
- <div class="line"><a id="l00084" name="l00084"></a><span class="lineno"> 84</span> <span class="comment">// Next reduce the rows, except for the pivot one,</span></div>
- <div class="line"><a id="l00085" name="l00085"></a><span class="lineno"> 85</span> <span class="comment">// after this step the pivot_col column is zero except for the pivot element which is 1</span></div>
- <div class="line"><a id="l00086" name="l00086"></a><span class="lineno"> 86</span> <span class="keywordflow">for</span> (<a class="code hl_typedef" href="_core_8h.html#a69aa29b598b851b0640aa225a9e5d61d">uint</a> j = 0; j < n; ++j)</div>
- <div class="line"><a id="l00087" name="l00087"></a><span class="lineno"> 87</span> <span class="keywordflow">if</span> (j != pivot_col)</div>
- <div class="line"><a id="l00088" name="l00088"></a><span class="lineno"> 88</span> {</div>
- <div class="line"><a id="l00089" name="l00089"></a><span class="lineno"> 89</span> <span class="keywordtype">float</span> element = ioA(j, pivot_col);</div>
- <div class="line"><a id="l00090" name="l00090"></a><span class="lineno"> 90</span> <span class="keywordflow">for</span> (<a class="code hl_typedef" href="_core_8h.html#a69aa29b598b851b0640aa225a9e5d61d">uint</a> k = 0; k < n; ++k)</div>
- <div class="line"><a id="l00091" name="l00091"></a><span class="lineno"> 91</span> ioA(j, k) -= ioA(pivot_col, k) * element;</div>
- <div class="line"><a id="l00092" name="l00092"></a><span class="lineno"> 92</span> <span class="keywordflow">for</span> (<a class="code hl_typedef" href="_core_8h.html#a69aa29b598b851b0640aa225a9e5d61d">uint</a> k = 0; k < m; ++k)</div>
- <div class="line"><a id="l00093" name="l00093"></a><span class="lineno"> 93</span> ioB(j, k) -= ioB(pivot_col, k) * element;</div>
- <div class="line"><a id="l00094" name="l00094"></a><span class="lineno"> 94</span> ioA(j, pivot_col) = 0.0f;</div>
- <div class="line"><a id="l00095" name="l00095"></a><span class="lineno"> 95</span> }</div>
- <div class="line"><a id="l00096" name="l00096"></a><span class="lineno"> 96</span> }</div>
- <div class="line"><a id="l00097" name="l00097"></a><span class="lineno"> 97</span> </div>
- <div class="line"><a id="l00098" name="l00098"></a><span class="lineno"> 98</span> <span class="comment">// Success</span></div>
- <div class="line"><a id="l00099" name="l00099"></a><span class="lineno"> 99</span> <span class="keywordflow">return</span> <span class="keyword">true</span>;</div>
- <div class="line"><a id="l00100" name="l00100"></a><span class="lineno"> 100</span>}</div>
- </div>
- <div class="line"><a id="l00101" name="l00101"></a><span class="lineno"> 101</span> </div>
- <div class="line"><a id="l00102" name="l00102"></a><span class="lineno"> 102</span><a class="code hl_define" href="_core_8h.html#a73da8725998b00321a9db341202d650d">JPH_NAMESPACE_END</a></div>
- <div class="ttc" id="a_core_8h_html_a438e7b853f86742bcbdf0faeaa2094a2"><div class="ttname"><a href="_core_8h.html#a438e7b853f86742bcbdf0faeaa2094a2">JPH_STACK_ALLOC</a></div><div class="ttdeci">#define JPH_STACK_ALLOC(n)</div><div class="ttdef"><b>Definition</b> Core.h:558</div></div>
- <div class="ttc" id="a_core_8h_html_a69aa29b598b851b0640aa225a9e5d61d"><div class="ttname"><a href="_core_8h.html#a69aa29b598b851b0640aa225a9e5d61d">uint</a></div><div class="ttdeci">unsigned int uint</div><div class="ttdef"><b>Definition</b> Core.h:500</div></div>
- <div class="ttc" id="a_core_8h_html_a73da8725998b00321a9db341202d650d"><div class="ttname"><a href="_core_8h.html#a73da8725998b00321a9db341202d650d">JPH_NAMESPACE_END</a></div><div class="ttdeci">#define JPH_NAMESPACE_END</div><div class="ttdef"><b>Definition</b> Core.h:425</div></div>
- <div class="ttc" id="a_core_8h_html_ad14098b68b8c44ea6112601031268405"><div class="ttname"><a href="_core_8h.html#ad14098b68b8c44ea6112601031268405">JPH_NAMESPACE_BEGIN</a></div><div class="ttdeci">#define JPH_NAMESPACE_BEGIN</div><div class="ttdef"><b>Definition</b> Core.h:419</div></div>
- <div class="ttc" id="a_gaussian_elimination_8h_html_a292d56457a5c67858f083798c34b111c"><div class="ttname"><a href="_gaussian_elimination_8h.html#a292d56457a5c67858f083798c34b111c">GaussianElimination</a></div><div class="ttdeci">JPH_NAMESPACE_BEGIN bool GaussianElimination(MatrixA &ioA, MatrixB &ioB, float inTolerance=1.0e-16f)</div><div class="ttdef"><b>Definition</b> GaussianElimination.h:19</div></div>
- <div class="ttc" id="a_issue_reporting_8h_html_aaf6b1df827e11b7ca5f6f8778bd8f8cd"><div class="ttname"><a href="_issue_reporting_8h.html#aaf6b1df827e11b7ca5f6f8778bd8f8cd">JPH_ASSERT</a></div><div class="ttdeci">#define JPH_ASSERT(...)</div><div class="ttdef"><b>Definition</b> IssueReporting.h:33</div></div>
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