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https://github.com/NGSolve/netgen.git
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112 lines
2.2 KiB
C++
112 lines
2.2 KiB
C++
#include <mystdlib.h>
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#include <myadt.hpp>
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#include <gprim.hpp>
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namespace netgen
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{
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/*
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// template <>
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inline void CalcInverse (const Mat<2,2> & m, Mat<2,2> & inv)
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{
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double det = m(0,0) * m(1,1) - m(0,1) * m(1,0);
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if (det == 0)
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{
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inv = 0;
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return;
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}
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double idet = 1.0 / det;
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inv(0,0) = idet * m(1,1);
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inv(0,1) = -idet * m(0,1);
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inv(1,0) = -idet * m(1,0);
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inv(1,1) = idet * m(0,0);
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}
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*/
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// template <>
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void CalcInverse (const Mat<3,3> & m, Mat<3,3> & inv)
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{
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double det = Det (m);
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if (det == 0)
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{
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inv = 0;
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return;
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}
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double idet = 1.0 / det;
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inv(0,0) = idet * (m(1,1) * m(2,2) - m(1,2) * m(2,1));
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inv(1,0) = -idet * (m(1,0) * m(2,2) - m(1,2) * m(2,0));
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inv(2,0) = idet * (m(1,0) * m(2,1) - m(1,1) * m(2,0));
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inv(0,1) = -idet * (m(0,1) * m(2,2) - m(0,2) * m(2,1));
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inv(1,1) = idet * (m(0,0) * m(2,2) - m(0,2) * m(2,0));
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inv(2,1) = -idet * (m(0,0) * m(2,1) - m(0,1) * m(2,0));
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inv(0,2) = idet * (m(0,1) * m(1,2) - m(0,2) * m(1,1));
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inv(1,2) = -idet * (m(0,0) * m(1,2) - m(0,2) * m(1,0));
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inv(2,2) = idet * (m(0,0) * m(1,1) - m(0,1) * m(1,0));
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}
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/*
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// template <>
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void CalcInverse (const Mat<2,3> & m, Mat<3,2> & inv)
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{
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Mat<2,2> a = m * Trans (m);
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Mat<2,2> ainv;
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CalcInverse (a, ainv);
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inv = Trans (m) * ainv;
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}
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*/
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double Det (const Mat<2,2> & m)
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{
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return m(0,0) * m(1,1) - m(0,1) * m(1,0);
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}
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double Det (const Mat<3,3> & m)
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{
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return
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m(0,0) * m(1,1) * m(2,2)
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+ m(1,0) * m(2,1) * m(0,2)
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+ m(2,0) * m(0,1) * m(1,2)
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- m(0,0) * m(2,1) * m(1,2)
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- m(1,0) * m(0,1) * m(2,2)
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- m(2,0) * m(1,1) * m(0,2);
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}
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void EigenValues (const Mat<3,3> & m, Vec<3> & ev)
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{
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const double pi = 3.141592;
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double a, b, c, d;
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double p, q;
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double arg;
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a = -1.;
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b = m(0,0) + m(1,1) + m(2,2);
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c = -( m(0,0)*m(2,2) + m(1,1)*m(2,2) + m(0,0)*m(1,1) - sqr(m(0,1)) - sqr(m(0,2)) - sqr(m(1,2)) );
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d = Det (m);
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p = 3.*a*c - sqr(b);
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q = 27.*sqr(a)*d - 9.*a*b*c + 2.*sqr(b)*b;
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arg = acos((-q/2)/sqrt(-(p*p*p)));
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ev(0) = (2. * sqrt(-p) * cos(arg/3.) - b) / 3.*a;
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ev(1) = (-2. * sqrt(-p) * cos(arg/3.+pi/3) - b) / 3.*a;
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ev(2) = (-2. * sqrt(-p) * cos(arg/3.-pi/3)- b) / 3.*a;
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}
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}
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