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1 | // Created on: 2005-12-19 |
2 | // Created by: Julia GERASIMOVA |
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3 | // Copyright (c) 2005-2014 OPEN CASCADE SAS |
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4 | // |
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5 | // This file is part of Open CASCADE Technology software library. |
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6 | // |
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7 | // This library is free software; you can redistribute it and/or modify it under |
8 | // the terms of the GNU Lesser General Public License version 2.1 as published |
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9 | // by the Free Software Foundation, with special exception defined in the file |
10 | // OCCT_LGPL_EXCEPTION.txt. Consult the file LICENSE_LGPL_21.txt included in OCCT |
11 | // distribution for complete text of the license and disclaimer of any warranty. |
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12 | // |
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13 | // Alternatively, this file may be used under the terms of Open CASCADE |
14 | // commercial license or contractual agreement. |
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15 | |
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16 | |
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17 | #include <math_Array1OfValueAndWeight.hxx> |
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18 | #include <math_ComputeGaussPointsAndWeights.hxx> |
19 | #include <math_EigenValuesSearcher.hxx> |
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20 | #include <Standard_ErrorHandler.hxx> |
21 | |
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22 | #include <algorithm> |
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23 | math_ComputeGaussPointsAndWeights::math_ComputeGaussPointsAndWeights(const Standard_Integer Number) |
24 | { |
25 | myIsDone = Standard_False; |
26 | |
27 | try { |
28 | myPoints = new TColStd_HArray1OfReal(1, Number); |
29 | myWeights = new TColStd_HArray1OfReal(1, Number); |
30 | |
31 | Standard_Integer i; |
32 | |
33 | TColStd_Array1OfReal aDiag(1, Number); |
34 | TColStd_Array1OfReal aSubDiag(1, Number); |
35 | |
36 | //Initialization of a real symmetric tridiagonal matrix for |
37 | //computation of Gauss quadrature. |
38 | |
39 | for (i = 1; i <= Number; i++) { |
40 | aDiag(i) = 0.; |
41 | |
42 | if (i == 1) |
43 | aSubDiag(i) = 0.; |
44 | else { |
45 | Standard_Integer sqrIm1 = (i-1)*(i-1); |
46 | aSubDiag(i) = sqrIm1/(4.*sqrIm1 - 1); |
47 | aSubDiag(i) = Sqrt(aSubDiag(i)); |
48 | } |
49 | } |
50 | |
51 | // Compute eigen values. |
52 | math_EigenValuesSearcher EVsearch(aDiag, aSubDiag); |
53 | |
54 | if (EVsearch.IsDone()) { |
55 | math_Array1OfValueAndWeight VWarray(1, Number); |
56 | for (i = 1; i <= Number; i++) { |
57 | math_Vector anEigenVector = EVsearch.EigenVector(i); |
58 | Standard_Real aWeight = anEigenVector(1); |
59 | aWeight = 2. * aWeight * aWeight; |
60 | math_ValueAndWeight EVW( EVsearch.EigenValue(i), aWeight ); |
61 | VWarray(i) = EVW; |
62 | } |
63 | |
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64 | std::sort (VWarray.begin(), VWarray.end()); |
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65 | |
66 | for (i = 1; i <= Number; i++) { |
67 | myPoints->ChangeValue(i) = VWarray(i).Value(); |
68 | myWeights->ChangeValue(i) = VWarray(i).Weight(); |
69 | } |
70 | myIsDone = Standard_True; |
71 | } |
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72 | } catch (Standard_Failure const&) { |
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73 | } |
74 | } |
75 | |
76 | Standard_Boolean math_ComputeGaussPointsAndWeights::IsDone() const |
77 | { |
78 | return myIsDone; |
79 | } |
80 | |
81 | math_Vector math_ComputeGaussPointsAndWeights::Points() const |
82 | { |
83 | Standard_Integer Number = myPoints->Length(); |
84 | math_Vector thePoints(1, Number); |
85 | for (Standard_Integer i = 1; i <= Number; i++) |
86 | thePoints(i) = myPoints->Value(i); |
87 | |
88 | return thePoints; |
89 | } |
90 | |
91 | math_Vector math_ComputeGaussPointsAndWeights::Weights() const |
92 | { |
93 | Standard_Integer Number = myWeights->Length(); |
94 | math_Vector theWeights(1, Number); |
95 | for (Standard_Integer i = 1; i <= Number; i++) |
96 | theWeights(i) = myWeights->Value(i); |
97 | |
98 | return theWeights; |
99 | } |