Rev Author Line No. Line
178 kaklik 1 #include <fftw3.h>
2 #include <boost/array.hpp>
3  
4 namespace mimas {
5  
6 // Helping function-object for fft and invfft.
7 template< typename Real >
8 struct dft_
9 {
10 void operator()( int rank, const int *n, const std::complex< Real > *in,
11 std::complex< Real > *out, int sign );
12 };
13  
14 template< typename Real, std::size_t Dim, typename TPtr >
15 boost::multi_array< std::complex< Real >, Dim > fft_t< Real, Dim, TPtr >::operator()
16 ( const boost::const_multi_array_ref< std::complex< Real >, Dim, TPtr > &field )
17 {
18 boost::array< int, Dim > shape;
19 std::copy( field.shape(), field.shape() + Dim, shape.begin() );
20  
21 boost::multi_array< std::complex< Real >, Dim > retVal( shape );
22  
23 dft_< Real > dft;
24 dft( Dim, shape.begin(), field.data(), retVal.data(), -1 );
25  
26 return retVal;
27 }
28  
29 template< typename Real, std::size_t Dim, typename TPtr >
30 boost::multi_array< std::complex< Real >, Dim > invfft_t< Real, Dim, TPtr >::operator()
31 ( const boost::const_multi_array_ref< std::complex< Real >, Dim, TPtr > &field )
32 {
33 boost::array< int, Dim > shape;
34 std::copy( field.shape(), field.shape() + Dim, shape.begin() );
35  
36 boost::multi_array< std::complex< Real >, Dim > retVal( shape );
37  
38 dft_< Real > dft;
39 dft( Dim, shape.begin(), field.data(), retVal.data(), +1 );
40  
41 return retVal * std::complex< Real >( 1.0 / retVal.num_elements() );
42 }
43  
44 // Helping function-object for rfft.
45 template< typename Real >
46 struct dft_r2c_
47 {
48 void operator()( int rank, const int *n, const Real *in,
49 std::complex< Real > *out );
50 };
51  
52 template< typename Real, std::size_t Dim, typename TPtr >
53 boost::multi_array< std::complex< Real >, Dim > rfft_t< Real, Dim, TPtr >::operator()
54 ( const boost::const_multi_array_ref< Real, Dim, TPtr > &field )
55 {
56 assert( field.shape()[ Dim - 1 ] % 2 == 0 );
57  
58 boost::array< int, Dim > shape1, shape2;
59 std::copy( field.shape(), field.shape() + Dim, shape1.begin() );
60 std::copy( field.shape(), field.shape() + Dim, shape2.begin() );
61 shape1[ Dim - 1 ] = shape1[ Dim - 1 ] / 2 + 1;
62  
63 boost::multi_array< std::complex< Real >, Dim > retVal( shape1 );
64  
65 dft_r2c_< Real > dft_r2c;
66 dft_r2c( Dim, shape2.begin(), field.data(), retVal.data() );
67  
68 return retVal;
69 }
70  
71 // Helping function-object for invrfft.
72 template< typename Real >
73 struct dft_c2r_
74 {
75 void operator()( int rank, const int *n, const std::complex< Real > *in,
76 Real *out );
77 };
78  
79 template< typename Real, std::size_t Dim, typename TPtr >
80 boost::multi_array< Real, Dim > invrfft_t< Real, Dim, TPtr >::operator()
81 ( const boost::const_multi_array_ref< std::complex< Real >, Dim, TPtr > &field )
82 {
83 // Doesn't preserve input.
84 boost::multi_array< std::complex< Real >, Dim > copy( field );
85  
86 boost::array< int, Dim > shape;
87 std::copy( field.shape(), field.shape() + Dim, shape.begin() );
88 shape[ Dim - 1 ] = ( shape[ Dim - 1 ] - 1 ) * 2;
89  
90 boost::multi_array< Real, Dim > retVal( shape );
91  
92 dft_c2r_< Real > dft_c2r;
93 dft_c2r( Dim, shape.begin(), copy.data(), retVal.data() );
94  
95 return retVal * (Real)( 1.0 / retVal.num_elements() );
96 }
97  
98 }