1 #ifndef KISSFFT_CLASS_HH 2 #include <complex> 3 #include <vector> 4 5 namespace kissfft_utils { 6 7 template <typename T_scalar> 8 struct traits 9 { 10 typedef T_scalar scalar_type; 11 typedef std::complex<scalar_type> cpx_type; 12 void fill_twiddles( std::complex<T_scalar> * dst ,int nfft,bool inverse) 13 { 14 T_scalar phinc = (inverse?2:-2)* acos( (T_scalar) -1) / nfft; 15 for (int i=0;i<nfft;++i) 16 dst[i] = exp( std::complex<T_scalar>(0,i*phinc) ); 17 } 18 19 void prepare( 20 std::vector< std::complex<T_scalar> > & dst, 21 int nfft,bool inverse, 22 std::vector<int> & stageRadix, 23 std::vector<int> & stageRemainder ) 24 { 25 _twiddles.resize(nfft); 26 fill_twiddles( &_twiddles[0],nfft,inverse); 27 dst = _twiddles; 28 29 //factorize 30 //start factoring out 4's, then 2's, then 3,5,7,9,... 31 int n= nfft; 32 int p=4; 33 do { 34 while (n % p) { 35 switch (p) { 36 case 4: p = 2; break; 37 case 2: p = 3; break; 38 default: p += 2; break; 39 } 40 if (p*p>n) 41 p=n;// no more factors 42 } 43 n /= p; 44 stageRadix.push_back(p); 45 stageRemainder.push_back(n); 46 }while(n>1); 47 } 48 std::vector<cpx_type> _twiddles; 49 50 51 const cpx_type twiddle(int i) { return _twiddles[i]; } 52 }; 53 54 } 55 56 template <typename T_Scalar, 57 typename T_traits=kissfft_utils::traits<T_Scalar> 58 > 59 class kissfft 60 { 61 public: 62 typedef T_traits traits_type; 63 typedef typename traits_type::scalar_type scalar_type; 64 typedef typename traits_type::cpx_type cpx_type; 65 66 kissfft(int nfft,bool inverse,const traits_type & traits=traits_type() ) 67 :_nfft(nfft),_inverse(inverse),_traits(traits) 68 { 69 _traits.prepare(_twiddles, _nfft,_inverse ,_stageRadix, _stageRemainder); 70 } 71 72 void transform(const cpx_type * src , cpx_type * dst) 73 { 74 kf_work(0, dst, src, 1,1); 75 } 76 77 private: 78 void kf_work( int stage,cpx_type * Fout, const cpx_type * f, size_t fstride,size_t in_stride) 79 { 80 int p = _stageRadix[stage]; 81 int m = _stageRemainder[stage]; 82 cpx_type * Fout_beg = Fout; 83 cpx_type * Fout_end = Fout + p*m; 84 85 if (m==1) { 86 do{ 87 *Fout = *f; 88 f += fstride*in_stride; 89 }while(++Fout != Fout_end ); 90 }else{ 91 do{ 92 // recursive call: 93 // DFT of size m*p performed by doing 94 // p instances of smaller DFTs of size m, 95 // each one takes a decimated version of the input 96 kf_work(stage+1, Fout , f, fstride*p,in_stride); 97 f += fstride*in_stride; 98 }while( (Fout += m) != Fout_end ); 99 } 100 101 Fout=Fout_beg; 102 103 // recombine the p smaller DFTs 104 switch (p) { 105 case 2: kf_bfly2(Fout,fstride,m); break; 106 case 3: kf_bfly3(Fout,fstride,m); break; 107 case 4: kf_bfly4(Fout,fstride,m); break; 108 case 5: kf_bfly5(Fout,fstride,m); break; 109 default: kf_bfly_generic(Fout,fstride,m,p); break; 110 } 111 } 112 113 // these were #define macros in the original kiss_fft 114 void C_ADD( cpx_type & c,const cpx_type & a,const cpx_type & b) { c=a+b;} 115 void C_MUL( cpx_type & c,const cpx_type & a,const cpx_type & b) { c=a*b;} 116 void C_SUB( cpx_type & c,const cpx_type & a,const cpx_type & b) { c=a-b;} 117 void C_ADDTO( cpx_type & c,const cpx_type & a) { c+=a;} 118 void C_FIXDIV( cpx_type & ,int ) {} // NO-OP for float types 119 scalar_type S_MUL( const scalar_type & a,const scalar_type & b) { return a*b;} 120 scalar_type HALF_OF( const scalar_type & a) { return a*.5;} 121 void C_MULBYSCALAR(cpx_type & c,const scalar_type & a) {c*=a;} 122 123 void kf_bfly2( cpx_type * Fout, const size_t fstride, int m) 124 { 125 for (int k=0;k<m;++k) { 126 cpx_type t = Fout[m+k] * _traits.twiddle(k*fstride); 127 Fout[m+k] = Fout[k] - t; 128 Fout[k] += t; 129 } 130 } 131 132 void kf_bfly4( cpx_type * Fout, const size_t fstride, const size_t m) 133 { 134 cpx_type scratch[7]; 135 int negative_if_inverse = _inverse * -2 +1; 136 for (size_t k=0;k<m;++k) { 137 scratch[0] = Fout[k+m] * _traits.twiddle(k*fstride); 138 scratch[1] = Fout[k+2*m] * _traits.twiddle(k*fstride*2); 139 scratch[2] = Fout[k+3*m] * _traits.twiddle(k*fstride*3); 140 scratch[5] = Fout[k] - scratch[1]; 141 142 Fout[k] += scratch[1]; 143 scratch[3] = scratch[0] + scratch[2]; 144 scratch[4] = scratch[0] - scratch[2]; 145 scratch[4] = cpx_type( scratch[4].imag()*negative_if_inverse , -scratch[4].real()* negative_if_inverse ); 146 147 Fout[k+2*m] = Fout[k] - scratch[3]; 148 Fout[k] += scratch[3]; 149 Fout[k+m] = scratch[5] + scratch[4]; 150 Fout[k+3*m] = scratch[5] - scratch[4]; 151 } 152 } 153 154 void kf_bfly3( cpx_type * Fout, const size_t fstride, const size_t m) 155 { 156 size_t k=m; 157 const size_t m2 = 2*m; 158 cpx_type *tw1,*tw2; 159 cpx_type scratch[5]; 160 cpx_type epi3; 161 epi3 = _twiddles[fstride*m]; 162 163 tw1=tw2=&_twiddles[0]; 164 165 do{ 166 C_FIXDIV(*Fout,3); C_FIXDIV(Fout[m],3); C_FIXDIV(Fout[m2],3); 167 168 C_MUL(scratch[1],Fout[m] , *tw1); 169 C_MUL(scratch[2],Fout[m2] , *tw2); 170 171 C_ADD(scratch[3],scratch[1],scratch[2]); 172 C_SUB(scratch[0],scratch[1],scratch[2]); 173 tw1 += fstride; 174 tw2 += fstride*2; 175 176 Fout[m] = cpx_type( Fout->real() - HALF_OF(scratch[3].real() ) , Fout->imag() - HALF_OF(scratch[3].imag() ) ); 177 178 C_MULBYSCALAR( scratch[0] , epi3.imag() ); 179 180 C_ADDTO(*Fout,scratch[3]); 181 182 Fout[m2] = cpx_type( Fout[m].real() + scratch[0].imag() , Fout[m].imag() - scratch[0].real() ); 183 184 C_ADDTO( Fout[m] , cpx_type( -scratch[0].imag(),scratch[0].real() ) ); 185 ++Fout; 186 }while(--k); 187 } 188 189 void kf_bfly5( cpx_type * Fout, const size_t fstride, const size_t m) 190 { 191 cpx_type *Fout0,*Fout1,*Fout2,*Fout3,*Fout4; 192 size_t u; 193 cpx_type scratch[13]; 194 cpx_type * twiddles = &_twiddles[0]; 195 cpx_type *tw; 196 cpx_type ya,yb; 197 ya = twiddles[fstride*m]; 198 yb = twiddles[fstride*2*m]; 199 200 Fout0=Fout; 201 Fout1=Fout0+m; 202 Fout2=Fout0+2*m; 203 Fout3=Fout0+3*m; 204 Fout4=Fout0+4*m; 205 206 tw=twiddles; 207 for ( u=0; u<m; ++u ) { 208 C_FIXDIV( *Fout0,5); C_FIXDIV( *Fout1,5); C_FIXDIV( *Fout2,5); C_FIXDIV( *Fout3,5); C_FIXDIV( *Fout4,5); 209 scratch[0] = *Fout0; 210 211 C_MUL(scratch[1] ,*Fout1, tw[u*fstride]); 212 C_MUL(scratch[2] ,*Fout2, tw[2*u*fstride]); 213 C_MUL(scratch[3] ,*Fout3, tw[3*u*fstride]); 214 C_MUL(scratch[4] ,*Fout4, tw[4*u*fstride]); 215 216 C_ADD( scratch[7],scratch[1],scratch[4]); 217 C_SUB( scratch[10],scratch[1],scratch[4]); 218 C_ADD( scratch[8],scratch[2],scratch[3]); 219 C_SUB( scratch[9],scratch[2],scratch[3]); 220 221 C_ADDTO( *Fout0, scratch[7]); 222 C_ADDTO( *Fout0, scratch[8]); 223 224 scratch[5] = scratch[0] + cpx_type( 225 S_MUL(scratch[7].real(),ya.real() ) + S_MUL(scratch[8].real() ,yb.real() ), 226 S_MUL(scratch[7].imag(),ya.real()) + S_MUL(scratch[8].imag(),yb.real()) 227 ); 228 229 scratch[6] = cpx_type( 230 S_MUL(scratch[10].imag(),ya.imag()) + S_MUL(scratch[9].imag(),yb.imag()), 231 -S_MUL(scratch[10].real(),ya.imag()) - S_MUL(scratch[9].real(),yb.imag()) 232 ); 233 234 C_SUB(*Fout1,scratch[5],scratch[6]); 235 C_ADD(*Fout4,scratch[5],scratch[6]); 236 237 scratch[11] = scratch[0] + 238 cpx_type( 239 S_MUL(scratch[7].real(),yb.real()) + S_MUL(scratch[8].real(),ya.real()), 240 S_MUL(scratch[7].imag(),yb.real()) + S_MUL(scratch[8].imag(),ya.real()) 241 ); 242 243 scratch[12] = cpx_type( 244 -S_MUL(scratch[10].imag(),yb.imag()) + S_MUL(scratch[9].imag(),ya.imag()), 245 S_MUL(scratch[10].real(),yb.imag()) - S_MUL(scratch[9].real(),ya.imag()) 246 ); 247 248 C_ADD(*Fout2,scratch[11],scratch[12]); 249 C_SUB(*Fout3,scratch[11],scratch[12]); 250 251 ++Fout0;++Fout1;++Fout2;++Fout3;++Fout4; 252 } 253 } 254 255 /* perform the butterfly for one stage of a mixed radix FFT */ 256 void kf_bfly_generic( 257 cpx_type * Fout, 258 const size_t fstride, 259 int m, 260 int p 261 ) 262 { 263 int u,k,q1,q; 264 cpx_type * twiddles = &_twiddles[0]; 265 cpx_type t; 266 int Norig = _nfft; 267 cpx_type scratchbuf[p]; 268 269 for ( u=0; u<m; ++u ) { 270 k=u; 271 for ( q1=0 ; q1<p ; ++q1 ) { 272 scratchbuf[q1] = Fout[ k ]; 273 C_FIXDIV(scratchbuf[q1],p); 274 k += m; 275 } 276 277 k=u; 278 for ( q1=0 ; q1<p ; ++q1 ) { 279 int twidx=0; 280 Fout[ k ] = scratchbuf[0]; 281 for (q=1;q<p;++q ) { 282 twidx += fstride * k; 283 if (twidx>=Norig) twidx-=Norig; 284 C_MUL(t,scratchbuf[q] , twiddles[twidx] ); 285 C_ADDTO( Fout[ k ] ,t); 286 } 287 k += m; 288 } 289 } 290 } 291 292 int _nfft; 293 bool _inverse; 294 std::vector<cpx_type> _twiddles; 295 std::vector<int> _stageRadix; 296 std::vector<int> _stageRemainder; 297 traits_type _traits; 298 }; 299 #endif 300
