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prune.cpp
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#include "fft.h"
using namespace std;
template <int N, int S, int SO = 1, typename T=float>
struct prunefft {
typedef complex<T> cfloat_t;
prunefft<N/2, S*2, SO> s2;
prunefft<N/4, S*4, SO> s4;
void apply(const cfloat_t *in, cfloat_t *out, const cfloat_t *l1, const cfloat_t *l3, unsigned log2stride) {
constexpr cfloat_t I(0.0f, 1.0f);
s2.apply(in, out, l1, l3, log2stride + 1);
s4.apply(in + S, out + N/2*SO, l1, l3, log2stride + 2);
s4.apply(in + 3*S, out + 3*N/4*SO, l1, l3, log2stride + 2);
{
cfloat_t Uk = out[0];
cfloat_t Zk = out[0+SO*N/2];
cfloat_t Uk2 = out[0+SO*N/4];
cfloat_t Zdk = out[0+SO*3*N/4];
out[0] = Uk + (Zk + Zdk);
out[0+SO*N/2] = Uk - (Zk + Zdk);
out[0+SO*N/4] = Uk2 - I*(Zk - Zdk);
out[0+SO*3*N/4] = Uk2 + I*(Zk - Zdk);
}
for(unsigned k = 1; k < N/4; ++k) {
cfloat_t Uk = out[SO*(k)];
cfloat_t Zk = out[SO*(k+N/2)];
cfloat_t Uk2 = out[SO*(k+N/4)];
cfloat_t Zdk = out[SO*(k+3*N/4)];
cfloat_t w1 = l1[k << log2stride];
cfloat_t w3 = l3[k << log2stride];
out[SO*(k)] = Uk + (w1*Zk + w3*Zdk);
out[SO*(k+N/2)] = Uk - (w1*Zk + w3*Zdk);
out[SO*(k+N/4)] = Uk2 - I*(w1*Zk - w3*Zdk);
out[SO*(k+3*N/4)] = Uk2 + I*(w1*Zk - w3*Zdk);
}
}
};
template <int S, int SO, typename T>
struct prunefft<4, S, SO, T> {
typedef complex<T> cfloat_t;
void apply(const cfloat_t *in, cfloat_t *out, const cfloat_t *l1, const cfloat_t *l3, unsigned log2stride) {
(void)l1;
(void)l3;
(void)log2stride;
cfloat_t Uk = in[0];
out[0] = Uk;
out[SO*2] = Uk;
out[SO] = Uk;
out[SO*3] = Uk;
}
};
template <int S, int SO, typename T>
struct prunefft<8, S, SO, T> {
typedef complex<T> cfloat_t;
void apply(const cfloat_t *in, cfloat_t *out, const cfloat_t *l1, const cfloat_t *l3, unsigned log2stride) {
(void)l1;
(void)l3;
(void)log2stride;
{
cfloat_t Uk = in[0];
out[SO*0] = Uk;
out[SO*1] = Uk;
out[SO*2] = Uk;
out[SO*3] = Uk;
out[SO*4] = Uk;
out[SO*5] = Uk;
out[SO*6] = Uk;
out[SO*7] = Uk;
}
}
};
template <int S, int SO, typename T>
struct prunefft<16, S, SO, T> {
typedef complex<T> cfloat_t;
void apply(const cfloat_t *in, cfloat_t *out, const cfloat_t *l1, const cfloat_t *l3, unsigned log2stride) {
(void)l1;
(void)l3;
(void)log2stride;
{
cfloat_t Uk = in[0];
out[SO*0] = Uk;
out[SO*1] = Uk;
out[SO*2] = Uk;
out[SO*3] = Uk;
out[SO*4] = Uk;
out[SO*5] = Uk;
out[SO*6] = Uk;
out[SO*7] = Uk;
out[SO*8] = Uk;
out[SO*9] = Uk;
out[SO*10] = Uk;
out[SO*11] = Uk;
out[SO*12] = Uk;
out[SO*13] = Uk;
out[SO*14] = Uk;
out[SO*15] = Uk;
}
}
};
template <int S, int SO, typename T>
struct prunefft<32, S, SO, T> {
typedef complex<T> cfloat_t;
void apply(const cfloat_t *in, cfloat_t *out, const cfloat_t *l1, const cfloat_t *l3, unsigned log2stride) {
(void)l1;
(void)l3;
(void)log2stride;
{
cfloat_t Uk = in[0];
out[SO*0] = Uk;
out[SO*1] = Uk;
out[SO*2] = Uk;
out[SO*3] = Uk;
out[SO*4] = Uk;
out[SO*5] = Uk;
out[SO*6] = Uk;
out[SO*7] = Uk;
out[SO*8] = Uk;
out[SO*9] = Uk;
out[SO*10] = Uk;
out[SO*11] = Uk;
out[SO*12] = Uk;
out[SO*13] = Uk;
out[SO*14] = Uk;
out[SO*15] = Uk;
out[SO*16] = Uk;
out[SO*17] = Uk;
out[SO*18] = Uk;
out[SO*19] = Uk;
out[SO*20] = Uk;
out[SO*21] = Uk;
out[SO*22] = Uk;
out[SO*23] = Uk;
out[SO*24] = Uk;
out[SO*25] = Uk;
out[SO*26] = Uk;
out[SO*27] = Uk;
out[SO*28] = Uk;
out[SO*29] = Uk;
out[SO*30] = Uk;
out[SO*31] = Uk;
}
}
};
int main()
{
complex<float> m[1024];
complex<float> out[1024];
complex<float> out2[1024];
for (int i = 0; i != 16; ++i) {
//m[i] = {float(i+1000), float(2*i+100)};
m[1023-i] = float(i+2000);
}
const lut<256, 1> l1;
const lut<256, 3> l3;
splitfft<1024, 1, 1> sfft;
prunefft<1024, 1, 1> pfft;
sfft.apply(m, out, l1.d, l3.d, 0);
pfft.apply(m, out2, l1.d, l3.d, 0);
//printf("%f,%f\n", static_cast<double>(cshift), static_cast<double>(rshift));
for (int i = 0; i != 1024; ++i) {
if (abs(out[i]-out2[i]) > 1e-7)
printf("prune failed at %d!\n", i);
}
return 0;
}