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#include "patterns.h"
void permute_addr(int N, int offset, int stride, int *d) {
int i, a[4] = {0,2,1,3};
for(i=0;i<4;i++) {
d[i] = offset + (a[i] << stride);
if(d[i] < 0) d[i] += N;
}
}
void ffts_hardcodedleaf_is_rec(ptrdiff_t **is, int bigN, int N, int poffset, int offset, int stride, int even, int VL) {
if(N > 4) {
ffts_hardcodedleaf_is_rec(is, bigN, N/2, poffset, offset, stride + 1, even, VL);
if(N/4 >= 4) ffts_hardcodedleaf_is_rec(is, bigN, N/4, poffset+(1<<stride),offset+(N/2), stride + 2, 0, VL);
if(N/4 >= 4) ffts_hardcodedleaf_is_rec(is, bigN, N/4, poffset-(1<<stride),offset+(3*N/4), stride + 2, 0, VL);
else {
int temp = poffset+(1<<stride);
if(temp < 0) temp += bigN;
temp *= 2;
if(!(temp % (VL*2))) {
(*is)[0] = poffset+(1<<stride);
(*is)[1] = poffset+(1<<stride)+(1<<(stride+2));
(*is)[2] = poffset-(1<<stride);
(*is)[3] = poffset-(1<<stride)+(1<<(stride+2));
int i;
for(i=0;i<4;i++) if((*is)[i] < 0) (*is)[i] += bigN;
for(i=0;i<4;i++) (*is)[i] *= 2;
*is += 4;
}
}
}else if(N == 4) {
int perm[4];
permute_addr(bigN, poffset, stride, perm);
if(!((perm[0]*2) % (VL*2))) {
int i;
for(i=0;i<4;i++) {
(*is)[i] = perm[i] * 2;
}
*is += 4;
}
}
}
void ffts_init_is(ffts_plan_t *p, int N, int leafN, int VL) {
int i, i0 = N/leafN/3+1, i1=N/leafN/3, i2 = N/leafN/3;
int stride = log(N/leafN)/log(2);
p->is = malloc(N/VL * sizeof(ptrdiff_t));
ptrdiff_t *is = p->is;
if((N/leafN) % 3 > 1) i1++;
for(i=0;i<i0;i++) ffts_hardcodedleaf_is_rec(&is, N, leafN, i, 0, stride, 1, VL);
for(i=i0;i<i0+i1;i++) {
ffts_hardcodedleaf_is_rec(&is, N, leafN/2, i, 0, stride+1, 1, VL);
ffts_hardcodedleaf_is_rec(&is, N, leafN/2, i-(1<<stride), 0, stride+1, 1, VL);
}
for(i=0-i2;i<0;i++) ffts_hardcodedleaf_is_rec(&is, N, leafN, i, 0, stride, 1, VL);
//for(i=0;i<N/VL;i++) {
// printf("%td ", p->is[i]);
// if(i % 16 == 15) printf("\n");
//}
p->i0 = i0; p->i1 = i1;
}
void ffts_elaborate_offsets(ptrdiff_t *offsets, int leafN, int N, int ioffset, int ooffset, int stride, int even) {
if((even && N == leafN) || (!even && N <= leafN)) {
offsets[2*(ooffset/leafN)] = ioffset*2;
offsets[2*(ooffset/leafN)+1] = ooffset;
}else if(N > 4) {
ffts_elaborate_offsets(offsets, leafN, N/2, ioffset, ooffset, stride+1, even);
ffts_elaborate_offsets(offsets, leafN, N/4, ioffset+(1<<stride), ooffset+N/2, stride+2, 0);
if(N/4 >= leafN)
ffts_elaborate_offsets(offsets, leafN, N/4, ioffset-(1<<stride), ooffset+3*N/4, stride+2, 0);
}
}
int compare_offsets(const void *a, const void *b) {
return ((ptrdiff_t *)a)[0] - ((ptrdiff_t *)b)[0];
}
uint32_t reverse_bits(uint32_t a, int n) {
uint32_t x = 0;
int i;
for(i=0;i<n;i++) {
if(a & (1 << i)) x |= 1 << (n-i-1);
}
return x;
}
void ffts_init_offsets(ffts_plan_t *p, int N, int leafN) {
ptrdiff_t *offsets = malloc(2 * N/leafN * sizeof(ptrdiff_t));
ffts_elaborate_offsets(offsets, leafN, N, 0, 0, 1, 1);
size_t i;
for(i=0;i<2*N/leafN;i+=2) {
if(offsets[i] < 0) offsets[i] = N + offsets[i];
}
qsort(offsets, N/leafN, 2 * sizeof(ptrdiff_t), compare_offsets);
//elaborate_is(p, N, 0, 0, 1);
p->offsets = malloc(N/leafN * sizeof(ptrdiff_t));
for(i=0;i<N/leafN;i++) {
p->offsets[i] = offsets[i*2+1]*2;
}
//for(i=0;i<N/leafN;i++) {
// printf("%4d %4d\n", p->offsets[i], reverse_bits(p->offsets[i], __builtin_ctzl(2*N)));
//}
free(offsets);
}
/*
int tree_count(int N, int leafN, int offset) {
if(N <= leafN) return 0;
int count = 0;
count += tree_count(N/4, leafN, offset);
count += tree_count(N/8, leafN, offset + N/4);
count += tree_count(N/8, leafN, offset + N/4 + N/8);
count += tree_count(N/4, leafN, offset + N/2);
count += tree_count(N/4, leafN, offset + 3*N/4);
return 1 + count;
}
void elaborate_tree(transform_index_t **p, int N, int leafN, int offset) {
if(N <= leafN) return;
elaborate_tree(p, N/4, leafN, offset);
elaborate_tree(p, N/8, leafN, offset + N/4);
elaborate_tree(p, N/8, leafN, offset + N/4 + N/8);
elaborate_tree(p, N/4, leafN, offset + N/2);
elaborate_tree(p, N/4, leafN, offset + 3*N/4);
(*p)[0] = N;
(*p)[1] = offset*2;
(*p)+=2;
}
void ffts_init_tree(ffts_plan_t *p, int N, int leafN) {
int count = tree_count(N, leafN, 0) + 1;
transform_index_t *ps = p->transforms = malloc(count * 2 * sizeof(transform_index_t));
//printf("count = %d\n", count);
elaborate_tree(&ps, N, leafN, 0);
#ifdef __ARM_NEON__
ps -= 2;
#endif
ps[0] = 0;
ps[1] = 0;
//int i;
//for(i=0;i<count;i++) {
// fprintf(stderr, "%lu %lu - %d\n", p->transforms[i*2], p->transforms[i*2+1],
// __builtin_ctzl(p->transforms[i*2]) - 5);
//}
}
*/
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