| /* |
| * Copyright (c) 2019 ARM Limited. |
| * |
| * SPDX-License-Identifier: MIT |
| * |
| * Permission is hereby granted, free of charge, to any person obtaining a copy |
| * of this software and associated documentation files (the "Software"), to |
| * deal in the Software without restriction, including without limitation the |
| * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or |
| * sell copies of the Software, and to permit persons to whom the Software is |
| * furnished to do so, subject to the following conditions: |
| * |
| * The above copyright notice and this permission notice shall be included in all |
| * copies or substantial portions of the Software. |
| * |
| * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE |
| * SOFTWARE. |
| */ |
| #include "arm_compute/core/utils/helpers/fft.h" |
| |
| #include <numeric> |
| |
| namespace arm_compute |
| { |
| namespace helpers |
| { |
| namespace fft |
| { |
| std::vector<unsigned int> decompose_stages(unsigned int N, const std::set<unsigned int> &supported_factors) |
| { |
| std::vector<unsigned int> stages; |
| unsigned int res = N; |
| |
| // Early exit if no supported factors are provided |
| if(supported_factors.empty()) |
| { |
| return stages; |
| } |
| |
| // Create reverse iterator (Start decomposing from the larger supported factors) |
| auto rfactor_it = supported_factors.rbegin(); |
| |
| // Decomposition step |
| while(res != 0) |
| { |
| const unsigned int factor = *rfactor_it; |
| if(0 == (res % factor) && res >= factor) |
| { |
| stages.push_back(factor); |
| res /= factor; |
| } |
| else |
| { |
| ++rfactor_it; |
| if(rfactor_it == supported_factors.rend()) |
| { |
| if(res > 1) |
| { |
| // Couldn't decompose with given factors |
| stages.clear(); |
| return stages; |
| } |
| else |
| { |
| res = 0; |
| } |
| } |
| } |
| } |
| |
| return stages; |
| } |
| |
| std::vector<unsigned int> digit_reverse_indices(unsigned int N, const std::vector<unsigned int> &fft_stages) |
| { |
| std::vector<unsigned int> idx_digit_reverse; |
| |
| // Early exit in case N and fft stages do not match |
| const float stages_prod = std::accumulate(std::begin(fft_stages), std::end(fft_stages), 1, std::multiplies<unsigned int>()); |
| if(stages_prod != N) |
| { |
| return idx_digit_reverse; |
| } |
| |
| // Resize digit reverse vector |
| idx_digit_reverse.resize(N); |
| |
| // Get number of radix stages |
| unsigned int n_stages = fft_stages.size(); |
| |
| // Scan elements |
| for(unsigned int n = 0; n < N; ++n) |
| { |
| unsigned int k = n; |
| unsigned int Nx = fft_stages[0]; |
| |
| // Scan stages |
| for(unsigned int s = 1; s < n_stages; ++s) |
| { |
| // radix of stage i-th |
| unsigned int Ny = fft_stages[s]; |
| unsigned int Ni = Ny * Nx; |
| |
| // Update k index |
| k = (k * Ny) % Ni + (k / Nx) % Ny + Ni * (k / Ni); |
| |
| // Update Nx |
| Nx *= Ny; |
| } |
| |
| // K is the index of digit-reverse |
| idx_digit_reverse[n] = k; |
| } |
| |
| return idx_digit_reverse; |
| } |
| } // namespace fft |
| } // namespace helpers |
| } // namespace arm_compute |