A sample about how to compile fftw3 to library and use it in android.
Compare between different dft_2d implement efforts is shown in below table.
| Method | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | Avg(ms) |
| ffwt_plan_dft_2d | 72.54102 | 64.63599 | 55.90796 | 55.17505 | 55.146 | 56.03003 | 55.26685 | 55.08496 | 55.23608 | 55.11401 | 58.0138 |
| ffwt_plan_dft_r2c_2d | 35.82813 | 24.96289 | 24.07886 | 24.4751 | 24.16992 | 24.29199 | 23.98706 | 24.5669 | 23.98706 | 24.32202 | 25.467 |
| ffwtf_plan__dft_r2c_2d | 36.59106 | 21.4231 | 20.81299 | 17.91284 | 16.69287 | 19.25708 | 15.41089 | 15.25806 | 15.31885 | 15.29004 | 19.3968 |
| ffwtf_plan__dft_r2c_2d(neon) | 56.67188 | 4.333984 | 4.150879 | 4.089844 | 4.149902 | 4.029053 | 4.150879 | 4.943848 | 4.180908 | 5.249023 | 9.59502 |
| ffwtf_plan__dft_r2c_2d(threads=4) | 65.21582 | 29.14404 | 31.34082 | 32.07398 | 21.0271 | 22.91797 | 20.84302 | 22.15601 | 24.2002 | 33.99707 | 30.2916 |
| ffwtf_plan__dft_r2c_2d(threads=4)(neon) | 48.49316 | 16.8772 | 14.70996 | 15.47315 | 15.5332 | 16.02197 | 20.47803 | 14.43506 | 13.76318 | 13.61084 | 18.9396 |
| Test Phone | Google Nexus 4(APQ8064 1.5GHz x 4) | ||||||||||
| Test Data | Input: 160 x 160 | ||||||||||