The "cost" is estimated as 2xFMAs + 1xADDs. Excess vGPRs is #vGPRs - 4*N.
| N | FMAs | ADDs | Excess vGPRs | Cost | Cost/N^2 | Source |
|---|---|---|---|---|---|---|
| 2 | 0 | 4 | 4 | 1 | ||
| 3 | 6 | 6 | 1 | 18 | 2 | FFT-3 |
| 4 | 0 | 16 | 5 | 16 | 1 | FFT-4 |
| 5 | 12 | 24 | 4 | 28 | 1.1 | FFT-5 |
| 6 | 12 | 24 | 11 | 28 | 0.8 | FFT-6 |
| 7 | 10 | 62 | 13 | 82 | 1.7 | FFT-7 |
| 8 | 4 | 52 | 9 | 60 | 0.9 | FFT-8 |
| 9 | 20 | 72 | 17 | 112 | 1.4 | FFT-9 |
| 10 | 24 | 68 | 13 | 116 | 1.2 | FFT-10 |
| 11 | 110 | 30 | 33 | 250 | 2.1 | FFT-11 |
| 12 | 24 | 72 | 13 | 120 | 0.8 | FFT-12 |
| 13 | 156 | 36 | 25 | 348 | 2.1 | FFT-13 |
| 14 | 20 | 152 | 13 | 192 | 1 | FFT-14 |
| 15 | 66 | 102 | 15 | 234 | 1 | FFT-15 |
| 16 | 28 | 124 | 13 | 180 | 0.7 | FFT-16 |