private void FftStageN(int stageNr, WWComplex[] x, WWComplex[] y) { /* * stage0: 2つの入力データにバタフライ演算 (n=8の時) 4回 (nRepeat=4, nSubRepeat=2) * y[0] = x[0] + w_n^(0*4) * x[1] * y[1] = x[0] + w_n^(1*4) * x[1] * * y[2] = x[2] + w_n^(0*4) * x[3] * y[3] = x[2] + w_n^(1*4) * x[3] * * y[4] = x[4] + w_n^(0*4) * x[5] * y[5] = x[4] + w_n^(1*4) * x[5] * * y[6] = x[6] + w_n^(0*4) * x[7] * y[7] = x[6] + w_n^(1*4) * x[7] */ /* * stage1: 4つの入力データにバタフライ演算 (n=8の時) 2回 (nRepeat=2, nSubRepeat=4) * y[0] = x[0] + w_n^(0*2) * x[2] * y[1] = x[1] + w_n^(1*2) * x[3] * y[2] = x[0] + w_n^(2*2) * x[2] * y[3] = x[1] + w_n^(3*2) * x[3] * * y[4] = x[4] + w_n^(0*2) * x[6] * y[5] = x[5] + w_n^(1*2) * x[7] * y[6] = x[4] + w_n^(2*2) * x[6] * y[7] = x[5] + w_n^(3*2) * x[7] */ /* * stage2: 8つの入力データにバタフライ演算 (n=8の時) 1回 (nRepeat=1, nSubRepeat=8) * y[0] = x[0] + w_n^(0*1) * x[4] * y[1] = x[1] + w_n^(1*1) * x[5] * y[2] = x[2] + w_n^(2*1) * x[6] * y[3] = x[3] + w_n^(3*1) * x[7] * y[4] = x[0] + w_n^(4*1) * x[4] * y[5] = x[1] + w_n^(5*1) * x[5] * y[6] = x[2] + w_n^(6*1) * x[6] * y[7] = x[3] + w_n^(7*1) * x[7] */ /* * stageN: */ int nRepeat = Pow2(mNumStage - stageNr - 1); int nSubRepeat = mNumPoints / nRepeat; var t = new WWComplex(); for (int i=0; i<nRepeat; ++i) { int offsBase = i * nSubRepeat; bool allZero = true; for (int j=0; j < nSubRepeat/2; ++j) { int offs = offsBase + (j % (nSubRepeat/2)); if (Double.Epsilon < x[offs].Magnitude()) { allZero = false; break; } if (Double.Epsilon < x[offs + nSubRepeat / 2].Magnitude()) { allZero = false; break; } } if (allZero) { for (int j=0; j < nSubRepeat / 2; ++j) { y[j + offsBase].Set(0, 0); } } else { for (int j=0; j < nSubRepeat; ++j) { int offs = offsBase + (j % (nSubRepeat / 2)); y[j + offsBase].CopyFrom(x[offs]); t.CopyFrom(mWn[j * nRepeat]); t.Mul(x[offs + nSubRepeat / 2]); y[j + offsBase].Add(t); } } } }
private void FftStageN(int stageNr, WWComplex[] x, WWComplex[] y) { /* * stage0: 2つの入力データにバタフライ演算 (n=8の時) 4回 (nRepeat=4, nSubRepeat=2) * y[0] = x[0] + w_n^(0*4) * x[1] * y[1] = x[0] + w_n^(1*4) * x[1] * * y[2] = x[2] + w_n^(0*4) * x[3] * y[3] = x[2] + w_n^(1*4) * x[3] * * y[4] = x[4] + w_n^(0*4) * x[5] * y[5] = x[4] + w_n^(1*4) * x[5] * * y[6] = x[6] + w_n^(0*4) * x[7] * y[7] = x[6] + w_n^(1*4) * x[7] */ /* * stage1: 4つの入力データにバタフライ演算 (n=8の時) 2回 (nRepeat=2, nSubRepeat=4) * y[0] = x[0] + w_n^(0*2) * x[2] * y[1] = x[1] + w_n^(1*2) * x[3] * y[2] = x[0] + w_n^(2*2) * x[2] * y[3] = x[1] + w_n^(3*2) * x[3] * * y[4] = x[4] + w_n^(0*2) * x[6] * y[5] = x[5] + w_n^(1*2) * x[7] * y[6] = x[4] + w_n^(2*2) * x[6] * y[7] = x[5] + w_n^(3*2) * x[7] */ /* * stage2: 8つの入力データにバタフライ演算 (n=8の時) 1回 (nRepeat=1, nSubRepeat=8) * y[0] = x[0] + w_n^(0*1) * x[4] * y[1] = x[1] + w_n^(1*1) * x[5] * y[2] = x[2] + w_n^(2*1) * x[6] * y[3] = x[3] + w_n^(3*1) * x[7] * y[4] = x[0] + w_n^(4*1) * x[4] * y[5] = x[1] + w_n^(5*1) * x[5] * y[6] = x[2] + w_n^(6*1) * x[6] * y[7] = x[3] + w_n^(7*1) * x[7] */ /* * stageN: */ int nRepeat = Pow2(mNumStage - stageNr - 1); int nSubRepeat = mNumPoints / nRepeat; var t = new WWComplex(); for (int i = 0; i < nRepeat; ++i) { int offsBase = i * nSubRepeat; bool allZero = true; for (int j = 0; j < nSubRepeat / 2; ++j) { int offs = offsBase + (j % (nSubRepeat / 2)); if (Double.Epsilon < x[offs].Magnitude()) { allZero = false; break; } if (Double.Epsilon < x[offs + nSubRepeat / 2].Magnitude()) { allZero = false; break; } } if (allZero) { for (int j = 0; j < nSubRepeat / 2; ++j) { y[j + offsBase].Set(0, 0); } } else { for (int j = 0; j < nSubRepeat; ++j) { int offs = offsBase + (j % (nSubRepeat / 2)); y[j + offsBase].CopyFrom(x[offs]); t.CopyFrom(mWn[j * nRepeat]); t.Mul(x[offs + nSubRepeat / 2]); y[j + offsBase].Add(t); } } } }
private void Butterfly(WWComplex vFrom0, WWComplex vFrom1, WWComplex wn, WWComplex[] vTo, int toPos) { vTo[toPos].CopyFrom(vFrom0); WWComplex t = new WWComplex(vFrom1); t.Mul(wn); vTo[toPos].Mul(t); vTo[toPos + 1].CopyFrom(vFrom0); t.Mul(-1); vTo[toPos + 1].Mul(t); }