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);
}
}
}
}
