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Updates to FastFourierTransformer, following changes to RootsOfUnity in r1238179. See MATH-677. 

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1238180 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Sebastien Brisard 2012-01-31 07:02:58 +00:00
parent 08ca1e7a0a
commit c643b22bfc
1 changed files with 6 additions and 7 deletions
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13
src/main/java/org/apache/commons/math/transform/FastFourierTransformer.java
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@ -189,8 +189,7 @@ public class FastFourierTransformer implements Serializable {
* not a power of two
*/
public Complex[] transform(Complex[] f) {
// TODO Is this necessary?
roots.computeOmega(f.length);
roots.computeOmega(-f.length);
if (unitary) {
final double s = 1.0 / FastMath.sqrt(f.length);
return TransformUtils.scaleArray(fft(f), s);
@ -243,7 +242,7 @@ public class FastFourierTransformer implements Serializable {
* not a power of two
*/
public Complex[] inverseTransform(Complex[] f) {
roots.computeOmega(-f.length); // pass negative argument
roots.computeOmega(f.length);
final double s = 1.0 / (unitary ? FastMath.sqrt(f.length) : f.length);
return TransformUtils.scaleArray(fft(f), s);
}
@ -278,11 +277,11 @@ public class FastFourierTransformer implements Serializable {
for (int i = 0; i < n; i++) {
repacked[i] = new Complex(f[2 * i], f[2 * i + 1]);
}
roots.computeOmega(isInverse ? -n : n);
roots.computeOmega(isInverse ? n : -n);
Complex[] z = fft(repacked);
// reconstruct the FFT result for the original array
roots.computeOmega(isInverse ? -2 * n : 2 * n);
roots.computeOmega(isInverse ? 2 * n : -2 * n);
transformed[0] = new Complex(2 * (z[0].getReal() + z[0].getImaginary()), 0.0);
transformed[n] = new Complex(2 * (z[0].getReal() - z[0].getImaginary()), 0.0);
for (int i = 1; i < n; i++) {
@ -352,8 +351,8 @@ public class FastFourierTransformer implements Serializable {
f[i] = a.add(b);
f[i + 2] = a.subtract(b);
// omegaCount indicates forward or inverse transform
f[i + 1] = roots.isForward() ? e2 : e1;
f[i + 3] = roots.isForward() ? e1 : e2;
f[i + 1] = roots.isCounterClockWise() ? e1 : e2;
f[i + 3] = roots.isCounterClockWise() ? e2 : e1;
}
// iterations from bottom to top take O(N*logN) time