Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly
Sign up
Appearance settings

Commit ac9920a

Browse files
committed
Style fixes for FFT code.
1 parent a88c45a commit ac9920a

File tree

2 files changed

+65
-51
lines changed

2 files changed

+65
-51
lines changed

‎src/algorithms/math/fourier-transform/__test__/fastFourierTransform.test.js‎

Lines changed: 43 additions & 27 deletions
Original file line numberDiff line numberDiff line change
@@ -2,50 +2,65 @@ import fastFourierTransform from '../fastFourierTransform';
22
import ComplexNumber from '../../complex-number/ComplexNumber';
33

44
/**
5-
* @param {ComplexNumber[]} [seq1]
6-
* @param {ComplexNumber[]} [seq2]
7-
* @param {Number} [eps]
5+
* @param {ComplexNumber[]} sequence1
6+
* @param {ComplexNumber[]} sequence2
7+
* @param {Number} delta
88
* @return {boolean}
99
*/
10-
function approximatelyEqual(seq1, seq2, eps) {
11-
if (seq1.length !== seq2.length) { return false; }
10+
function sequencesApproximatelyEqual(sequence1, sequence2, delta) {
11+
if (sequence1.length !== sequence2.length) {
12+
return false;
13+
}
14+
15+
for (let numberIndex = 0; numberIndex < sequence1.length; numberIndex += 1) {
16+
if (Math.abs(sequence1[numberIndex].re - sequence2[numberIndex].re) > delta) {
17+
return false;
18+
}
1219

13-
for(leti=0;i<seq1.length;i+=1) {
14-
if(Math.abs(seq1[i].real-seq2[i].real)>eps){return false;}
15-
if(Math.abs(seq1[i].complex-seq2[i].complex)>eps){returnfalse;}
20+
if(Math.abs(sequence1[numberIndex].im-sequence2[numberIndex].im)>delta) {
21+
return false;
22+
}
1623
}
1724

1825
return true;
1926
}
2027

28+
const delta = 1e-6;
29+
2130
describe('fastFourierTransform', () => {
2231
it('should calculate the radix-2 discrete fourier transform after zero padding', () => {
23-
const eps = 1e-6;
24-
const in1 = [new ComplexNumber({ re: 0, im: 0 })];
25-
const expOut1 = [new ComplexNumber({ re: 0, im: 0 })];
26-
const out1 = fastFourierTransform(in1);
27-
const invOut1 = fastFourierTransform(out1, true);
28-
expect(approximatelyEqual(expOut1, out1, eps)).toBe(true);
29-
expect(approximatelyEqual(in1, invOut1, eps)).toBe(true);
32+
const input = [new ComplexNumber({ re: 0, im: 0 })];
33+
const expectedOutput = [new ComplexNumber({ re: 0, im: 0 })];
34+
const output = fastFourierTransform(input);
35+
const invertedOutput = fastFourierTransform(output, true);
3036

31-
const in2 = [
37+
expect(sequencesApproximatelyEqual(expectedOutput, output, delta)).toBe(true);
38+
expect(sequencesApproximatelyEqual(input, invertedOutput, delta)).toBe(true);
39+
});
40+
41+
it('should calculate the radix-2 discrete fourier transform after zero padding', () => {
42+
const input = [
3243
new ComplexNumber({ re: 1, im: 2 }),
3344
new ComplexNumber({ re: 2, im: 3 }),
3445
new ComplexNumber({ re: 8, im: 4 }),
3546
];
3647

37-
const expOut2 = [
48+
const expectedOutput = [
3849
new ComplexNumber({ re: 11, im: 9 }),
3950
new ComplexNumber({ re: -10, im: 0 }),
4051
new ComplexNumber({ re: 7, im: 3 }),
4152
new ComplexNumber({ re: -4, im: -4 }),
4253
];
43-
const out2 = fastFourierTransform(in2);
44-
const invOut2 = fastFourierTransform(out2, true);
45-
expect(approximatelyEqual(expOut2, out2, eps)).toBe(true);
46-
expect(approximatelyEqual(in2, invOut2, eps)).toBe(true);
4754

48-
const in3 = [
55+
const output = fastFourierTransform(input);
56+
const invertedOut = fastFourierTransform(output, true);
57+
58+
expect(sequencesApproximatelyEqual(expectedOutput, output, delta)).toBe(true);
59+
expect(sequencesApproximatelyEqual(input, invertedOut, delta)).toBe(true);
60+
});
61+
62+
it('should calculate the radix-2 discrete fourier transform after zero padding', () => {
63+
const input = [
4964
new ComplexNumber({ re: -83656.9359385182, im: 98724.08038374918 }),
5065
new ComplexNumber({ re: -47537.415125808424, im: 88441.58381765135 }),
5166
new ComplexNumber({ re: -24849.657029355192, im: -72621.79007878687 }),
@@ -58,7 +73,7 @@ describe('fastFourierTransform', () => {
5873
new ComplexNumber({ re: -39327.43830818355, im: 30611.949874562706 }),
5974
];
6075

61-
const expOut3 = [
76+
const expectedOutput = [
6277
new ComplexNumber({ re: -203215.3322151, im: -100242.4827503 }),
6378
new ComplexNumber({ re: 99217.0805705, im: 270646.9331932 }),
6479
new ComplexNumber({ re: -305990.9040412, im: 68224.8435751 }),
@@ -77,9 +92,10 @@ describe('fastFourierTransform', () => {
7792
new ComplexNumber({ re: -179002.5662573, im: 239821.0124341 }),
7893
];
7994

80-
const out3 = fastFourierTransform(in3);
81-
const invOut3 = fastFourierTransform(out3, true);
82-
expect(approximatelyEqual(expOut3, out3, eps)).toBe(true);
83-
expect(approximatelyEqual(in3, invOut3, eps)).toBe(true);
95+
const output = fastFourierTransform(input);
96+
const invertedOutput = fastFourierTransform(output, true);
97+
98+
expect(sequencesApproximatelyEqual(expectedOutput, output, delta)).toBe(true);
99+
expect(sequencesApproximatelyEqual(input, invertedOutput, delta)).toBe(true);
84100
});
85101
});

‎src/algorithms/math/fourier-transform/fastFourierTransform.js‎

Lines changed: 22 additions & 24 deletions
Original file line numberDiff line numberDiff line change
@@ -10,68 +10,66 @@ import bitLength from '../bits/bitLength';
1010
*/
1111
function reverseBits(input, bitsCount) {
1212
let reversedBits = 0;
13+
1314
for (let i = 0; i < bitsCount; i += 1) {
1415
reversedBits *= 2;
15-
if (Math.floor(input / (1 << i)) % 2 === 1) { reversedBits += 1; }
16+
17+
if (Math.floor(input / (1 << i)) % 2 === 1) {
18+
reversedBits += 1;
19+
}
1620
}
21+
1722
return reversedBits;
1823
}
1924

2025
/**
2126
* Returns the radix-2 fast fourier transform of the given array.
2227
* Optionally computes the radix-2 inverse fast fourier transform.
2328
*
24-
* @param {ComplexNumber[]} [inputData]
25-
* @param {Boolean} [inverse]
29+
* @param {ComplexNumber[]} inputData
30+
* @param {boolean} [inverse]
2631
* @return {ComplexNumber[]}
2732
*/
2833
export default function fastFourierTransform(inputData, inverse = false) {
2934
const bitsCount = bitLength(inputData.length - 1);
3035
const N = 1 << bitsCount;
3136

3237
while (inputData.length < N) {
33-
inputData.push(new ComplexNumber({
34-
real: 0,
35-
imaginary: 0,
36-
}));
38+
inputData.push(new ComplexNumber());
3739
}
3840

3941
const output = [];
40-
for (let i = 0; i < N; i += 1) { output[i] = inputData[reverseBits(i, bitsCount)]; }
42+
for (let i = 0; i < N; i += 1) {
43+
output[i] = inputData[reverseBits(i, bitsCount)];
44+
}
4145

4246
for (let blockLength = 2; blockLength <= N; blockLength *= 2) {
43-
let phaseStep;
44-
if (inverse) {
45-
phaseStep = new ComplexNumber({
46-
real: Math.cos(2 * Math.PI / blockLength),
47-
imaginary: -1 * Math.sin(2 * Math.PI / blockLength),
48-
});
49-
} else {
50-
phaseStep = new ComplexNumber({
51-
real: Math.cos(2 * Math.PI / blockLength),
52-
imaginary: Math.sin(2 * Math.PI / blockLength),
53-
});
54-
}
47+
const imaginarySign = inverse ? -1 : 1;
48+
const phaseStep = new ComplexNumber({
49+
re: Math.cos(2 * Math.PI / blockLength),
50+
im: imaginarySign * Math.sin(2 * Math.PI / blockLength),
51+
});
5552

5653
for (let blockStart = 0; blockStart < N; blockStart += blockLength) {
57-
let phase = new ComplexNumber({
58-
real: 1,
59-
imaginary: 0,
60-
});
54+
let phase = new ComplexNumber({ re: 1, im: 0 });
6155

6256
for (let idx = blockStart; idx < blockStart + blockLength / 2; idx += 1) {
6357
const upd1 = output[idx].add(output[idx + blockLength / 2].multiply(phase));
6458
const upd2 = output[idx].subtract(output[idx + blockLength / 2].multiply(phase));
59+
6560
output[idx] = upd1;
6661
output[idx + blockLength / 2] = upd2;
62+
6763
phase = phase.multiply(phaseStep);
6864
}
6965
}
7066
}
67+
7168
if (inverse) {
7269
for (let idx = 0; idx < N; idx += 1) {
7370
output[idx] /= N;
7471
}
7572
}
73+
7674
return output;
7775
}

0 commit comments

Comments
(0)

AltStyle によって変換されたページ (->オリジナル) /