/**
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* @license
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* Copyright 2018 Google LLC. All Rights Reserved.
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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* =============================================================================
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*/
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import {TypedArray} from '../types';
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/**
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* Merges real and imaginary Float32Arrays into a single complex Float32Array.
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*
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* The memory layout is interleaved as follows:
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* real: [r0, r1, r2]
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* imag: [i0, i1, i2]
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* complex: [r0, i0, r1, i1, r2, i2]
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*
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* This is the inverse of splitRealAndImagArrays.
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*
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* @param real The real values of the complex tensor values.
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* @param imag The imag values of the complex tensor values.
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* @returns A complex tensor as a Float32Array with merged values.
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*/
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export function mergeRealAndImagArrays(
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real: Float32Array, imag: Float32Array): Float32Array {
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if (real.length !== imag.length) {
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throw new Error(
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`Cannot merge real and imag arrays of different lengths. real:` +
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`${real.length}, imag: ${imag.length}.`);
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}
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const result = new Float32Array(real.length * 2);
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for (let i = 0; i < result.length; i += 2) {
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result[i] = real[i / 2];
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result[i + 1] = imag[i / 2];
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}
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return result;
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}
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/**
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* Splits a complex Float32Array into real and imag parts.
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*
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* The memory layout is interleaved as follows:
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* complex: [r0, i0, r1, i1, r2, i2]
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* real: [r0, r1, r2]
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* imag: [i0, i1, i2]
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*
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* This is the inverse of mergeRealAndImagArrays.
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*
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* @param complex The complex tensor values.
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* @returns An object with real and imag Float32Array components of the complex
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* tensor.
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*/
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export function splitRealAndImagArrays(complex: Float32Array):
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{real: Float32Array, imag: Float32Array} {
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const real = new Float32Array(complex.length / 2);
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const imag = new Float32Array(complex.length / 2);
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for (let i = 0; i < complex.length; i += 2) {
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real[i / 2] = complex[i];
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imag[i / 2] = complex[i + 1];
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}
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return {real, imag};
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}
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/**
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* Extracts even indexed complex values in the given array.
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* @param complex The complex tensor values
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*/
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export function complexWithEvenIndex(complex: Float32Array):
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{real: Float32Array, imag: Float32Array} {
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const len = Math.ceil(complex.length / 4);
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const real = new Float32Array(len);
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const imag = new Float32Array(len);
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for (let i = 0; i < complex.length; i += 4) {
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real[Math.floor(i / 4)] = complex[i];
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imag[Math.floor(i / 4)] = complex[i + 1];
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}
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return {real, imag};
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}
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/**
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* Extracts odd indexed comple values in the given array.
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* @param complex The complex tensor values
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*/
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export function complexWithOddIndex(complex: Float32Array):
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{real: Float32Array, imag: Float32Array} {
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const len = Math.floor(complex.length / 4);
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const real = new Float32Array(len);
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const imag = new Float32Array(len);
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for (let i = 2; i < complex.length; i += 4) {
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real[Math.floor(i / 4)] = complex[i];
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imag[Math.floor(i / 4)] = complex[i + 1];
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}
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return {real, imag};
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}
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/**
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* Get the map representing a complex value in the given array.
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* @param complex The complex tensor values.
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* @param index An index of the target complex value.
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*/
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export function getComplexWithIndex(
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complex: Float32Array, index: number): {real: number, imag: number} {
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const real = complex[index * 2];
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const imag = complex[index * 2 + 1];
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return {real, imag};
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}
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/**
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* Insert a given complex value into the TypedArray.
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* @param data The array in which the complex value is inserted.
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* @param c The complex value to be inserted.
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* @param index An index of the target complex value.
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*/
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export function assignToTypedArray(
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data: TypedArray, real: number, imag: number, index: number) {
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data[index * 2] = real;
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data[index * 2 + 1] = imag;
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}
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/**
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* Make the list of exponent terms used by FFT.
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*/
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export function exponents(
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n: number, inverse: boolean): {real: Float32Array, imag: Float32Array} {
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const real = new Float32Array(n / 2);
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const imag = new Float32Array(n / 2);
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for (let i = 0; i < Math.ceil(n / 2); i++) {
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const x = (inverse ? 2 : -2) * Math.PI * (i / n);
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real[i] = Math.cos(x);
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imag[i] = Math.sin(x);
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}
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return {real, imag};
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}
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/**
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* Make the exponent term used by FFT.
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*/
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export function exponent(
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k: number, n: number, inverse: boolean): {real: number, imag: number} {
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const x = (inverse ? 2 : -2) * Math.PI * (k / n);
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const real = Math.cos(x);
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const imag = Math.sin(x);
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return {real, imag};
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}
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