DefaultFFTInstance.java

/*-
 *
 *  * Copyright 2015 Skymind,Inc.
 *  *
 *  *    Licensed under the Apache License, Version 2.0 (the "License");
 *  *    you may not use this file except in compliance with the License.
 *  *    You may obtain a copy of the License at
 *  *
 *  *        http://www.apache.org/licenses/LICENSE-2.0
 *  *
 *  *    Unless required by applicable law or agreed to in writing, software
 *  *    distributed under the License is distributed on an "AS IS" BASIS,
 *  *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  *    See the License for the specific language governing permissions and
 *  *    limitations under the License.
 *
 *
 */

package org.nd4j.linalg.fft;

import org.nd4j.linalg.api.complex.IComplexNDArray;
import org.nd4j.linalg.api.ndarray.INDArray;
import org.nd4j.linalg.api.ops.Op;
import org.nd4j.linalg.api.ops.impl.transforms.VectorFFT;
import org.nd4j.linalg.api.ops.impl.transforms.VectorIFFT;
import org.nd4j.linalg.factory.Nd4j;
import org.nd4j.linalg.util.ArrayUtil;
import org.nd4j.linalg.util.ComplexNDArrayUtil;

/**
 * Default FFT instance
 * that will work that is backend agnostic.
 *
 * @author Adam Gibson
 */
public class DefaultFFTInstance extends BaseFFTInstance {

    /**
     * FFT along a particular dimension
     *
     * @param transform   the ndarray to op
     * @param numElements the desired number of elements in each fft
     * @return the ffted output
     */
    @Override
    public IComplexNDArray fft(INDArray transform, int numElements, int dimension) {
        IComplexNDArray inputC = Nd4j.createComplex(transform);
        if (inputC.isVector())
            return (IComplexNDArray) Nd4j.getExecutioner().execAndReturn(getFftOp(inputC, numElements));
        else {
            int[] finalShape = ArrayUtil.replace(transform.shape(), dimension, numElements);
            IComplexNDArray transform2 = Nd4j.createComplex(transform);
            IComplexNDArray result = transform2.dup();

            int desiredElementsAlongDimension = result.size(dimension);

            if (numElements > desiredElementsAlongDimension) {
                result = ComplexNDArrayUtil.padWithZeros(result, finalShape);
            }

            else if (numElements < desiredElementsAlongDimension)
                result = ComplexNDArrayUtil.truncate(result, numElements, dimension);

            return rawfft(result, numElements, dimension);
        }
    }

    /**
     * 1d discrete fourier op, note that this will
     * throw an exception if the passed in input
     * isn't a vector.
     * See matlab's fft2 for more information
     *
     * @param inputC the input to op
     * @return the the discrete fourier op of the passed in input
     */
    @Override
    public IComplexNDArray fft(IComplexNDArray inputC, int numElements, int dimension) {
        if (inputC.isVector())
            return (IComplexNDArray) Nd4j.getExecutioner().execAndReturn(getFftOp(inputC, numElements));
        else
            return rawfft(inputC, numElements, dimension);

    }


    /**
     * IFFT along a particular dimension
     *
     * @param transform   the ndarray to op
     * @param numElements the desired number of elements in each fft
     * @param dimension   the dimension to do fft along
     * @return the iffted output
     */
    @Override
    public IComplexNDArray ifft(INDArray transform, int numElements, int dimension) {
        IComplexNDArray inputC = Nd4j.createComplex(transform);
        if (inputC.isVector())
            return (IComplexNDArray) Nd4j.getExecutioner().execAndReturn(getIfftOp(inputC, numElements));
        else
            return rawifft(inputC, numElements, dimension);

    }

    /**
     * 1d discrete fourier op, note that this will
     * throw an exception if the passed in input
     * isn't a vector.
     * See matlab's fft2 for more information
     *
     * @param inputC the input to op
     * @return the the discrete fourier op of the passed in input
     */
    @Override
    public IComplexNDArray ifft(IComplexNDArray inputC, int numElements, int dimension) {
        if (inputC.isVector())
            return (IComplexNDArray) Nd4j.getExecutioner().execAndReturn(getIfftOp(inputC, numElements));
        else {
            return rawifft(inputC, numElements, dimension);
        }
    }

    /**
     * FFT along a particular dimension
     *
     * @param transform   the ndarray to op
     * @param numElements the desired number of elements in each fft
     * @return the ffted output
     */
    @Override
    public IComplexNDArray ifft(INDArray transform, int numElements) {
        IComplexNDArray inputC = Nd4j.createComplex(transform);
        if (inputC.isVector())
            return (IComplexNDArray) Nd4j.getExecutioner().execAndReturn(getIfftOp(inputC, numElements));
        else {
            return rawifft(inputC, numElements, inputC.shape().length - 1);
        }
    }

    /**
     * 1d discrete fourier op, note that this will
     * throw an exception if the passed in input
     * isn't a vector.
     * See matlab's fft2 for more information
     *
     * @param inputC the input to op
     * @return the the discrete fourier op of the passed in input
     */
    @Override
    public IComplexNDArray ifft(IComplexNDArray inputC) {
        if (inputC.isVector())
            return (IComplexNDArray) Nd4j.getExecutioner().execAndReturn(getIfftOp(inputC, inputC.length()));
        else
            return rawifft(inputC, inputC.size(inputC.shape().length - 1), inputC.shape().length - 1);

    }


    /**
     * Underlying fft algorithm
     *
     * @param transform the ndarray to op
     * @param n         the desired number of elements
     * @param dimension the dimension to do fft along
     * @return the transformed ndarray
     */
    @Override
    public IComplexNDArray rawfft(IComplexNDArray transform, int n, int dimension) {
        IComplexNDArray result = transform.dup();
        result = preProcess(result, transform, n, dimension);
        Nd4j.getExecutioner().iterateOverAllRows(getFftOp(result, n));
        result = postProcess(result, dimension);
        return result;
    }


    @Override
    public IComplexNDArray rawifft(IComplexNDArray transform, int n, int dimension) {
        IComplexNDArray result = transform.dup();
        result = preProcess(result, transform, n, dimension);
        Nd4j.getExecutioner().iterateOverAllRows(getIfftOp(result, n));
        result = postProcess(result, dimension);
        return result;
    }


    protected IComplexNDArray postProcess(IComplexNDArray result, int dimension) {
        if (dimension != result.shape().length - 1)
            result = result.swapAxes(result.shape().length - 1, dimension);
        return result;
    }



    protected IComplexNDArray preProcess(IComplexNDArray result, IComplexNDArray transform, int n, int dimension) {
        if (dimension < 0)
            dimension = transform.shape().length - 1 - dimension;
        if (transform.size(dimension) != n) {
            int[] shape = ArrayUtil.copy(result.shape());
            shape[dimension] = n;
            if (transform.size(dimension) > n) {
                result = ComplexNDArrayUtil.truncate(result, n, dimension);
            } else
                result = ComplexNDArrayUtil.padWithZeros(result, shape);

        }


        if (dimension != result.shape().length - 1)
            result = result.swapAxes(result.shape().length - 1, dimension);

        return result;

    }



    protected Op getIfftOp(INDArray arr, int n) {
        return new VectorIFFT(arr, n);
    }

    protected Op getFftOp(INDArray arr, int n) {
        return new VectorFFT(arr, n);
    }


}