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/*
 * MIT License
 *
 * Copyright (c) 2002-2023 Mikko Tommila
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package org.apfloat.internal;

import org.apfloat.ApfloatRuntimeException;
import org.apfloat.spi.NTTConvolutionStepStrategy;
import org.apfloat.spi.DataStorage;
import static org.apfloat.internal.LongModConstants.*;

/**
 * Steps of a three-NTT convolution for the long type.
 * This class implements the details of the element-by-element multiplication
 * and element-by-element squaring of the transformed elements.
 *
 * The in-place multiplication and squaring of the data elements is done
 * using a parallel algorithm, if the data fits in memory.
 *
 * All access to this class must be externally synchronized.
 *
 * @since 1.7.0
 * @version 1.9.0
 * @author Mikko Tommila
 */

public class LongNTTConvolutionStepStrategy
    extends LongModMath
    implements NTTConvolutionStepStrategy, Parallelizable
{
    // Runnable for multiplying elements in place
    private class MultiplyInPlaceRunnable
        implements Runnable
    {
        public MultiplyInPlaceRunnable(DataStorage sourceAndDestination, DataStorage source, long offset, long length)
        {
            this.sourceAndDestination = sourceAndDestination;
            this.source = source;
            this.offset = offset;
            this.length = length;
        }

        @Override
        public void run()
        {
            DataStorage.Iterator dest = this.sourceAndDestination.iterator(DataStorage.READ_WRITE, this.offset, this.offset + this.length),
                                 src = this.source.iterator(DataStorage.READ, this.offset, this.offset + this.length);

            while (this.length > 0)
            {
                dest.setLong(modMultiply(dest.getLong(), src.getLong()));

                dest.next();
                src.next();
                this.length--;
            }
        }

        private DataStorage sourceAndDestination,
                            source;
        private long offset,
                     length;
    }

    // Runnable for squaring elements in place
    private class SquareInPlaceRunnable
        implements Runnable
    {
        public SquareInPlaceRunnable(DataStorage sourceAndDestination, long offset, long length)
        {
            this.sourceAndDestination = sourceAndDestination;
            this.offset = offset;
            this.length = length;
        }

        @Override
        public void run()
        {
            DataStorage.Iterator iterator = this.sourceAndDestination.iterator(DataStorage.READ_WRITE, this.offset, this.offset + this.length);

            while (this.length > 0)
            {
                long value = iterator.getLong();
                iterator.setLong(modMultiply(value, value));

                iterator.next();
                this.length--;
            }
        }

        private DataStorage sourceAndDestination;
        private long offset,
                     length;
    }

    /**
     * Default constructor.
     */

    public LongNTTConvolutionStepStrategy()
    {
    }

    @Override
    public void multiplyInPlace(DataStorage sourceAndDestination, DataStorage source, int modulus)
        throws ApfloatRuntimeException
    {
        assert (sourceAndDestination != source);

        long size = sourceAndDestination.getSize();

        ParallelRunnable parallelRunnable = createMultiplyInPlaceParallelRunnable(sourceAndDestination, source, modulus);

        if (size <= Integer.MAX_VALUE &&                                        // Only if the size fits in an integer, but with memory arrays it should
            sourceAndDestination.isCached() && source.isCached())               // Only if the data storage supports efficient parallel random access
        {
            ParallelRunner.runParallel(parallelRunnable);
        }
        else
        {
            parallelRunnable.run();                                             // Just run in current thread without parallelization
        }
    }

    @Override
    public void squareInPlace(DataStorage sourceAndDestination, int modulus)
        throws ApfloatRuntimeException
    {
        long size = sourceAndDestination.getSize();

        ParallelRunnable parallelRunnable = createSquareInPlaceParallelRunnable(sourceAndDestination, modulus);

        if (size <= Integer.MAX_VALUE &&                                    // Only if the size fits in an integer, but with memory arrays it should
            sourceAndDestination.isCached())                                // Only if the data storage supports efficient parallel random access
        {
            ParallelRunner.runParallel(parallelRunnable);
        }
        else
        {
            parallelRunnable.run();                                         // Just run in current thread without parallelization
        }
    }

    /**
     * Create a ParallelRunnable for multiplying the elements in-place.
     *
     * @param sourceAndDestination The first source data storage, which is also the destination.
     * @param source The second source data storage.
     * @param modulus Which modulus to use (0, 1, 2)
     *
     * @return An object suitable for multiplying the elements in parallel.
     */

    protected ParallelRunnable createMultiplyInPlaceParallelRunnable(DataStorage sourceAndDestination, DataStorage source, int modulus)
    {
        long size = sourceAndDestination.getSize();

        setModulus(MODULUS[modulus]);

        ParallelRunnable parallelRunnable = new ParallelRunnable(size)
        {
            @Override
            public Runnable getRunnable(long offset, long length)
            {
                return new MultiplyInPlaceRunnable(sourceAndDestination, source, offset, length);
            }
        };
        return parallelRunnable;
    }

    /**
     * Create a ParallelRunnable for squaring the elements in-place.
     *
     * @param sourceAndDestination The source data storage, which is also the destination.
     * @param modulus Which modulus to use (0, 1, 2)
     *
     * @return An object suitable for squaring the elements in parallel.
     */

    protected ParallelRunnable createSquareInPlaceParallelRunnable(DataStorage sourceAndDestination, int modulus)
    {
        long size = sourceAndDestination.getSize();

        setModulus(MODULUS[modulus]);

        ParallelRunnable parallelRunnable = new ParallelRunnable(size)
        {
            @Override
            public Runnable getRunnable(long offset, long length)
            {
                return new SquareInPlaceRunnable(sourceAndDestination, offset, length);
            }
        };
        return parallelRunnable;
    }
}