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/*
 * Copyright (c) 2022, Peter Abeles. All Rights Reserved.
 *
 * This file is part of BoofCV (http://boofcv.org).
 *
 * 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 boofcv.struct.kmeans;

import boofcv.concurrency.BoofConcurrency;
import boofcv.struct.feature.TupleDesc_B;
import lombok.Getter;
import lombok.Setter;
import org.ddogleg.struct.DogArray;
import org.ddogleg.struct.DogArray_I32;
import org.ddogleg.struct.LArrayAccessor;
import pabeles.concurrency.GrowArray;

import java.util.Arrays;

/**
 * Concurrent implementation of {@link ComputeMedianTuple_B}
 *
 * @author Peter Abeles
 */
public class ComputeMedianTuple_MT_B extends ComputeMedianTuple_B {

	/**
	 * Minimum list size for it to use concurrent code. If a list is small it will run slower than the single
	 * thread version. By default this is zero since the optimal value is use case specific.
	 */
	@Getter @Setter int minimumForConcurrent = 0;

	GrowArray threadData;

	public ComputeMedianTuple_MT_B( int DOF ) {
		super(DOF);

		threadData = new GrowArray<>(ThreadData::new);
	}

	@Override
	protected void countBitsInEachCluster( LArrayAccessor points, DogArray_I32 assignments ) {
		if (points.size() < minimumForConcurrent) {
			super.countBitsInEachCluster(points, assignments);
			return;
		}
		int numClusters = super.assignmentCounts.size;

		// Compute the sum of all points in each cluster
		BoofConcurrency.loopBlocks(0, points.size(), threadData, ( data, idx0, idx1 ) -> {
			final TupleDesc_B tuple = data.point;
			final DogArray bitCounts = data.bitCounts;
			final DogArray_I32 assignmentCounts = data.assignmentCounts;

			assignmentCounts.reset().resize(numClusters, 0);
			bitCounts.resize(numClusters);
			for (int i = 0; i < bitCounts.size; i++) {
				Arrays.fill(bitCounts.data[i], 0);
			}

			// Compute the sum of all points in each cluster
			for (int pointIdx = idx0; pointIdx < idx1; pointIdx++) {
				// See which cluster this point was assigned to and increment its counter
				int clusterIdx = assignments.get(pointIdx);
				assignmentCounts.data[clusterIdx]++;

				points.getCopy(pointIdx, tuple);

				// Increment the counter for each "true" bit in the tuple
				int[] bitCount = bitCounts.get(clusterIdx);
				int bit = 0;
				while (bit + 32 < dof) {
					// Unroll for speed
					int value = tuple.data[bit/32];
					if ((value & 0x00000001) != 0) bitCount[bit]++;
					if ((value & 0x00000002) != 0) bitCount[bit + 1]++;
					if ((value & 0x00000004) != 0) bitCount[bit + 2]++;
					if ((value & 0x00000008) != 0) bitCount[bit + 3]++;
					if ((value & 0x00000010) != 0) bitCount[bit + 4]++;
					if ((value & 0x00000020) != 0) bitCount[bit + 5]++;
					if ((value & 0x00000040) != 0) bitCount[bit + 6]++;
					if ((value & 0x00000080) != 0) bitCount[bit + 7]++;
					if ((value & 0x00000100) != 0) bitCount[bit + 8]++;
					if ((value & 0x00000200) != 0) bitCount[bit + 9]++;
					if ((value & 0x00000400) != 0) bitCount[bit + 10]++;
					if ((value & 0x00000800) != 0) bitCount[bit + 11]++;
					if ((value & 0x00001000) != 0) bitCount[bit + 12]++;
					if ((value & 0x00002000) != 0) bitCount[bit + 13]++;
					if ((value & 0x00004000) != 0) bitCount[bit + 14]++;
					if ((value & 0x00008000) != 0) bitCount[bit + 15]++;
					if ((value & 0x00010000) != 0) bitCount[bit + 16]++;
					if ((value & 0x00020000) != 0) bitCount[bit + 17]++;
					if ((value & 0x00040000) != 0) bitCount[bit + 18]++;
					if ((value & 0x00080000) != 0) bitCount[bit + 19]++;
					if ((value & 0x00100000) != 0) bitCount[bit + 20]++;
					if ((value & 0x00200000) != 0) bitCount[bit + 21]++;
					if ((value & 0x00400000) != 0) bitCount[bit + 22]++;
					if ((value & 0x00800000) != 0) bitCount[bit + 23]++;
					if ((value & 0x01000000) != 0) bitCount[bit + 24]++;
					if ((value & 0x02000000) != 0) bitCount[bit + 25]++;
					if ((value & 0x04000000) != 0) bitCount[bit + 26]++;
					if ((value & 0x08000000) != 0) bitCount[bit + 27]++;
					if ((value & 0x10000000) != 0) bitCount[bit + 28]++;
					if ((value & 0x20000000) != 0) bitCount[bit + 29]++;
					if ((value & 0x40000000) != 0) bitCount[bit + 30]++;
					if ((value & 0x80000000) != 0) bitCount[bit + 31]++;
					bit += 32;
				}
				// handle the remainder if it doesn't align with 32-bit integers
				for (; bit < dof; bit++) {
					if (!tuple.isBitTrue(bit))
						continue;
					bitCount[bit]++;
				}
			}
		});

		// stitch all the threads back together
		for (int threadIdx = 0; threadIdx < threadData.size(); threadIdx++) {
			ThreadData data = threadData.get(threadIdx);
			for (int clusterIdx = 0; clusterIdx < numClusters; clusterIdx++) {
				super.assignmentCounts.data[clusterIdx] += data.assignmentCounts.data[clusterIdx];

				int[] allCounts = super.bitCounts.get(clusterIdx);
				int[] threadCounts = data.bitCounts.get(clusterIdx);

				for (int bitIdx = 0; bitIdx < dof; bitIdx++) {
					allCounts[bitIdx] += threadCounts[bitIdx];
				}
			}
		}
	}

	class ThreadData {
		DogArray bitCounts = new DogArray<>(() -> new int[dof]);
		TupleDesc_B point = new TupleDesc_B(dof);
		DogArray_I32 assignmentCounts = new DogArray_I32();
	}
}