DAS_2024_1/emelyanov_artem_lab_5/MatrixMultiplication.java

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

public class MatrixMultiplication {
    public static int[][] multiply(int[][] matrixA, int[][] matrixB, int numThreads) {
        int n = matrixA.length;
        int[][] result = new int[n][n];

        if (numThreads == 1) {
            // Последовательное умножение
            for (int i = 0; i < n; i++) {
                multiplyRow(matrixA, matrixB, result, i);
            }
        } else {
            // Многопоточное умножение
            ExecutorService executor = Executors.newFixedThreadPool(numThreads);

            for (int i = 0; i < n; i++) {
                final int row = i;
                executor.submit(() -> multiplyRow(matrixA, matrixB, result, row));
            }

            executor.shutdown();
            try {
                // Ожидаем завершения всех задач
                executor.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        return result;
    }

    private static void multiplyRow(int[][] matrixA, int[][] matrixB, int[][] result, int row) {
        int n = matrixA.length;
        for (int j = 0; j < n; j++) {
            for (int k = 0; k < n; k++) {
                result[row][j] += matrixA[row][k] * matrixB[k][j];
            }
        }
    }
}