矩阵运算优化

优化原理：CPU缓存机制

import java.util.Random;

public class MatrixCalculate {
    public static void main(String[] args) {
        int size = 2000;
        float[][] m1 = new float[size][size];
        float[][] m2 = new float[size][size];
        randomFill(m1);
        randomFill(m2);

        //m1·m2
        float[][] result1 = new float[size][size];
        long start = System.currentTimeMillis();
        for (int i = 0; i < size; i++) {
            for (int k = 0; k < size; k++) {
                for (int j = 0; j < size; j++) {
                    result1[i][j] += m1[i][k] * m2[k][j];
                }
            }
        }
        System.out.println("耗时：" + (System.currentTimeMillis() - start));
        float[][] result2 = new float[size][size];
        start = System.currentTimeMillis();
        for (int i = 0; i < size; i++) {
            for (int j = 0; j < size; j++) {
                for (int k = 0; k < size; k++) {
                    result2[i][j] += m1[i][k] * m2[k][j];
                }
            }
        }
        System.out.println("耗时：" + (System.currentTimeMillis() - start));
        for (int i = 0; i < size; i++) {
            for (int j = 0; j < size; j++) {
                if (result1[i][j] != result2[i][j]) {
                    System.out.println("======ERROR====");
                    System.out.println(result1[i][j]);
                    System.out.println(result2[i][j]);
                }
            }
        }
    }

    public static void randomFill(float[][] floats) {
        for (int i = 0; i < floats.length; i++) {
            for (int j = 0; j < floats[i].length; j++) {
                floats[i][j] = new Random().nextFloat();
            }
        }
    }
}