private static final Random random = new Random();

public static Matrix randomMatrix(int rows, int cols) {

double[][] data = new double[rows][cols];

for (int i = 0; i < rows; i++)

for (int j = 0; j < cols; j++)

data[i][j] = random.nextDouble();

return new Matrix(data);

}

public static void validateDimensions(Matrix a, Matrix b) {

if (a.getCols() != b.getRows()) {

throw new IllegalArgumentException(

String.format(

"Cannot multiply matrices: A is %d×%d but B is %d×%d. " +

"A's column count (%d) must equal B's row count (%d).",

a.getRows(), a.getCols(), b.getRows(), b.getCols(),

a.getCols(), b.getRows()

)

);

}

}

public static long measure(Runnable task) {

long start = System.nanoTime();

task.run();

long end = System.nanoTime();

return TimeUnit.NANOSECONDS.toMillis(end - start);

}

}