fun mul(a, b: NativeDoubleArray, a_width, a_height, b_width: Int) `{
		int i, j, k;
		for (j = 0; j < a_height; j ++)
			for (i = 0; i < b_width; i ++) {
				float sum = 0.0;
				for (k = 0; k < a_width; k ++) sum += a[j*a_width + k] * b[k*b_width + i];
				self[j*b_width + i] = sum;
			}
	`}