看起来好像
calloc达到了一个阈值，在该阈值下，操作系统会要求将内存清零，而无需手动对其进行初始化。查看源代码，
numpy.zeros最终委托来
calloc获取清零的内存块，如果与进行比较
numpy.empty，则不执行初始化：
In [15]: %timeit np.zeros((5000, 5000))The slowest run took 12.65 times longer than the fastest. This could mean that an intermediate result is being cached.100000 loops, best of 3: 10 µs per loopIn [16]: %timeit np.empty((5000, 5000))The slowest run took 5.05 times longer than the fastest. This could mean that an intermediate result is being cached.100000 loops, best of 3: 10.3 µs per loop
您会看到
np.zeros5000x5000阵列没有初始化开销。
实际上，在您尝试访问该内存之前，该操作系统甚至没有“真正”分配该内存。在无数TB可用空间的机器上，对TB级阵列的请求成功完成：
In [23]: x = np.zeros(2**40) # No MemoryError!
