为什么将numpy.dot输出到memmap不起作用? [英] Why does outputing numpy.dot to memmap does not work?

问题描述

如果我这样做:

a = np.ones((10,1))
b = np.ones((10,1))
c = np.memmap('zeros.mat', dtype=np.float64, mode='w+', shape=(10,10), order='C')

a.dot(b.T, out=c)

我得到了:

ValueError:输出数组不可接受(必须具有正确的类型， 尺寸，并成为C数组)

ValueError: output array is not acceptable (must have the right type, nr dimensions, and be a C-Array)

我检查了错误消息中的所有条件，这些条件似乎很合适:

I check all conditions from the error message and they seem to fit:

>>> print(a.dtype == b.dtype == c.dtype)
>>> print(np.dot(a, b.T).shape == c.shape)
>>> print(c.flags['C_CONTIGUOUS'])

True
True
True

当我将c替换为:

c = np.zeros((10,10))

有效.

我在做什么错了?

推荐答案

它不仅需要与dtype相匹配；还可以与dtype相匹配.如type(c)一样，它还必须具有正确的 type . c是numpy.memmap实例，而不是numpy.ndarray，因此检查失败.

It doesn't just have to match the dtype; it also has to have the right type, as in type(c). c is a numpy.memmap instance, not a numpy.ndarray, so that check fails.

如 numpy.memmap文档，您可以改为使用mmap.mmap映射文件并创建由mmap支持的numpy.ndarray作为其缓冲区.您可以查看 numpy.memmap实现看看这样做可能涉及什么.

As recommended in the numpy.memmap docs, you could instead use mmap.mmap to map the file and create a numpy.ndarray backed by the mmap as its buffer. You can look at the numpy.memmap implementation to see what might be involved in doing that.

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