ndarray 1D matrix multiplication #397

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derppening · 2024-04-23T10:31:12+08:00

derppening commented

2024-04-23 10:31:12 +08:00

The behavior depends on the arguments in the following way.

...

If the first argument is 1-D, it is promoted to a matrix by prepending a 1 to its dimensions. After matrix multiplication the prepended 1 is removed.

If the second argument is 1-D, it is promoted to a matrix by appending a 1 to its dimensions. After matrix multiplication the appended 1 is removed.

>>> np.identity(2) @ np.zeros((2))
array([0., 0.])
>>> np.zeros((2)) @ np.identity(2)
array([0., 0.])
>>> np.zeros((2)) @ np.zeros(2)
0.0

> The behavior depends on the arguments in the following way. > > ... > > - If the first argument is 1-D, it is promoted to a matrix by prepending a 1 to its dimensions. After matrix multiplication the prepended 1 is removed. > > - If the second argument is 1-D, it is promoted to a matrix by appending a 1 to its dimensions. After matrix multiplication the appended 1 is removed. ```py >>> np.identity(2) @ np.zeros((2)) array([0., 0.]) >>> np.zeros((2)) @ np.identity(2) array([0., 0.]) >>> np.zeros((2)) @ np.zeros(2) 0.0 ```

derppening referenced this issue

2024-04-23 10:31:31 +08:00

ndarray: Implement 2D-2D matrix multiplication #398

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