cupy.mask_indices(n, mask_func, k=0)[source]#

Return the indices to access (n, n) arrays, given a masking function.

Assume mask_func is a function that, for a square array a of size (n, n) with a possible offset argument k, when called as mask_func(a, k) returns a new array with zeros in certain locations (functions like triu() or tril() do precisely this). Then this function returns the indices where the non-zero values would be located.

  • n (int) – The returned indices will be valid to access arrays of shape (n, n).

  • mask_func (callable) – A function whose call signature is similar to that of triu(), tril(). That is, mask_func(x, k) returns a boolean array, shaped like x. k is an optional argument to the function.

  • k (scalar) – An optional argument which is passed through to mask_func. Functions like triu(), tril() take a second argument that is interpreted as an offset.


The n arrays of indices corresponding to the locations where mask_func(np.ones((n, n)), k) is True.

Return type:

tuple of arrays


This function may synchronize the device.