dpnp.triu_indices

dpnp.triu_indices(n, k=0, m=None, device=None, usm_type='device', sycl_queue=None)[source]

Return the indices for the upper-triangle of an (n, m) array.

For full documentation refer to numpy.triu_indices.

Parameters:

  • n (int) -- The size of the arrays for which the returned indices will be valid.

  • k (int, optional) -- Diagonal offset (see dpnp.triu for details). Default: 0.

  • m (int, optional) -- The column dimension of the arrays for which the returned arrays will be valid. By default m is taken equal to n. Default: None.

  • device ({None, string, SyclDevice, SyclQueue}, optional) -- An array API concept of device where the output array is created. The device can be None (the default), an OneAPI filter selector string, an instance of dpctl.SyclDevice corresponding to a non-partitioned SYCL device, an instance of dpctl.SyclQueue, or a Device object returned by dpnp.dpnp_array.dpnp_array.device property.

  • usm_type ({"device", "shared", "host"}, optional) -- The type of SYCL USM allocation for the output array.

  • sycl_queue ({None, SyclQueue}, optional) -- A SYCL queue to use for output array allocation and copying.

Returns:

inds -- The indices for the triangle. The returned tuple contains two arrays, each with the indices along one dimension of the array. Can be used to slice a ndarray of shape(n, n).

Return type:

tuple of dpnp.ndarray

See also

dpnp.tril_indices

similar function, for lower-triangular.

dpnp.mask_indices

generic function accepting an arbitrary mask function.

dpnp.tril

Return lower triangle of an array.

dpnp.triu

Return upper triangle of an array.

Examples

Compute two different sets of indices to access 4x4 arrays, one for the upper triangular part starting at the main diagonal, and one starting two diagonals further right:

>>> import dpnp as np
>>> iu1 = np.triu_indices(4)
>>> iu2 = np.triu_indices(4, 2)

Here is how they can be used with a sample array:

>>> a = np.arange(16).reshape(4, 4)
>>> a
array([[ 0,  1,  2,  3],
       [ 4,  5,  6,  7],
       [ 8,  9, 10, 11],
       [12, 13, 14, 15]])

Both for indexing:

>>> a[iu1]
array([ 0,  1,  2, ..., 10, 11, 15])

And for assigning values:

>>> a[iu1] = -1
>>> a
array([[-1, -1, -1, -1],
       [ 4, -1, -1, -1],
       [ 8,  9, -1, -1],
       [12, 13, 14, -1]])

These cover only a small part of the whole array (two diagonals right of the main one):

>>> a[iu2] = -10
>>> a
array([[ -1,  -1, -10, -10],
       [  4,  -1,  -1, -10],
       [  8,   9,  -1,  -1],
       [ 12,  13,  14,  -1]])