The question states that the input array is of shape (128, 36, 8)
and we are interested in finding unique subarrays of length 8
in the last dimension.
So, I am assuming that the uniqueness is along the first two dimensions being merged together. Let us assume A
as the input 3D array.
Get the number of unique subarrays
# Reshape the 3D array to a 2D array merging the first two dimensions
Ar = A.reshape(-1,A.shape[2])
# Perform lex sort and get the sorted indices and xy pairs
sorted_idx = np.lexsort(Ar.T)
sorted_Ar = Ar[sorted_idx,:]
# Get the count of rows that have at least one TRUE value
# indicating presence of unique subarray there
unq_out = np.any(np.diff(sorted_Ar,axis=0),1).sum()+1
Sample run -
In [159]: A # A is (2,2,3)
Out[159]:
array([[[0, 0, 0],
[0, 0, 2]],
[[0, 0, 2],
[2, 0, 1]]])
In [160]: unq_out
Out[160]: 3
Get the count of occurrences of unique subarrays
# Reshape the 3D array to a 2D array merging the first two dimensions
Ar = A.reshape(-1,A.shape[2])
# Perform lex sort and get the sorted indices and xy pairs
sorted_idx = np.lexsort(Ar.T)
sorted_Ar = Ar[sorted_idx,:]
# Get IDs for each element based on their uniqueness
id = np.append([0],np.any(np.diff(sorted_Ar,axis=0),1).cumsum())
# Get counts for each ID as the final output
unq_count = np.bincount(id)
Sample run -
In [64]: A
Out[64]:
array([[[0, 0, 2],
[1, 1, 1]],
[[1, 1, 1],
[1, 2, 0]]])
In [65]: unq_count
Out[65]: array([1, 2, 1], dtype=int64)