open3d.ml.torch.ops.reduce_subarrays_sum

open3d.ml.torch.ops.reduce_subarrays_sum(values, row_splits)

Computes the sum for each subarray in a flat vector of arrays.

The start and end of the subarrays are defined by an exclusive prefix sum. Zero length subarrays are allowed as shown in the following example:

import open3d.ml.tf as ml3d

ml3d.ops.reduce_subarrays_sum(
    values = [1,2,3,4],
    row_splits=[0,2,2,4] # defines 3 subarrays with starts and ends 0-2,2-2,2-4
    )
# returns [3,0,7]


# or with pytorch
import torch
import open3d.ml.torch as ml3d

ml3d.ops.reduce_subarrays_sum(
  values = torch.Tensor([1,2,3,4]),
  row_splits=torch.LongTensor([0,2,2,4]) # defines 3 subarrays with starts and ends 0-2,2-2,2-4
  )
# returns [3,0,7]

values: Linear memory which stores the values for all arrays.

row_splits: Defines the start and end of each subarray. This is an exclusive

prefix sum with 0 as the first element and the length of values as additional last element. If there are N subarrays the length of this vector is N+1.

sums: The sum of each subarray. The sum of an empty subarray is 0.

sums is a zero length vector if values is a zero length vector.