I don’t fully understand the example, as it seems you would like to “fill” double indices into the second column. However, your index tensor doesn’t contain a 4, so how is the last row created in the output?
Also, what is expected, if e.g. 5 zeros are used in the index tensor? Would the result contain all source values in row0 and what would the output shape be?
EDIT: Also double post from here 2.