I found one Sionna LDPC decoder bug that causes the code crash when filling bit size is zero in some condition

[hahaliu2001]

recently I tried to use Sionna LDPC decoder and found the issue.

To trigger the LDPC decoder crash:
set k=3840, n = 3840*5, bg =2

The code bug poistion
I went through the code and think that the crash reason is because below code in line 1513 of src/sionna/phy/fec/ldpc/decoding.py
# Remove last CNs and VNs from pcm
pcm = pcm[: -self._nb_pruned_nodes, : -self._nb_pruned_nodes]

The bug reason
when -self._nb_pruned_nodes =0, pcm return empty array which is not expected

The condition to trigger this issue
(1) prune_pcm=True, (2)k_filler=0 (3) nb_punc_bits=0, no puncturing

[SebastianCa]

Hi @hahaliu2001,

this is indeed a bug; it will be fixed in the next version of Sionna. Thanks for reporting the issue.