Refactor nbest-oracle.

egs/librispeech/ASR/conformer_ctc/decode.py

@@ -30,14 +30,15 @@ from conformer import Conformer
 
 from icefall.bpe_graph_compiler import BpeCtcTrainingGraphCompiler
 from icefall.checkpoint import average_checkpoints, load_checkpoint
+from icefall.decode import get_lattice
 from icefall.decode import (
-    get_lattice,
     one_best_decoding,
     rescore_with_attention_decoder,
     rescore_with_n_best_list,
     rescore_with_whole_lattice,
+    nbest_oracle,
 )
-from icefall.decode2 import nbest_decoding, nbest_oracle
+from icefall.decode2 import nbest_decoding, nbest_oracle as nbest_oracle2
 from icefall.lexicon import Lexicon
 from icefall.utils import (
     AttributeDict,
@@ -244,7 +245,9 @@ def decode_one_batch(
         # We choose the HLG decoded lattice for speed reasons
         # as HLG decoding is faster and the oracle WER
         # is slightly worse than that of rescored lattices.
-        best_path = nbest_oracle(
+        if True:
+            # TODO: delete the `else` branch
+            best_path = nbest_oracle2(
                 lattice=lattice,
                 num_paths=params.num_paths,
                 ref_texts=supervisions["text"],
@@ -255,6 +258,14 @@ def decode_one_batch(
             hyps = get_texts(best_path)
             hyps = [[word_table[i] for i in ids] for ids in hyps]
             return {"nbest-orcale": hyps}
+        else:
+            return nbest_oracle(
+                lattice=lattice,
+                num_paths=params.num_paths,
+                ref_texts=supervisions["text"],
+                word_table=word_table,
+                scale=params.lattice_score_scale,
+            )
 
     if params.method in ["1best", "nbest"]:
         if params.method == "1best":

icefall/decode.py

@@ -669,7 +669,7 @@ def nbest_oracle(
         word_seq = k2.ragged.index(lattice.aux_labels, path)
     else:
         word_seq = lattice.aux_labels.index(path)
-        word_seq = word_seq.remove_axis(1)
+        word_seq = word_seq.remove_axis(word_seq.num_axes - 2)
 
     word_seq = word_seq.remove_values_leq(0)
     unique_word_seq, _, _ = word_seq.unique(

icefall/decode2.py

@@ -25,7 +25,8 @@ import torch
 from icefall.utils import get_texts
 
 
-# TODO(fangjun): Use Kangwei's C++ implementation that also List[List[int]]
+# TODO(fangjun): Use Kangwei's C++ implementation that also
+# supports List[List[int]]
 def levenshtein_graph(symbol_ids: List[int]) -> k2.Fsa:
     """Construct a graph to compute Levenshtein distance.
 
@@ -42,10 +43,10 @@ def levenshtein_graph(symbol_ids: List[int]) -> k2.Fsa:
     final_state = len(symbol_ids) + 1
     arcs = []
     for i in range(final_state - 1):
-        arcs.append([i, i, 0, 0, -1.01])
+        arcs.append([i, i, 0, 0, -0.5])
+        arcs.append([i, i + 1, 0, symbol_ids[i], -0.5])
         arcs.append([i, i + 1, symbol_ids[i], symbol_ids[i], 0])
-        arcs.append([i, i + 1, 0, symbol_ids[i], -1])
-    arcs.append([final_state - 1, final_state - 1, 0, 0, -1.01])
+    arcs.append([final_state - 1, final_state - 1, 0, 0, -0.5])
     arcs.append([final_state - 1, final_state, -1, -1, 0])
     arcs.append([final_state])
 
@@ -134,7 +135,8 @@ class Nbest(object):
         if isinstance(lattice.aux_labels, torch.Tensor):
             word_seq = k2.ragged.index(lattice.aux_labels, path)
         else:
-            word_seq = lattice.aux_labels.index(path, remove_axis=True)
+            word_seq = lattice.aux_labels.index(path)
+            word_seq = word_seq.remove_axis(word_seq.num_axes - 2)
 
         # Each utterance has `num_paths` paths but some of them transduces
         # to the same word sequence, so we need to remove repeated word
@@ -170,11 +172,11 @@ class Nbest(object):
             # It has 2 axes [arc][word], so aux_labels is also a ragged tensor
             # with 2 axes [arc][word]
             aux_labels, _ = lattice.aux_labels.index(
-                indexes=kept_path.data, axis=0, need_value_indexes=False
+                indexes=kept_path.values, axis=0, need_value_indexes=False
             )
         else:
             assert isinstance(lattice.aux_labels, torch.Tensor)
-            aux_labels = k2.index_select(lattice.aux_labels, kept_path.data)
+            aux_labels = k2.index_select(lattice.aux_labels, kept_path.values)
             # aux_labels is a 1-D torch.Tensor. It also contains -1 and 0.
 
         fsa = k2.linear_fsa(labels)

test/test_decode.py

@@ -40,7 +40,10 @@ def test_nbest_from_lattice():
     lattice = k2.Fsa.from_fsas([lattice, lattice])
 
     nbest = Nbest.from_lattice(
-        lattice=lattice, num_paths=10, use_double_scores=True, scale=0.5
+        lattice=lattice,
+        num_paths=10,
+        use_double_scores=True,
+        lattice_score_scale=0.5,
     )
     # each lattice has only 4 distinct paths that have different word sequences:
     # 10->30