diff --git a/deepspeech/__init__.py b/deepspeech/__init__.py
index 5f9ba007..ca5b4ba5 100644
--- a/deepspeech/__init__.py
+++ b/deepspeech/__init__.py
@@ -233,7 +233,7 @@ def is_broadcastable(shp1, shp2):
 def masked_fill(xs: paddle.Tensor,
                 mask: paddle.Tensor,
                 value: Union[float, int]):
-    assert is_broadcastable(xs.shape, mask.shape) is True
+    assert is_broadcastable(xs.shape, mask.shape) is True, (xs.shape, mask.shape)
     bshape = paddle.broadcast_shape(xs.shape, mask.shape)
     mask = mask.broadcast_to(bshape)
     trues = paddle.ones_like(xs) * value
@@ -312,18 +312,18 @@ if not hasattr(paddle.Tensor, 'type_as'):
 
 
 def to(x: paddle.Tensor, *args, **kwargs) -> paddle.Tensor:
-    assert len(args) == 1
-    if isinstance(args[0], str):  # dtype
-        return x.astype(args[0])
-    elif isinstance(args[0], paddle.Tensor):  #Tensor
-        return x.astype(args[0].dtype)
-    else:  # Device
-        return x
+   assert len(args) == 1
+   if isinstance(args[0], str):  # dtype
+       return x.astype(args[0])
+   elif isinstance(args[0], paddle.Tensor):  # Tensor
+       return x.astype(args[0].dtype)
+   else:  # Device
+       return x
 
 
 if not hasattr(paddle.Tensor, 'to'):
-    logger.debug("register user to to paddle.Tensor, remove this when fixed!")
-    setattr(paddle.Tensor, 'to', to)
+   logger.debug("register user to to paddle.Tensor, remove this when fixed!")
+   setattr(paddle.Tensor, 'to', to)
 
 
 def func_float(x: paddle.Tensor) -> paddle.Tensor:
diff --git a/deepspeech/decoders/beam_search.py b/deepspeech/decoders/beam_search.py
index 5bf0d3e2..afb8aefa 100644
--- a/deepspeech/decoders/beam_search.py
+++ b/deepspeech/decoders/beam_search.py
@@ -1,7 +1,6 @@
 """Beam search module."""
 
 from itertools import chain
-import logger
 from typing import Any
 from typing import Dict
 from typing import List
@@ -141,7 +140,7 @@ class BeamSearch(paddle.nn.Layer):
         ]
 
     @staticmethod
-    def append_token(xs: paddle.Tensor, x: int) -> paddle.Tensor:
+    def append_token(xs: paddle.Tensor, x: Union[int, paddle.Tensor]) -> paddle.Tensor:
         """Append new token to prefix tokens.
 
         Args:
@@ -152,8 +151,8 @@ class BeamSearch(paddle.nn.Layer):
             paddle.Tensor: (T+1,), New tensor contains: xs + [x] with xs.dtype and xs.device
 
         """
-        x = paddle.to_tensor([x], dtype=xs.dtype, place=xs.place)
-        return paddle.cat((xs, x))
+        x = paddle.to_tensor([x], dtype=xs.dtype) if isinstance(x, int) else x
+        return paddle.concat((xs, x))
 
     def score_full(
         self, hyp: Hypothesis, x: paddle.Tensor
@@ -306,7 +305,7 @@ class BeamSearch(paddle.nn.Layer):
         part_ids = paddle.arange(self.n_vocab)  # no pre-beam
         for hyp in running_hyps:
             # scoring
-            weighted_scores = paddle.zeros(self.n_vocab, dtype=x.dtype)
+            weighted_scores = paddle.zeros([self.n_vocab], dtype=x.dtype)
             scores, states = self.score_full(hyp, x)
             for k in self.full_scorers:
                 weighted_scores += self.weights[k] * scores[k]
@@ -410,15 +409,20 @@ class BeamSearch(paddle.nn.Layer):
         best = nbest_hyps[0]
         for k, v in best.scores.items():
             logger.info(
-                f"{v:6.2f} * {self.weights[k]:3} = {v * self.weights[k]:6.2f} for {k}"
+                f"{float(v):6.2f} * {self.weights[k]:3} = {float(v) * self.weights[k]:6.2f} for {k}"
             )
-        logger.info(f"total log probability: {best.score:.2f}")
-        logger.info(f"normalized log probability: {best.score / len(best.yseq):.2f}")
+        logger.info(f"total log probability: {float(best.score):.2f}")
+        logger.info(f"normalized log probability: {float(best.score) / len(best.yseq):.2f}")
         logger.info(f"total number of ended hypotheses: {len(nbest_hyps)}")
         if self.token_list is not None:
+            # logger.info(
+            #     "best hypo: "
+            #     + "".join([self.token_list[x] for x in best.yseq[1:-1]])
+            #     + "\n"
+            # )
             logger.info(
                 "best hypo: "
-                + "".join([self.token_list[x] for x in best.yseq[1:-1]])
+                + "".join([self.token_list[x] for x in best.yseq[1:]])
                 + "\n"
             )
         return nbest_hyps
diff --git a/deepspeech/decoders/recog.py b/deepspeech/decoders/recog.py
index 399c5c54..867569aa 100644
--- a/deepspeech/decoders/recog.py
+++ b/deepspeech/decoders/recog.py
@@ -2,18 +2,22 @@
 
 import json
 import paddle
+import yaml
+from yacs.config import CfgNode
+from pathlib import Path
+import jsonlines
 
 # from espnet.asr.asr_utils import get_model_conf
 # from espnet.asr.asr_utils import torch_load
 # from espnet.asr.pytorch_backend.asr import load_trained_model
 # from espnet.nets.lm_interface import dynamic_import_lm
 
-# from espnet.nets.asr_interface import ASRInterface
+from deepspeech.models.asr_interface import ASRInterface
 
 from .utils import add_results_to_json
 # from .batch_beam_search import BatchBeamSearch
 from .beam_search import BeamSearch
-from .scorer_interface import BatchScorerInterface
+from .scorers.scorer_interface import BatchScorerInterface
 from .scorers.length_bonus import LengthBonus
 
 from deepspeech.io.reader import LoadInputsAndTargets
@@ -21,6 +25,14 @@ from deepspeech.utils.log import Log
 logger = Log(__name__).getlog()
 
 
+from deepspeech.utils.dynamic_import import dynamic_import
+from deepspeech.utils.utility import print_arguments
+
+model_test_alias = {
+    "u2": "deepspeech.exps.u2.model:U2Tester",
+    "u2_kaldi": "deepspeech.exps.u2_kaldi.model:U2Tester",
+}
+
 def recog_v2(args):
     """Decode with custom models that implements ScorerInterface.
 
@@ -36,16 +48,31 @@ def recog_v2(args):
         raise NotImplementedError("streaming mode is not implemented")
     if args.word_rnnlm:
         raise NotImplementedError("word LM is not implemented")
-
+    args.nprocs = args.ngpu
     # set_deterministic(args)
-    model, train_args = load_trained_model(args.model)
-    # assert isinstance(model, ASRInterface)
-    model.eval()
+
+    #model, train_args = load_trained_model(args.model)
+    model_path = Path(args.model)
+    ckpt_dir = model_path.parent.parent
+
+    confs = CfgNode()
+    confs.set_new_allowed(True)
+    confs.merge_from_file(args.model_conf)
+
+    class_obj = dynamic_import(args.model_name, model_test_alias)
+    exp = class_obj(confs, args)
+    with exp.eval():
+        exp.setup()
+        exp.restore()
+    char_list = exp.args.char_list
+
+    model = exp.model
+    assert isinstance(model, ASRInterface)
     load_inputs_and_targets = LoadInputsAndTargets(
         mode="asr",
         load_output=False,
         sort_in_input_length=False,
-        preprocess_conf=train_args.preprocess_conf
+        preprocess_conf=confs.collator.augmentation_config
         if args.preprocess_conf is None
         else args.preprocess_conf,
         preprocess_args={"train": False},
@@ -56,7 +83,7 @@ def recog_v2(args):
         # NOTE: for a compatibility with less than 0.5.0 version models
         lm_model_module = getattr(lm_args, "model_module", "default")
         lm_class = dynamic_import_lm(lm_model_module, lm_args.backend)
-        lm = lm_class(len(train_args.char_list), lm_args)
+        lm = lm_class(len(char_list), lm_args)
         torch_load(args.rnnlm, lm)
         lm.eval()
     else:
@@ -67,16 +94,16 @@ def recog_v2(args):
         from .scorers.ngram import NgramPartScorer
 
         if args.ngram_scorer == "full":
-            ngram = NgramFullScorer(args.ngram_model, train_args.char_list)
+            ngram = NgramFullScorer(args.ngram_model, char_list)
         else:
-            ngram = NgramPartScorer(args.ngram_model, train_args.char_list)
+            ngram = NgramPartScorer(args.ngram_model, char_list)
     else:
         ngram = None
 
     scorers = model.scorers()
     scorers["lm"] = lm
     scorers["ngram"] = ngram
-    scorers["length_bonus"] = LengthBonus(len(train_args.char_list))
+    scorers["length_bonus"] = LengthBonus(len(char_list))
     weights = dict(
         decoder=1.0 - args.ctc_weight,
         ctc=args.ctc_weight,
@@ -86,14 +113,15 @@ def recog_v2(args):
     )
     beam_search = BeamSearch(
         beam_size=args.beam_size,
-        vocab_size=len(train_args.char_list),
+        vocab_size=len(char_list),
         weights=weights,
         scorers=scorers,
         sos=model.sos,
         eos=model.eos,
-        token_list=train_args.char_list,
+        token_list=char_list,
         pre_beam_score_key=None if args.ctc_weight == 1.0 else "full",
     )
+
     # TODO(karita): make all scorers batchfied
     if args.batchsize == 1:
         non_batch = [
@@ -116,6 +144,7 @@ def recog_v2(args):
         device = "gpu:0"
     else:
         device = "cpu"
+    paddle.set_device(device)
     dtype = getattr(paddle, args.dtype)
     logger.info(f"Decoding device={device}, dtype={dtype}")
     model.to(device=device, dtype=dtype)
@@ -124,31 +153,41 @@ def recog_v2(args):
     beam_search.eval()
 
     # read json data
-    with open(args.recog_json, "rb") as f:
-        js = json.load(f)
+    js = []
+    with jsonlines.open(args.recog_json, "r") as reader:
+        for item in reader:
+            js.append(item)
     # josnlines to dict, key by 'utt'
     js = {item['utt']: item for item in js}
 
     new_js = {}
     with paddle.no_grad():
-        for idx, name in enumerate(js.keys(), 1):
-            logger.info("(%d/%d) decoding " + name, idx, len(js.keys()))
-            batch = [(name, js[name])]
-            feat = load_inputs_and_targets(batch)[0][0]
-            enc = model.encode(paddle.to_tensor(feat).to(device=device, dtype=dtype))
-            nbest_hyps = beam_search(
-                x=enc, maxlenratio=args.maxlenratio, minlenratio=args.minlenratio
-            )
-            nbest_hyps = [
-                h.asdict() for h in nbest_hyps[: min(len(nbest_hyps), args.nbest)]
-            ]
-            new_js[name] = add_results_to_json(
-                js[name], nbest_hyps, train_args.char_list
-            )
-
-    with open(args.result_label, "wb") as f:
-        f.write(
-            json.dumps(
-                {"utts": new_js}, indent=4, ensure_ascii=False, sort_keys=True
-            ).encode("utf_8")
-        )
+        with jsonlines.open(args.result_label, "w") as f:
+            for idx, name in enumerate(js.keys(), 1):
+                logger.info(f"({idx}/{len(js.keys())}) decoding " + name)
+                batch = [(name, js[name])]
+                feat = load_inputs_and_targets(batch)[0][0]
+                logger.info(f'feat: {feat.shape}')
+                enc = model.encode(paddle.to_tensor(feat).to(dtype))
+                logger.info(f'eouts: {enc.shape}')
+                nbest_hyps = beam_search(
+                    x=enc, maxlenratio=args.maxlenratio, minlenratio=args.minlenratio
+                )
+                nbest_hyps = [
+                    h.asdict() for h in nbest_hyps[: min(len(nbest_hyps), args.nbest)]
+                ]
+                new_js[name] = add_results_to_json(
+                    js[name], nbest_hyps, char_list
+                )
+
+                item = new_js[name]['output'][0] # 1-best
+                utt = name 
+                ref = item['text']
+                rec_text = item['rec_text'].replace('▁', ' ').replace('<eos>', '').strip()
+                rec_tokenid = map(int, item['rec_tokenid'].split())
+                f.write({
+                        "utt": utt,
+                        "refs": [ref],
+                        "hyps": [rec_text],
+                        "hyps_tokenid": [rec_tokenid],
+                    })
\ No newline at end of file
diff --git a/deepspeech/decoders/scorers/ctc.py b/deepspeech/decoders/scorers/ctc.py
index 36b4bfd3..4871d6e1 100644
--- a/deepspeech/decoders/scorers/ctc.py
+++ b/deepspeech/decoders/scorers/ctc.py
@@ -15,8 +15,8 @@
 import numpy as np
 import paddle
 
-from .ctc_prefix_score import CTCPrefixScorer
-from .ctc_prefix_score import CTCPrefixScorerPD
+from .ctc_prefix_score import CTCPrefixScore
+from .ctc_prefix_score import CTCPrefixScorePD
 from .scorer_interface import BatchPartialScorerInterface
 
 
diff --git a/deepspeech/decoders/scorers/ctc_prefix_score.py b/deepspeech/decoders/scorers/ctc_prefix_score.py
index 5f568c81..c85d546d 100644
--- a/deepspeech/decoders/scorers/ctc_prefix_score.py
+++ b/deepspeech/decoders/scorers/ctc_prefix_score.py
@@ -6,7 +6,7 @@ import paddle
 import six
 
 
-class CTCPrefixScorerPD():
+class CTCPrefixScorePD():
     """Batch processing of CTCPrefixScore
 
     which is based on Algorithm 2 in WATANABE et al.
@@ -267,7 +267,7 @@ class CTCPrefixScorerPD():
             return (r_prev_new, s_prev, f_min_prev, f_max_prev)
 
 
-class CTCPrefixScorer():
+class CTCPrefixScore():
     """Compute CTC label sequence scores
 
     which is based on Algorithm 2 in WATANABE et al.
diff --git a/deepspeech/decoders/scorers/score_interface.py b/deepspeech/decoders/scorers/scorer_interface.py
similarity index 100%
rename from deepspeech/decoders/scorers/score_interface.py
rename to deepspeech/decoders/scorers/scorer_interface.py
diff --git a/deepspeech/decoders/utils.py b/deepspeech/decoders/utils.py
index 0281a78b..f59b55d9 100644
--- a/deepspeech/decoders/utils.py
+++ b/deepspeech/decoders/utils.py
@@ -12,7 +12,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-__all__ = ["end_detect"]
+import numpy as np
+from deepspeech.utils.log import Log
+logger = Log(__name__).getlog()
+
+__all__ = ["end_detect", "parse_hypothesis", "add_results_to_json"]
 
 
 def end_detect(ended_hyps, i, M=3, D_end=np.log(1 * np.exp(-10))):
@@ -118,7 +122,7 @@ def add_results_to_json(js, nbest_hyps, char_list):
         # show 1-best result
         if n == 1:
             if "text" in out_dic.keys():
-                logging.info("groundtruth: %s" % out_dic["text"])
-            logging.info("prediction : %s" % out_dic["rec_text"])
+                logger.info("groundtruth: %s" % out_dic["text"])
+            logger.info("prediction : %s" % out_dic["rec_text"])
 
     return new_js
\ No newline at end of file
diff --git a/deepspeech/exps/u2_kaldi/bin/recog.py b/deepspeech/exps/u2_kaldi/bin/recog.py
new file mode 100644
index 00000000..60f4e58a
--- /dev/null
+++ b/deepspeech/exps/u2_kaldi/bin/recog.py
@@ -0,0 +1,379 @@
+
+"""End-to-end speech recognition model decoding script."""
+
+import configargparse
+import logging
+import os
+import random
+import sys
+
+import numpy as np
+
+from distutils.util import strtobool
+from deepspeech.training.cli import default_argument_parser
+
+# NOTE: you need this func to generate our sphinx doc
+
+def get_parser():
+    """Get default arguments."""
+    parser = configargparse.ArgumentParser(
+        description="Transcribe text from speech using "
+        "a speech recognition model on one CPU or GPU",
+        config_file_parser_class=configargparse.YAMLConfigFileParser,
+        formatter_class=configargparse.ArgumentDefaultsHelpFormatter,
+    )
+    parser.add(
+        '--model-name',
+        type=str,
+        default='u2_kaldi',
+        help='model name, e.g: deepspeech2, u2, u2_kaldi, u2_st')
+    # general configuration
+    parser.add("--config", is_config_file=True, help="Config file path")
+    parser.add(
+        "--config2",
+        is_config_file=True,
+        help="Second config file path that overwrites the settings in `--config`",
+    )
+    parser.add(
+        "--config3",
+        is_config_file=True,
+        help="Third config file path that overwrites the settings "
+        "in `--config` and `--config2`",
+    )
+
+    parser.add_argument("--ngpu", type=int, default=0, help="Number of GPUs")
+    parser.add_argument(
+        "--dtype",
+        choices=("float16", "float32", "float64"),
+        default="float32",
+        help="Float precision (only available in --api v2)",
+    )
+    parser.add_argument("--debugmode", type=int, default=1, help="Debugmode")
+    parser.add_argument("--seed", type=int, default=1, help="Random seed")
+    parser.add_argument("--verbose", "-V", type=int, default=2, help="Verbose option")
+    parser.add_argument(
+        "--batchsize",
+        type=int,
+        default=1,
+        help="Batch size for beam search (0: means no batch processing)",
+    )
+    parser.add_argument(
+        "--preprocess-conf",
+        type=str,
+        default=None,
+        help="The configuration file for the pre-processing",
+    )
+    parser.add_argument(
+        "--api",
+        default="v2",
+        choices=["v2"],
+        help="Beam search APIs "
+        "v2: Experimental API. It supports any models that implements ScorerInterface.",
+    )
+    # task related
+    parser.add_argument(
+        "--recog-json", type=str, help="Filename of recognition data (json)"
+    )
+    parser.add_argument(
+        "--result-label",
+        type=str,
+        required=True,
+        help="Filename of result label data (json)",
+    )
+    # model (parameter) related
+    parser.add_argument(
+        "--model", type=str, required=True, help="Model file parameters to read"
+    )
+    parser.add_argument(
+        "--model-conf", type=str, default=None, help="Model config file"
+    )
+    parser.add_argument(
+        "--num-spkrs",
+        type=int,
+        default=1,
+        choices=[1, 2],
+        help="Number of speakers in the speech",
+    )
+    parser.add_argument(
+        "--num-encs", default=1, type=int, help="Number of encoders in the model."
+    )
+    # search related
+    parser.add_argument("--nbest", type=int, default=1, help="Output N-best hypotheses")
+    parser.add_argument("--beam-size", type=int, default=1, help="Beam size")
+    parser.add_argument("--penalty", type=float, default=0.0, help="Incertion penalty")
+    parser.add_argument(
+        "--maxlenratio",
+        type=float,
+        default=0.0,
+        help="""Input length ratio to obtain max output length.
+                        If maxlenratio=0.0 (default), it uses a end-detect function
+                        to automatically find maximum hypothesis lengths.
+                        If maxlenratio<0.0, its absolute value is interpreted
+                        as a constant max output length""",
+    )
+    parser.add_argument(
+        "--minlenratio",
+        type=float,
+        default=0.0,
+        help="Input length ratio to obtain min output length",
+    )
+    parser.add_argument(
+        "--ctc-weight", type=float, default=0.0, help="CTC weight in joint decoding"
+    )
+    parser.add_argument(
+        "--weights-ctc-dec",
+        type=float,
+        action="append",
+        help="ctc weight assigned to each encoder during decoding."
+        "[in multi-encoder mode only]",
+    )
+    parser.add_argument(
+        "--ctc-window-margin",
+        type=int,
+        default=0,
+        help="""Use CTC window with margin parameter to accelerate
+                        CTC/attention decoding especially on GPU. Smaller magin
+                        makes decoding faster, but may increase search errors.
+                        If margin=0 (default), this function is disabled""",
+    )
+    # transducer related
+    parser.add_argument(
+        "--search-type",
+        type=str,
+        default="default",
+        choices=["default", "nsc", "tsd", "alsd", "maes"],
+        help="""Type of beam search implementation to use during inference.
+        Can be either: default beam search ("default"),
+        N-Step Constrained beam search ("nsc"), Time-Synchronous Decoding ("tsd"),
+        Alignment-Length Synchronous Decoding ("alsd") or
+        modified Adaptive Expansion Search ("maes").""",
+    )
+    parser.add_argument(
+        "--nstep",
+        type=int,
+        default=1,
+        help="""Number of expansion steps allowed in NSC beam search or mAES
+        (nstep > 0 for NSC and nstep > 1 for mAES).""",
+    )
+    parser.add_argument(
+        "--prefix-alpha",
+        type=int,
+        default=2,
+        help="Length prefix difference allowed in NSC beam search or mAES.",
+    )
+    parser.add_argument(
+        "--max-sym-exp",
+        type=int,
+        default=2,
+        help="Number of symbol expansions allowed in TSD.",
+    )
+    parser.add_argument(
+        "--u-max",
+        type=int,
+        default=400,
+        help="Length prefix difference allowed in ALSD.",
+    )
+    parser.add_argument(
+        "--expansion-gamma",
+        type=float,
+        default=2.3,
+        help="Allowed logp difference for prune-by-value method in mAES.",
+    )
+    parser.add_argument(
+        "--expansion-beta",
+        type=int,
+        default=2,
+        help="""Number of additional candidates for expanded hypotheses
+                selection in mAES.""",
+    )
+    parser.add_argument(
+        "--score-norm",
+        type=strtobool,
+        nargs="?",
+        default=True,
+        help="Normalize final hypotheses' score by length",
+    )
+    parser.add_argument(
+        "--softmax-temperature",
+        type=float,
+        default=1.0,
+        help="Penalization term for softmax function.",
+    )
+    # rnnlm related
+    parser.add_argument(
+        "--rnnlm", type=str, default=None, help="RNNLM model file to read"
+    )
+    parser.add_argument(
+        "--rnnlm-conf", type=str, default=None, help="RNNLM model config file to read"
+    )
+    parser.add_argument(
+        "--word-rnnlm", type=str, default=None, help="Word RNNLM model file to read"
+    )
+    parser.add_argument(
+        "--word-rnnlm-conf",
+        type=str,
+        default=None,
+        help="Word RNNLM model config file to read",
+    )
+    parser.add_argument("--word-dict", type=str, default=None, help="Word list to read")
+    parser.add_argument("--lm-weight", type=float, default=0.1, help="RNNLM weight")
+    # ngram related
+    parser.add_argument(
+        "--ngram-model", type=str, default=None, help="ngram model file to read"
+    )
+    parser.add_argument("--ngram-weight", type=float, default=0.1, help="ngram weight")
+    parser.add_argument(
+        "--ngram-scorer",
+        type=str,
+        default="part",
+        choices=("full", "part"),
+        help="""if the ngram is set as a part scorer, similar with CTC scorer,
+                ngram scorer only scores topK hypethesis.
+                if the ngram is set as full scorer, ngram scorer scores all hypthesis
+                the decoding speed of part scorer is musch faster than full one""",
+    )
+    # streaming related
+    parser.add_argument(
+        "--streaming-mode",
+        type=str,
+        default=None,
+        choices=["window", "segment"],
+        help="""Use streaming recognizer for inference.
+                        `--batchsize` must be set to 0 to enable this mode""",
+    )
+    parser.add_argument("--streaming-window", type=int, default=10, help="Window size")
+    parser.add_argument(
+        "--streaming-min-blank-dur",
+        type=int,
+        default=10,
+        help="Minimum blank duration threshold",
+    )
+    parser.add_argument(
+        "--streaming-onset-margin", type=int, default=1, help="Onset margin"
+    )
+    parser.add_argument(
+        "--streaming-offset-margin", type=int, default=1, help="Offset margin"
+    )
+    # non-autoregressive related
+    # Mask CTC related. See https://arxiv.org/abs/2005.08700 for the detail.
+    parser.add_argument(
+        "--maskctc-n-iterations",
+        type=int,
+        default=10,
+        help="Number of decoding iterations."
+        "For Mask CTC, set 0 to predict 1 mask/iter.",
+    )
+    parser.add_argument(
+        "--maskctc-probability-threshold",
+        type=float,
+        default=0.999,
+        help="Threshold probability for CTC output",
+    )
+    # quantize model related
+    parser.add_argument(
+        "--quantize-config",
+        nargs="*",
+        help="Quantize config list. E.g.: --quantize-config=[Linear,LSTM,GRU]",
+    )
+    parser.add_argument(
+        "--quantize-dtype", type=str, default="qint8", help="Dtype dynamic quantize"
+    )
+    parser.add_argument(
+        "--quantize-asr-model",
+        type=bool,
+        default=False,
+        help="Quantize asr model",
+    )
+    parser.add_argument(
+        "--quantize-lm-model",
+        type=bool,
+        default=False,
+        help="Quantize lm model",
+    )
+    return parser
+
+
+def main(args):
+    """Run the main decoding function."""
+    parser = get_parser()
+    parser.add_argument(
+        "--output", metavar="CKPT_DIR", help="path to save checkpoint.")
+    parser.add_argument(
+        "--checkpoint_path", type=str, help="path to load checkpoint")
+    parser.add_argument(
+        "--dict-path", type=str, help="path to load checkpoint")
+    # parser = default_argument_parser(parser)
+    args = parser.parse_args(args)
+
+    if args.ngpu == 0 and args.dtype == "float16":
+        raise ValueError(f"--dtype {args.dtype} does not support the CPU backend.")
+
+    # logging info
+    if args.verbose == 1:
+        logging.basicConfig(
+            level=logging.INFO,
+            format="%(asctime)s (%(module)s:%(lineno)d) %(levelname)s: %(message)s",
+        )
+    elif args.verbose == 2:
+        logging.basicConfig(
+            level=logging.DEBUG,
+            format="%(asctime)s (%(module)s:%(lineno)d) %(levelname)s: %(message)s",
+        )
+    else:
+        logging.basicConfig(
+            level=logging.WARN,
+            format="%(asctime)s (%(module)s:%(lineno)d) %(levelname)s: %(message)s",
+        )
+        logging.warning("Skip DEBUG/INFO messages")
+    logging.info(args)
+
+    # check CUDA_VISIBLE_DEVICES
+    if args.ngpu > 0:
+        cvd = os.environ.get("CUDA_VISIBLE_DEVICES")
+        if cvd is None:
+            logging.warning("CUDA_VISIBLE_DEVICES is not set.")
+        elif args.ngpu != len(cvd.split(",")):
+            logging.error("#gpus is not matched with CUDA_VISIBLE_DEVICES.")
+            sys.exit(1)
+
+        # TODO(mn5k): support of multiple GPUs
+        if args.ngpu > 1:
+            logging.error("The program only supports ngpu=1.")
+            sys.exit(1)
+
+    # display PYTHONPATH
+    logging.info("python path = " + os.environ.get("PYTHONPATH", "(None)"))
+
+    # seed setting
+    random.seed(args.seed)
+    np.random.seed(args.seed)
+    logging.info("set random seed = %d" % args.seed)
+
+    # validate rnn options
+    if args.rnnlm is not None and args.word_rnnlm is not None:
+        logging.error(
+            "It seems that both --rnnlm and --word-rnnlm are specified. "
+            "Please use either option."
+        )
+        sys.exit(1)
+
+    # recog
+    if args.num_spkrs == 1:
+        if args.num_encs == 1:
+            # Experimental API that supports custom LMs
+            if args.api == "v2":
+                from deepspeech.decoders.recog import recog_v2
+                recog_v2(args)
+            else:
+                raise ValueError("Only support --api v2")
+        else:
+            if args.api == "v2":
+                raise NotImplementedError(
+                    f"--num-encs {args.num_encs} > 1 is not supported in --api v2"
+                )
+    elif args.num_spkrs == 2:
+        raise ValueError("asr_mix not supported.")
+
+
+if __name__ == "__main__":
+    main(sys.argv[1:])
diff --git a/deepspeech/exps/u2_kaldi/model.py b/deepspeech/exps/u2_kaldi/model.py
index 18e29b28..3aadca85 100644
--- a/deepspeech/exps/u2_kaldi/model.py
+++ b/deepspeech/exps/u2_kaldi/model.py
@@ -317,11 +317,9 @@ class U2Trainer(Trainer):
         with UpdateConfig(model_conf):
             model_conf.input_dim = self.train_loader.feat_dim
             model_conf.output_dim = self.train_loader.vocab_size
-
         model = U2Model.from_config(model_conf)
         if self.parallel:
             model = paddle.DataParallel(model)
-        logger.info(f"{model}")
         layer_tools.print_params(model, logger.info)
 
         # lr
diff --git a/deepspeech/frontend/featurizer/text_featurizer.py b/deepspeech/frontend/featurizer/text_featurizer.py
index 34220432..18ff411b 100644
--- a/deepspeech/frontend/featurizer/text_featurizer.py
+++ b/deepspeech/frontend/featurizer/text_featurizer.py
@@ -207,7 +207,7 @@ class TextFeaturizer():
         """Load vocabulary from file."""
         vocab_list = load_dict(vocab_filepath, maskctc)
         assert vocab_list is not None
-        logger.info(f"Vocab: {pformat(vocab_list)}")
+        logger.debug(f"Vocab: {pformat(vocab_list)}")
 
         id2token = dict(
             [(idx, token) for (idx, token) in enumerate(vocab_list)])
diff --git a/deepspeech/models/u2/u2.py b/deepspeech/models/u2/u2.py
index 8915cbd7..fa517906 100644
--- a/deepspeech/models/u2/u2.py
+++ b/deepspeech/models/u2/u2.py
@@ -50,7 +50,7 @@ from deepspeech.utils.tensor_utils import th_accuracy
 from deepspeech.utils.utility import log_add
 from deepspeech.utils.utility import UpdateConfig
 from deepspeech.models.asr_interface import ASRInterface
-from deepspeech.decoders.scorers.ctc_prefix_score import CTCPrefixScorer
+from deepspeech.decoders.scorers.ctc import CTCPrefixScorer
 
 __all__ = ["U2Model", "U2InferModel"]
 
diff --git a/deepspeech/modules/decoder.py b/deepspeech/modules/decoder.py
index 154b7390..ee3572ea 100644
--- a/deepspeech/modules/decoder.py
+++ b/deepspeech/modules/decoder.py
@@ -28,7 +28,7 @@ from deepspeech.modules.mask import make_non_pad_mask
 from deepspeech.modules.mask import subsequent_mask
 from deepspeech.modules.mask import make_xs_mask
 from deepspeech.modules.positionwise_feed_forward import PositionwiseFeedForward
-from deepspeech.decoders.scorers.score_interface import BatchScorerInterface
+from deepspeech.decoders.scorers.scorer_interface import BatchScorerInterface
 from deepspeech.utils.log import Log
 
 logger = Log(__name__).getlog()
@@ -191,8 +191,8 @@ class TransformerDecoder(BatchScorerInterface, nn.Layer):
         ys: (ylen,)
         x: (xlen, n_feat)
         """
-        ys_mask = subsequent_mask(len(ys)).unsqueeze(0)
-        x_mask = make_xs_mask(x.unsqueeze(0))
+        ys_mask = subsequent_mask(len(ys)).unsqueeze(0) # (B,L,L)
+        x_mask = make_xs_mask(x.unsqueeze(0)).unsqueeze(1) # (B,1,T)
         if self.selfattention_layer_type != "selfattn":
             # TODO(karita): implement cache
             logging.warning(
@@ -237,9 +237,8 @@ class TransformerDecoder(BatchScorerInterface, nn.Layer):
             ]
 
         # batch decoding
-        ys_mask = subsequent_mask(ys.size(-1)).unsqueeze(0)
-
-        xs_mask = make_xs_mask(xs)
+        ys_mask = subsequent_mask(ys.size(-1)).unsqueeze(0) # (B,L,L)
+        xs_mask = make_xs_mask(xs).unsqueeze(1) # (B,1,T)
         logp, states = self.forward_one_step(xs, xs_mask, ys, ys_mask, cache=batch_state)
 
         # transpose state of [layer, batch] into [batch, layer]
diff --git a/deepspeech/modules/mask.py b/deepspeech/modules/mask.py
index cffa10a7..7ae418c0 100644
--- a/deepspeech/modules/mask.py
+++ b/deepspeech/modules/mask.py
@@ -24,15 +24,16 @@ __all__ = [
 ]
 
 
-def make_xs_mask(xs:paddle.Tensor) -> paddle.Tensor:
+def make_xs_mask(xs:paddle.Tensor, pad_value=0.0) -> paddle.Tensor:
     """Maks mask tensor containing indices of non-padded part.
     Args:
         xs (paddle.Tensor): (B, T, D), zeros for pad.
     Returns:
-        paddle.Tensor: Mask Tensor indices of non-padded part. (B, T, D)
+        paddle.Tensor: Mask Tensor indices of non-padded part. (B, T)
     """
-    pad_frame = paddle.zeros([1, 1, xs.shape[-1]], dtype=xs.dtype)
+    pad_frame = paddle.full([1, 1, xs.shape[-1]], pad_value, dtype=xs.dtype)
     mask = xs != pad_frame
+    mask = mask.all(axis=-1)
     return mask
 
 
diff --git a/deepspeech/training/cli.py b/deepspeech/training/cli.py
index ca9652e3..db7076d3 100644
--- a/deepspeech/training/cli.py
+++ b/deepspeech/training/cli.py
@@ -35,7 +35,7 @@ class LoadFromFile(argparse.Action):
             parser.parse_args(f.read().split(), namespace)
 
 
-def default_argument_parser():
+def default_argument_parser(parser=None):
     r"""A simple yet genral argument parser for experiments with parakeet.
 
     This is used in examples with parakeet. And it is intended to be used by
@@ -62,7 +62,9 @@ def default_argument_parser():
     argparse.ArgumentParser
         the parser
     """
-    parser = argparse.ArgumentParser()
+    if parser is None:
+        parser = argparse.ArgumentParser()
+        
     parser.register('action', 'extend', ExtendAction)
     parser.add_argument(
         '--conf', type=open, action=LoadFromFile, help="config file.")
diff --git a/deepspeech/training/trainer.py b/deepspeech/training/trainer.py
index 6c18fa36..b2ee7a1b 100644
--- a/deepspeech/training/trainer.py
+++ b/deepspeech/training/trainer.py
@@ -126,7 +126,7 @@ class Trainer():
             logger.info(f"Set seed {args.seed}")
 
         # profiler and benchmark options
-        if self.args.benchmark_batch_size:
+        if hasattr(self.args, "benchmark_batch_size") and self.args.benchmark_batch_size:
             with UpdateConfig(self.config):
                 self.config.collator.batch_size = self.args.benchmark_batch_size
                 self.config.training.log_interval = 1
@@ -326,12 +326,25 @@ class Trainer():
         finally:
             self.destory()
 
+    def restore(self):
+        """Resume from latest checkpoint at checkpoints in the output
+        directory or load a specified checkpoint.
+
+        If ``args.checkpoint_path`` is not None, load the checkpoint, else
+        resume training.
+        """
+        assert self.args.checkpoint_path
+        infos = self.checkpoint.load_latest_parameters(
+            self.model,
+            checkpoint_path=self.args.checkpoint_path)
+        return infos
+
     def run_test(self):
         """Do Test/Decode"""
         try:
             with Timer("Test/Decode Done: {}"):
                 with self.eval():
-                    self.resume_or_scratch()
+                    self.restore()
                     self.test()
         except KeyboardInterrupt:
             exit(-1)
@@ -341,6 +354,7 @@ class Trainer():
         try:
             with Timer("Export Done: {}"):
                 with self.eval():
+                    self.restore()
                     self.export()
         except KeyboardInterrupt:
             exit(-1)
@@ -350,7 +364,7 @@ class Trainer():
         try:
             with Timer("Align Done: {}"):
                 with self.eval():
-                    self.resume_or_scratch()
+                    self.restore()
                     self.align()
         except KeyboardInterrupt:
             sys.exit(-1)
diff --git a/examples/librispeech/s2/README.md b/examples/librispeech/s2/README.md
index 1f7c6919..6e41cc37 100644
--- a/examples/librispeech/s2/README.md
+++ b/examples/librispeech/s2/README.md
@@ -11,3 +11,4 @@
 | test-clean | ctc_greedy_search | 2620 | 52576 | 95.9 | 3.7 | 0.4 | 0.5 | 4.6 | 48.0 |   
 | test-clean | ctc_prefix_beamsearch | 2620 | 52576 | 95.9 | 3.7 | 0.4 | 0.5 | 4.6 | 47.6 |   
 | test-clean | attention_rescore | 2620 | 52576 | 96.8 | 2.9 | 0.3 | 0.4 | 3.7 | 38.0 |   
+| test-clean | join_ctc_w/o_lm | 2620 | 52576 | 97.2 | 2.6 | 0.3 | 0.4 | 3.2 | 34.9 |   
diff --git a/examples/librispeech/s2/conf/decode/decode.yaml b/examples/librispeech/s2/conf/decode/decode.yaml
new file mode 100644
index 00000000..867bf611
--- /dev/null
+++ b/examples/librispeech/s2/conf/decode/decode.yaml
@@ -0,0 +1,7 @@
+batchsize: 0
+beam-size: 60
+ctc-weight: 0.4
+lm-weight: 0.0
+maxlenratio: 0.0
+minlenratio: 0.0
+penalty: 0.0
diff --git a/examples/librispeech/s2/conf/decode/decode_all.yaml b/examples/librispeech/s2/conf/decode/decode_all.yaml
new file mode 100644
index 00000000..87d5f6d1
--- /dev/null
+++ b/examples/librispeech/s2/conf/decode/decode_all.yaml
@@ -0,0 +1,7 @@
+batchsize: 0
+beam-size: 60
+ctc-weight: 0.4
+lm-weight: 0.6
+maxlenratio: 0.0
+minlenratio: 0.0
+penalty: 0.0
\ No newline at end of file
diff --git a/examples/librispeech/s2/conf/decode/decode_wo_lm.yaml b/examples/librispeech/s2/conf/decode/decode_wo_lm.yaml
new file mode 100644
index 00000000..a82dba23
--- /dev/null
+++ b/examples/librispeech/s2/conf/decode/decode_wo_lm.yaml
@@ -0,0 +1,7 @@
+batchsize: 0
+beam-size: 60
+ctc-weight: 0.4
+lm-weight: 0.0
+maxlenratio: 0.0
+minlenratio: 0.0
+penalty: 0.0
\ No newline at end of file
diff --git a/examples/librispeech/s2/local/recog.sh b/examples/librispeech/s2/local/recog.sh
new file mode 100755
index 00000000..0393535b
--- /dev/null
+++ b/examples/librispeech/s2/local/recog.sh
@@ -0,0 +1,103 @@
+#!/bin/bash
+
+set -e
+
+expdir=exp
+datadir=data
+nj=32
+
+decode_config=conf/decode/decode.yaml
+lang_model=rnnlm.model.best
+lmexpdir=exp/train_rnnlm_pytorch_lm_transformer_cosine_batchsize32_lr1e-4_layer16_unigram5000_ngpu4/
+
+lmtag='nolm'
+
+recog_set="test-clean test-other dev-clean dev-other"
+recog_set="test-clean"
+
+# bpemode (unigram or bpe)
+nbpe=5000
+bpemode=unigram
+bpeprefix="data/bpe_${bpemode}_${nbpe}"
+bpemodel=${bpeprefix}.model
+
+if [ $# != 3 ];then
+    echo "usage: ${0} config_path dict_path ckpt_path_prefix"
+    exit -1
+fi
+
+ngpu=$(echo $CUDA_VISIBLE_DEVICES | awk -F "," '{print NF}')
+echo "using $ngpu gpus..."
+
+config_path=$1
+dict=$2
+ckpt_prefix=$3
+
+ckpt_dir=$(dirname `dirname ${ckpt_prefix}`)
+echo "ckpt dir: ${ckpt_dir}"
+
+ckpt_tag=$(basename ${ckpt_prefix})
+echo "ckpt tag: ${ckpt_tag}"
+
+chunk_mode=false
+if [[ ${config_path} =~ ^.*chunk_.*yaml$ ]];then
+    chunk_mode=true
+fi
+echo "chunk mode: ${chunk_mode}"
+echo "decode conf: ${decode_config}"
+
+# download language model
+#bash local/download_lm_en.sh
+#if [ $? -ne 0 ]; then
+#    exit 1
+#fi
+
+
+pids=() # initialize pids
+
+for dmethd in join_ctc; do
+(
+    echo "${dmethd} decoding"
+    for rtask in ${recog_set}; do
+    (
+        echo "${rtask} dataset"
+        decode_dir=${ckpt_dir}/decode/decode_${rtask/-/_}_${dmethd}_$(basename ${config_path%.*})_${lmtag}_${ckpt_tag}
+        feat_recog_dir=${datadir}
+        mkdir -p ${decode_dir}
+        mkdir -p ${feat_recog_dir}
+
+        # split data
+        split_json.sh manifest.${rtask} ${nj}
+
+        #### use CPU for decoding
+        ngpu=0
+
+        # set batchsize 0 to disable batch decoding
+        ${decode_cmd} JOB=1:${nj} ${decode_dir}/log/decode.JOB.log \
+            python3 -u ${BIN_DIR}/recog.py \
+                --api v2 \
+                --config ${decode_config} \
+                --ngpu ${ngpu} \
+                --batchsize 0 \
+                --checkpoint_path ${ckpt_prefix} \
+                --dict-path ${dict} \
+                --recog-json ${feat_recog_dir}/split${nj}/JOB/manifest.${rtask} \
+                --result-label ${decode_dir}/data.JOB.json \
+                --model-conf ${config_path} \
+                --model ${ckpt_prefix}.pdparams
+
+                #--rnnlm ${lmexpdir}/${lang_model} \
+
+        score_sclite.sh --bpe ${nbpe} --bpemodel ${bpemodel} --wer false ${decode_dir} ${dict}
+
+    ) &
+    pids+=($!) # store background pids
+    i=0; for pid in "${pids[@]}"; do wait ${pid} || ((++i)); done
+    [ ${i} -gt 0 ] && echo "$0: ${i} background jobs are failed." || true
+    done
+)
+done
+
+echo "Finished"
+
+exit 0
diff --git a/examples/librispeech/s2/local/test.sh b/examples/librispeech/s2/local/test.sh
index a6b6cfa9..006a13c5 100755
--- a/examples/librispeech/s2/local/test.sh
+++ b/examples/librispeech/s2/local/test.sh
@@ -83,7 +83,7 @@ for dmethd in attention ctc_greedy_search ctc_prefix_beam_search attention_resco
             --opts decoding.batch_size ${batch_size} \
             --opts data.test_manifest ${feat_recog_dir}/split${nj}/JOB/manifest.${rtask}
 
-        score_sclite.sh --bpe ${nbpe} --bpemodel ${bpemodel} --wer false ${expdir}/${decode_dir} ${dict}
+        score_sclite.sh --bpe ${nbpe} --bpemodel ${bpemodel} --wer false ${decode_dir} ${dict}
 
     ) &
     pids+=($!) # store background pids
diff --git a/requirements.txt b/requirements.txt
index 2a3f0651..42fd645a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -40,3 +40,4 @@ pyworld
 jieba
 phkit
 yq
+ConfigArgParse
\ No newline at end of file