fix quant logic (#5806)

* fix quant logic

* fix undef

* fix doc

deploy/slim/quantization/quant.py

@@ -118,6 +118,11 @@ def main(config, device, logger, vdl_writer):
             config['Architecture']["Head"]['out_channels'] = char_num
     model = build_model(config['Architecture'])
 
+    pre_best_model_dict = dict()
+    # load fp32 model to begin quantization
+    if config["Global"]["pretrained_model"] is not None:
+        pre_best_model_dict = load_model(config, model)
+
     quanter = QAT(config=quant_config, act_preprocess=PACT)
     quanter.quantize(model)
 
@@ -134,10 +139,12 @@ def main(config, device, logger, vdl_writer):
         step_each_epoch=len(train_dataloader),
         parameters=model.parameters())
 
+    # resume PACT training process
+    if config["Global"]["checkpoints"] is not None:
+        pre_best_model_dict = load_model(config, model, optimizer)
+
     # build metric
     eval_class = build_metric(config['Metric'])
-    # load pretrain model
-    pre_best_model_dict = load_model(config, model, optimizer)
 
     logger.info('train dataloader has {} iters, valid dataloader has {} iters'.
                 format(len(train_dataloader), len(valid_dataloader)))