Change GradientClipByValue to GradientClipByGlobalNorm in ocr attention model. (#3879)

PaddleCV/ocr_recognition/attention_model.py

@@ -188,7 +188,7 @@ def attention_train_net(args, data_shape, num_classes):
     prediction = gru_decoder_with_attention(trg_embedding, encoded_vector,
                                             encoded_proj, decoder_boot,
                                             decoder_size, num_classes)
-    fluid.clip.set_gradient_clip(fluid.clip.GradientClipByValue(args.gradient_clip))
+    fluid.clip.set_gradient_clip(fluid.clip.GradientClipByGlobalNorm(args.gradient_clip))
     label_out = fluid.layers.cast(x=label_out, dtype='int64')
 
     _, maxid = fluid.layers.topk(input=prediction, k=1)

PaddleCV/ocr_recognition/run_attention.sh

 export CUDA_VISIBLE_DEVICES=0
 nohup python train.py \
 --lr=1.0 \
---gradient_clip=10 \
+--gradient_clip=5.0 \
 --model="attention" \
 --log_period=10 \
 > attention.log 2>&1 &