TypeError: 'NoneType' object is not callable

[xxmlala]

It runs well with the code in 'Quick-start' from https://github.com/idiap/fast-transformers.
But I meet this error when running the 'train.py' with no modification:

name: train_default
args Namespace(batch_size='1', epochs=200, gpus=None, lr=0.0001, name='train_default', path=None, train_data='../dataset/lpd_5_prcem_mix_v8_10000.npz')
num of encoder classes: [  18    3   18  129   18    6   20  102 4865] [7, 1, 6]
D_MODEL 512  N_LAYER 12  N_HEAD 8 DECODER ATTN causal-linear
>>>>>: [  18    3   18  129   18    6   20  102 4865]
DEVICE COUNT: 1
VISIBLE: 0
n_parameters: 39,006,324
    train_data: dataset
    batch_size: 1
    num_batch: 3039
    train_x: (3039, 9999, 9)
    train_y: (3039, 9999, 9)
    train_mask: (3039, 9999)
    lr_init: 0.0001
    DECAY_EPOCH: []
    DECAY_RATIO: 0.1
Traceback (most recent call last):
  File "train.py", line 226, in <module>
    train_dp()
  File "train.py", line 169, in train_dp
    losses = net(is_train=True, x=batch_x, target=batch_y, loss_mask=batch_mask, init_token=batch_init)
  File "/opt/conda/lib/python3.6/site-packages/torch/nn/modules/module.py", line 550, in __call__
    result = self.forward(*input, **kwargs)
  File "/opt/conda/lib/python3.6/site-packages/torch/nn/parallel/data_parallel.py", line 153, in forward
    return self.module(*inputs[0], **kwargs[0])
  File "/opt/conda/lib/python3.6/site-packages/torch/nn/modules/module.py", line 550, in __call__
    result = self.forward(*input, **kwargs)
  File "/home/jovyan/work/test-mm21/video-bgm-generation/src/model.py", line 482, in forward
    return self.train_forward(**kwargs)
  File "/home/jovyan/work/test-mm21/video-bgm-generation/src/model.py", line 450, in train_forward
    h, y_type = self.forward_hidden(x, memory=None, is_training=True, init_token=init_token)
  File "/home/jovyan/work/test-mm21/video-bgm-generation/src/model.py", line 221, in forward_hidden
    encoder_hidden = self.transformer_encoder(encoder_pos_emb, attn_mask)
  File "/opt/conda/lib/python3.6/site-packages/torch/nn/modules/module.py", line 550, in __call__
    result = self.forward(*input, **kwargs)
  File "/opt/conda/lib/python3.6/site-packages/fast_transformers/transformers.py", line 138, in forward
    x = layer(x, attn_mask=attn_mask, length_mask=length_mask)
  File "/opt/conda/lib/python3.6/site-packages/torch/nn/modules/module.py", line 550, in __call__
    result = self.forward(*input, **kwargs)
  File "/opt/conda/lib/python3.6/site-packages/fast_transformers/transformers.py", line 81, in forward
    key_lengths=length_mask
  File "/opt/conda/lib/python3.6/site-packages/torch/nn/modules/module.py", line 550, in __call__
    result = self.forward(*input, **kwargs)
  File "/opt/conda/lib/python3.6/site-packages/fast_transformers/attention/attention_layer.py", line 109, in forward
    key_lengths
  File "/opt/conda/lib/python3.6/site-packages/torch/nn/modules/module.py", line 550, in __call__
    result = self.forward(*input, **kwargs)
  File "/opt/conda/lib/python3.6/site-packages/fast_transformers/attention/causal_linear_attention.py", line 101, in forward
    values
  File "/opt/conda/lib/python3.6/site-packages/fast_transformers/attention/causal_linear_attention.py", line 23, in causal_linear
    V_new = causal_dot_product(Q, K, V)
  File "/opt/conda/lib/python3.6/site-packages/fast_transformers/causal_product/__init__.py", line 48, in forward
    product
TypeError: 'NoneType' object is not callable

[wzk1015]

see #3 , you should use correct versions of torch and fast-transformers based on your CUDA version

the Quick-start of the fast-transformer repo uses full attention, but ours use causal-linear, so the Quick-start does not guarantee your environment is correct

[xxmlala]

Thanks for your reply very much!
When I changed my pytorch to the right version, the problem vanished.