RuntimeError：梯度计算所需的变量之一已被就地操作修改
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【中文标题】RuntimeError：梯度计算所需的变量之一已被就地操作修改【英文标题】：RuntimeError: one of the variables needed for gradient computation has been modified by an inplace operation 【发布时间】：2019-12-29 02:21:43 【问题描述】：在 pytorch 模型训练过程中出现此错误：
：[torch.cuda.LongTensor [128, 1]] 版本为 8；而是预期的版本 7。提示：上面的回溯显示了未能计算其梯度的操作。有问题的变量在那里或以后的任何地方都被改变了。祝你好运！
带有堆栈跟踪
sys:1: RuntimeWarning: Traceback of forward call that caused the error:
File "/home/arash/anaconda2/envs/mzh27/lib/python2.7/runpy.py", line 174, in _run_module_as_main
"__main__", fname, loader, pkg_name)
File "/home/arash/anaconda2/envs/mzh27/lib/python2.7/runpy.py", line 72, in _run_code
exec code in run_globals
File "/home/arash/anaconda2/envs/mzh27/lib/python2.7/site-packages/ipykernel_launcher.py", line 16, in <module>
app.launch_new_instance()
File "/home/arash/anaconda2/envs/mzh27/lib/python2.7/site-packages/traitlets/config/application.py", line 658, in launch_instance
app.start()
File "/home/arash/anaconda2/envs/mzh27/lib/python2.7/site-packages/ipykernel/kernelapp.py", line 499, in start
self.io_loop.start()
File "/home/arash/anaconda2/envs/mzh27/lib/python2.7/site-packages/tornado/ioloop.py", line 1073, in start
handler_func(fd_obj, events)
File "/home/arash/anaconda2/envs/mzh27/lib/python2.7/site-packages/tornado/stack_context.py", line 300, in null_wrapper
return fn(*args, **kwargs)
File "/home/arash/.local/lib/python2.7/site-packages/zmq/eventloop/zmqstream.py", line 456, in _handle_events
self._handle_recv()
File "/home/arash/.local/lib/python2.7/site-packages/zmq/eventloop/zmqstream.py", line 486, in _handle_recv
self._run_callback(callback, msg)
File "/home/arash/.local/lib/python2.7/site-packages/zmq/eventloop/zmqstream.py", line 438, in _run_callback
callback(*args, **kwargs)
File "/home/arash/anaconda2/envs/mzh27/lib/python2.7/site-packages/tornado/stack_context.py", line 300, in null_wrapper
return fn(*args, **kwargs)
File "/home/arash/anaconda2/envs/mzh27/lib/python2.7/site-packages/ipykernel/kernelbase.py", line 283, in dispatcher
return self.dispatch_shell(stream, msg)
File "/home/arash/anaconda2/envs/mzh27/lib/python2.7/site-packages/ipykernel/kernelbase.py", line 233, in dispatch_shell
handler(stream, idents, msg)
File "/home/arash/anaconda2/envs/mzh27/lib/python2.7/site-packages/ipykernel/kernelbase.py", line 399, in execute_request
user_expressions, allow_stdin)
File "/home/arash/anaconda2/envs/mzh27/lib/python2.7/site-packages/ipykernel/ipkernel.py", line 208, in do_execute
res = shell.run_cell(code, store_history=store_history, silent=silent)
File "/home/arash/anaconda2/envs/mzh27/lib/python2.7/site-packages/ipykernel/zmqshell.py", line 537, in run_cell
return super(ZMQInteractiveShell, self).run_cell(*args, **kwargs)
File "/home/arash/anaconda2/envs/mzh27/lib/python2.7/site-packages/IPython/core/interactiveshell.py", line 2714, in run_cell
interactivity=interactivity, compiler=compiler, result=result)
File "/home/arash/anaconda2/envs/mzh27/lib/python2.7/site-packages/IPython/core/interactiveshell.py", line 2818, in run_ast_nodes
if self.run_code(code, result):
File "/home/arash/anaconda2/envs/mzh27/lib/python2.7/site-packages/IPython/core/interactiveshell.py", line 2878, in run_code
exec(code_obj, self.user_global_ns, self.user_ns)
File "<ipython-input-71-a5b255596e11>", line 33, in <module>
sampled_captions, sampled_log_probs=predict_captions(out_enc,hid_enc,enc_pp,'sample')
File "<ipython-input-70-a6ea511f0678>", line 18, in predict_captions
out_dec, hid_dec, word_logits = dec.forward(r, last_enc, img_features)
File "<ipython-input-21-0601dad4805f>", line 21, in forward
emb = self.embedding(input)
File "/home/arash/.local/lib/python2.7/site-packages/torch/nn/modules/module.py", line 493, in __call__
result = self.forward(*input, **kwargs)
File "/home/arash/.local/lib/python2.7/site-packages/torch/nn/modules/sparse.py", line 117, in forward
self.norm_type, self.scale_grad_by_freq, self.sparse)
File "/home/arash/.local/lib/python2.7/site-packages/torch/nn/functional.py", line 1506, in embedding
return torch.embedding(weight, input, padding_idx, scale_grad_by_freq, sparse)
---------------------------------------------------------------------------
RuntimeError Traceback (most recent call last)
<ipython-input-71-a5b255596e11> in <module>()
54 torch.stack(sampled_log_probs).reshape(-1)).mean()
55 torch.autograd.set_detect_anomaly(True)
---> 56 loss.backward()
57 clip_grad_value_(enc_optim.param_groups[0]['params'], 5.0)
58 clip_grad_value_(dec_optim.param_groups[0]['params'], 5.0)
/home/arash/.local/lib/python2.7/site-packages/torch/tensor.pyc in backward(self, gradient, retain_graph, create_graph)
105 products. Defaults to ``False``.
106 """
--> 107 torch.autograd.backward(self, gradient, retain_graph, create_graph)
108
109 def register_hook(self, hook):
/home/arash/.local/lib/python2.7/site-packages/torch/autograd/__init__.pyc in backward(tensors, grad_tensors, retain_graph, create_graph, grad_variables)
91 Variable._execution_engine.run_backward(
92 tensors, grad_tensors, retain_graph, create_graph,
---> 93 allow_unreachable=True) # allow_unreachable flag
94
95
但我无法找到导致错误的就地操作。 这是我的代码：
for epoch in xrange(0, 13):
print ("Starting New Epoch: %d" % epoch)
rewards =
'sample_cider': [],
'sample_context': [],
'sample_reward': [], # actual reward, controlled by beta
'greedy_cider': [],
'greedy_context': [],
'greedy_reward': []
order = np.arange(enc_padded_text.shape[0])
np.random.shuffle(order)
enc_padded_text = enc_padded_text[order]
input_text=[input_text[i] for i in order]
dec_text_tensor.data = dec_text_tensor.data[order]
for i in xrange(num_batches):
s = i * BATCH_SIZE
e = (i+1) * BATCH_SIZE
_, enc_pp, dec_pp, enc_lengths = make_packpadded_s2s(s, e, enc_padded_text, dec_text_tensor)
enc.zero_grad()
dec.zero_grad()
hid = enc.initHidden(BATCH_SIZE)
out_enc, hid_enc = enc.forward(enc_pp, hid, enc_lengths)
hid_enc = torch.cat([hid_enc[0,:, :], hid_enc[1,:,:]], dim=1).unsqueeze(0)
gt_dict = dict(zip(_,input_text[s:e]))
sampled_captions, sampled_log_probs=predict_captions(out_enc,hid_enc,enc_pp,'sample')
sampled_dict = dict(zip(_, sampled_captions))
with torch.no_grad():
greedy_captions = predict_captions(out_enc,hid_enc,enc_pp, 'greedy')
greedy_dict = dict(zip(_, greedy_captions))
sample_cider_score, sample_context_score, sample_reward = get_scores(
dec_pp[:,1:], sampled_captions, gt_dict, sampled_dict)
greedy_cider_score, greedy_context_score, greedy_reward = get_scores(
dec_pp[:,1:], greedy_captions, gt_dict, greedy_dict)
# self-critical: score from sampling - score from test time
advantages = torch.Tensor((sample_cider_score - greedy_cider_score).reshape(-1))
# normalize advantages
advantages = ((advantages - advantages.mean()) /
advantages.std() + 1e-9)
if cuda:
advantages = advantages.cuda()
loss = -(advantages *
torch.stack(sampled_log_probs).reshape(-1)).mean()
torch.autograd.set_detect_anomaly(True)
loss.backward()
clip_grad_value_(enc_optim.param_groups[0]['params'], 5.0)
clip_grad_value_(dec_optim.param_groups[0]['params'], 5.0)
enc_optim.step()
dec_optim.step()
rewards['sample_cider'].extend(sample_cider_score)
rewards['sample_context'].extend(sample_context_score)
rewards['sample_reward'].extend(sample_reward)
rewards['greedy_cider'].extend(greedy_cider_score)
rewards['greedy_context'].extend(greedy_context_score)
rewards['greedy_reward'].extend(greedy_reward)
if (b + 1) % 100 == 0:
print('\t[Batch running metrics] - R train :.2f - R train (greedy): :.2f'.format(
b + 1, np.mean(rewards['sample_reward']), np.mean(rewards['greedy_reward'])))
predict_captions 函数：
def predict_captions(img_features,hid_enc,enc_pp, mode='sample', constrain=False,L=22):
dec_tensor = torch.ones((enc_pp.shape[0]), L+1, dtype=torch.long) * Toks.SOS
global cuda
if cuda:
dec_tensor = dec_tensor.cuda(device=device)
last_enc = hid_enc
if mode == 'beam_search':
return self.beam_search(img_features, state, lstm_states)
predictions = []
log_probs = []
# this should store the index of the first occurrence of <EOS>
# for each sample in the batch
EOS_tracker = np.full(img_features.shape[0], None)
for i in range(L):
r=dec_tensor[:,i].unsqueeze(1)
out_dec, hid_dec, word_logits = dec.forward(r, last_enc, img_features)
out_dec[:, 0, Toks.UNK] = -np.inf # ignore unknowns
l=out_dec[:,0]
chosen = torch.argmax(l,dim=1)
dec_tensor[:, i+1] = chosen
last_enc = hid_dec
# decoding stuff
probs = F.softmax(word_logits, dim=2)
probs=probs.reshape(128,20004)
if constrain:
# enforce constraint that the same word can't be predicted
# twice in a row. zero-out the probability of previous words
for p, prev_idx in zip(probs, state['prev_word_indeces']):
p[prev_idx] = 0
if mode == 'sample':
idxs = torch.multinomial(probs, 1)
else:
idxs = torch.argmax(probs, dim=1)
if cuda:
idxs = idxs.cpu()
words = [dec_idx_to_word[index] for index in idxs]
predictions.append(np.array(words).reshape(-1))
# get the respective log probability of chosen word
# for each sample in the batch
log_probs.append([lp[i] for (lp, i)
in zip(torch.log(probs), idxs)])
# inefficient but this should be fast enough anyway... ? :(
eos_idxs = (np.array(words)==dec_idx_to_word[2]).nonzero()[0]
for idx in eos_idxs:
if EOS_tracker[idx] is None:
EOS_tracker[idx] = i + 1
# finish loop if they're all done
if len(EOS_tracker[EOS_tracker == None])==0:
break
# build the actual sentences, up until the first occurrence of <EOS>
captions = [
[' '.join(w[:eos_idx])] for (w, eos_idx) in
zip(np.array(predictions).T, EOS_tracker)
]
print captions
# do this only when training. not needed otherwise.
if mode == 'sample':
log_probs = [lp[:eos_idx].sum() for (lp, eos_idx) in zip(np.array(log_probs).T, EOS_tracker)]
return captions, log_probs
return captions
型号：
class Encoder_s2s(nn.Module):
def __init__(self, input_size, hidden_size):
super(Encoder_s2s, self).__init__()
assert hidden_size % 2 == 0
self.hidden_size = hidden_size
self.input_size = input_size
self.hidden_init_tensor = torch.zeros(2, 1, self.hidden_size/2, requires_grad=True)
nn.init.normal_(self.hidden_init_tensor, mean=0, std=0.05)
self.hidden_init = torch.nn.Parameter(self.hidden_init_tensor, requires_grad=True)
self.embedding = nn.Embedding(input_size, hidden_size)
self.emb_drop = nn.Dropout(0.2)
self.gru = nn.GRU(hidden_size, hidden_size/2, batch_first=True, bidirectional=True)
self.gru_out_drop = nn.Dropout(0.2)
self.gru_hid_drop = nn.Dropout(0.3)
def forward(self, input, hidden, lengths):
emb = self.emb_drop(self.embedding(input))
#emb = embedded_dropout(self.embedding, input, dropout=0.2 if self.training else 0)
pp = torch.nn.utils.rnn.pack_padded_sequence(emb, lengths, batch_first=True)
out, hidden = self.gru(pp, hidden)
out = torch.nn.utils.rnn.pad_packed_sequence(out, batch_first=True)[0]
out = self.gru_out_drop(out)
hidden = self.gru_hid_drop(hidden)
return out, hidden
def initHidden(self, bs):
return self.hidden_init.expand(2, bs, self.hidden_size/2).contiguous()
class DecoderAttn(nn.Module):
def __init__(self, input_size, hidden_size, output_size, out_bias):
super(DecoderAttn, self).__init__()
self.hidden_size = hidden_size
self.input_size = input_size
self.embedding = nn.Embedding(input_size, hidden_size)
self.emb_drop = nn.Dropout(0.2)
self.gru = nn.GRU(hidden_size, hidden_size, batch_first=True)
self.gru_drop = nn.Dropout(0.2)
self.mlp = nn.Linear(hidden_size*2, output_size)
if out_bias is not None:
out_bias_tensor = torch.tensor(out_bias, requires_grad=False)
self.mlp.bias.data[:] = out_bias_tensor
self.logsoftmax = nn.LogSoftmax(dim=2)
self.att_mlp = nn.Linear(hidden_size, hidden_size, bias=False)
self.attn_softmax = nn.Softmax(dim=2)
def forward(self, input, hidden, encoder_outs):
emb = self.embedding(input)
emb=self.emb_drop(emb)
out, hidden = self.gru(emb, hidden)
out_proj = self.att_mlp(out)
enc_out_perm = encoder_outs.permute(0, 2, 1)
e_exp = torch.bmm(out_proj, enc_out_perm)
attn = self.attn_softmax(e_exp)
ctx = torch.bmm(attn, encoder_outs)
full_ctx = torch.cat([self.gru_drop(out), ctx], dim=2)
out = self.mlp(full_ctx)
out1 = self.logsoftmax(out)
return out1, hidden, out
【问题讨论】：
不确定错误的确切位置，但您不应该直接调用enc.forward(enc_pp, hid, enc_lengths)。而是使用 enc(enc_pp, hid, enc_lengths)，因为 pytorch 的 nn.Module 在调用转发之前可能需要做一些事情（例如，使用 DataParallel 时）。
self.mlp.bias.data[:] = out_bias_tensor 似乎是您问题的罪魁祸首。您可以尝试self.mlp.bias.copy_(out_bias_tensor)，但您必须小心，因为这些类型的操作可能会破坏 autograd。
恐怕你的建议不起作用@jodag
只是一个猜测，但可能是DecoderAttn::forward 方法中的out, hidden = self.gru(emb, hidden)，可以在重新分配变量时尝试重命名hidden 变量。
@Minato 没有。这也不起作用
【参考方案1】：
与此描述 torch.cuda.LongTensor [128, 1] 匹配的张量应该会缩小您的搜索范围。
通过 google 快速搜索发现，LongTensors 最常由 min、max、sort 返回。所以线条
l=out_dec[:,0]
chosen = torch.argmax(l,dim=1)
dec_tensor[:, i+1] = chosen
dec_tensor[:, i+1] = chosen 这行很可能有问题。
【讨论】：
【参考方案2】：不确定您是否已经检查过这些，但可以提供帮助：
https://discuss.pytorch.org/t/encounter-the-runtimeerror-one-of-the-variables-needed-for-gradient-computation-has-been-modified-by-an-inplace-operation/836/15
http://www.yongfengli.tk/2018/04/13/inplace-operation-in-pytorch.html
【讨论】：
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