Pytorch 训练与预测时爆显存(out of memory)的解决方案

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Pytorch 训练时有时候会因为加载的东西过多而爆显存，有些时候这种情况还可以使用cuda的清理技术进行修整。

使用torch.cuda.empty_cache()删除一些不需要的变量代码示例如下：

try:
    output = model(input)
except RuntimeError as exception:
    if "out of memory" in str(exception):
        print("WARNING: out of memory")
        if hasattr(torch.cuda, 'empty_cache'):
            torch.cuda.empty_cache()
    else:
        raise exception

预测的时候爆显存有可能是忘记设置no_grad, 示例代码如下：

with torch.no_grad():
        for _,(inputs,filelist) in tqdm(enumerate(test_loader), desc='predict'):
            if opt.use_gpu:
                inputs = inputs.cuda()
                if len(inputs.shape) < 4:
                    inputs = inputs.unsqueeze(1)
            else:
                if len(inputs.shape) < 4:
                    inputs = torch.transpose(inputs, 1, 2)
                    inputs = inputs.unsqueeze(1)

上述方法都不生效时，试试：

def wipe_memory(self): 
    self._optimizer_to(torch.device('cpu'))
    del self.optimizer
    gc.collect()
    torch.cuda.empty_cache()

def _optimizer_to(self, device):
    for param in self.optimizer.state.values():
        # Not sure there are any global tensors in the state dict
        if isinstance(param, torch.Tensor):
            param.data = param.data.to(device)
            if param._grad is not None:
                param._grad.data = param._grad.data.to(device)
        elif isinstance(param, dict):
            for subparam in param.values():
                if isinstance(subparam, torch.Tensor):
                    subparam.data = subparam.data.to(device)
                    if subparam._grad is not None:
                        subparam._grad.data = subparam._grad.data.to(device)
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