'RuntimeError: No rendezvous handler for env://' with multi-gpu

[costantinoai]

🐛 Bug

I get an error
'RuntimeError: No rendezvous handler for env://'
when I run my model with multiple GPU.

Below the code and the traceback:

trainer = pl.Trainer(gpus = -1,
                     accelerator='ddp',
                     check_val_every_n_epoch=10, 
                    # precision=16,
                    # auto_scale_batch_size='binsearch',
                     callbacks=[checkpoint_callback],
                     max_epochs = 1)

GPU available: True, used: True
TPU available: None, using: 0 TPU cores
LOCAL_RANK: 0 - CUDA_VISIBLE_DEVICES: [0,1]

trainer.fit(model)

initializing ddp: GLOBAL_RANK: 0, MEMBER: 1/2
Traceback (most recent call last):

File "", line 1, in
trainer.fit(model)

File "C:\Users\45027900\Anaconda3\envs\PyTorch\lib\site-packages\pytorch_lightning\trainer\trainer.py", line 470, in fit
results = self.accelerator_backend.train()

File "C:\Users\45027900\Anaconda3\envs\PyTorch\lib\site-packages\pytorch_lightning\accelerators\ddp_accelerator.py", line 152, in train
results = self.ddp_train(process_idx=self.task_idx, model=model)

File "C:\Users\45027900\Anaconda3\envs\PyTorch\lib\site-packages\pytorch_lightning\accelerators\ddp_accelerator.py", line 252, in ddp_train
self.init_ddp_connection(

File "C:\Users\45027900\Anaconda3\envs\PyTorch\lib\site-packages\pytorch_lightning\accelerators\accelerator.py", line 153, in init_ddp_connection
self.ddp_plugin.init_ddp_connection(

File "C:\Users\45027900\Anaconda3\envs\PyTorch\lib\site-packages\pytorch_lightning\plugins\ddp_plugin.py", line 90, in init_ddp_connection
torch_distrib.init_process_group(

File "C:\Users\45027900\Anaconda3\envs\PyTorch\lib\site-packages\torch\distributed\distributed_c10d.py", line 433, in init_process_group
rendezvous_iterator = rendezvous(

File "C:\Users\45027900\Anaconda3\envs\PyTorch\lib\site-packages\torch\distributed\rendezvous.py", line 82, in rendezvous
raise RuntimeError("No rendezvous handler for {}://".format(result.scheme))

RuntimeError: No rendezvous handler for env://

The error is not present if I set

gpus = 1

Expected behavior

Environment

• PyTorch Version (e.g., 1.0): 1.7.1
• OS (e.g., Linux): Windows 10
• How you installed PyTorch (conda, pip, source): conda
• Build command you used (if compiling from source): conda install pytorch torchvision torchaudio cudatoolkit=11.0 -c pytorch
• Python version: 3.8.5
• CUDA/cuDNN version: 11.0
• GPU models and configuration: 2 * Quadro RTX 6000
• Any other relevant information:

[github-actions]

Hi! thanks for your contribution!, great first issue!

[costantinoai]

Also, I don't know if it is related, but when I check the GPU performance during training (with the flag GPU = 1) using windows task manager, I can see only 1-2% used in the GPU, and 45-50% in the CPU. Is this a normal behaviour?

[Borda]

@costantinoai mind share what PL version are you using? also, do you have and full example to reproduce?

[costantinoai]

Hi @Borda ,
Thanks for your reply.

PL version is 1.1.2.

I do have an example of the full code on colab, but I would rather not post it publicly.

How can I share it with you?

[awaelchli]

Hi, you can ping me on slack if you want. It's probably an issue with passing the argument gpus=-1 to the subprocess script. I bet if you set gpus=n where n is the number of gpus, it will work. We just have to support -1 for ddp.

[costantinoai]

Ok, thanks. I’ll try setting n and see what happens. I’ll send you the Colab link on slack if I still have issues. Really appreciated! Get Outlook for iOS<https://aka.ms/o0ukef>

…

________________________________ From: Adrian Wälchli <[email protected]> Sent: Thursday, January 7, 2021 11:37:33 AM To: PyTorchLightning/pytorch-lightning <[email protected]> Cc: Andrea Costantino <[email protected]>; Mention <[email protected]> Subject: Re: [PyTorchLightning/pytorch-lightning] 'RuntimeError: No rendezvous handler for env://' with multi-gpu (#5358) Hi, you can ping me on slack if you want. It's probably an issue with passing the argument gpus=-1 to the script. I bet if you set gpus=n where n is the number of gpus, it will work. We just have to support -1 for ddp. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub<#5358 (comment)>, or unsubscribe<https:/notifications/unsubscribe-auth/AOCXNCMM3CA3OQJSM2ZAP5DSYT643ANCNFSM4VU7DUZQ>.

[costantinoai]

@awaelchli still got the same problem after setting gpus = 2. I reached you on twitter (I don't have a slack account).

Thanks!

[awaelchli]

In summary after private conversation with @costantinoai

• ddp not supported on windows platform (yet)
• script needs guard around entry point (if __name__ == "__main__")

if these requirements are not met, we see the No rendezvous handler for env://' or similar exceptions.

[BlockWaving]

Hi, I also get this error when adding the second gpu to machine:

RuntimeError: No rendezvous handler for env://

please advise how to fix and/or work around?
Thx!

[awaelchli]

RuntimeError: No rendezvous handler for env://

That's not much information, but one possibility is because you are on Windows.
accelerator=ddp will not work on windows, you have to choose dp.

[mdja]

I am on windows and saw this error. change accelerator to 'dp' works.

[DavidRimel]

I am on windows and saw this error. change accelerator to 'dp' works.

Windows 10 user here.. this worked for me

[carlomarxdk]

I am on Pytorch-Lightning 1.2.1. and I still run into the issue on Windows if I set accelerator to "dp". I am training on 1 GPU.
I encounter this issue when I use DeepSpeed plugin.

[awaelchli]

@carlomarxdk is deepspeed supported on windows? I can't find any mention of it, so probably not.

[ibrahimishag]

I ran into this issue on Windows 10.

[ibrahimishag]

Changing the accelerator to dp on Windows 10 as suggested by @awaelchli and @mdja solved my issue.
Thank you.