Lightning-AI/pytorch-lightning · error · ValueError

You selected an invalid accelerator name: `accelerator={acce

Error message

You selected an invalid accelerator name: `accelerator={accelerator!r}`. Available names are: auto, {', '.join(self._accelerator_types)}.

What it means

AcceleratorConnector validates the `accelerator` argument against the known accelerator types plus 'auto'/'gpu'. Any unknown string (or non-Accelerator object) raises this ValueError listing valid names.

Source

Thrown at src/lightning/pytorch/trainer/connectors/accelerator_connector.py:204

        if isinstance(strategy, str):
            strategy = strategy.lower()

        self._strategy_flag = strategy

        if strategy != "auto" and strategy not in self._registered_strategies and not isinstance(strategy, Strategy):
            raise ValueError(
                f"You selected an invalid strategy name: `strategy={strategy!r}`."
                " It must be either a string or an instance of `lightning.pytorch.strategies.Strategy`."
                " Example choices: auto, ddp, ddp_spawn, deepspeed, ..."
                " Find a complete list of options in our documentation at https://lightning.ai"
            )

        if (
            accelerator not in self._accelerator_types
            and accelerator not in ("auto", "gpu")
            and not isinstance(accelerator, Accelerator)
        ):
            raise ValueError(
                f"You selected an invalid accelerator name: `accelerator={accelerator!r}`."
                f" Available names are: auto, {', '.join(self._accelerator_types)}."
            )

        # MPS accelerator is incompatible with DDP family of strategies. It supports single-device operation only.
        is_ddp_str = isinstance(strategy, str) and "ddp" in strategy
        is_deepspeed_str = isinstance(strategy, str) and "deepspeed" in strategy
        is_parallel_strategy = isinstance(strategy, ParallelStrategy) or is_ddp_str or is_deepspeed_str
        is_mps_accelerator = MPSAccelerator.is_available() and (
            accelerator in ("mps", "auto", "gpu", None) or isinstance(accelerator, MPSAccelerator)
        )
        if is_mps_accelerator and is_parallel_strategy:
            raise ValueError(
                f"You set `strategy={strategy}` but strategies from the DDP family are not supported on the"
                f" MPS accelerator. Either explicitly set `accelerator='cpu'` or change the strategy."
            )

        self._accelerator_flag = accelerator

View on GitHub (pinned to 9fed5c27d2)

Solutions

1. Use 'auto', 'gpu', 'cpu', 'mps', 'tpu', 'hpu', etc. — specifically replace 'cuda' with 'gpu'.
2. Or pass an Accelerator instance such as `lightning.pytorch.accelerators.CUDAAccelerator()`.
3. Alternatively set `devices` and leave accelerator='auto' to let Lightning pick.

Example fix

# before
trainer = Trainer(accelerator='cuda', devices=1)
# after
trainer = Trainer(accelerator='gpu', devices=1)

VALID = {'auto', 'gpu', 'cpu', 'mps', 'tpu', 'hpu', 'cuda'}  # normalize 'cuda'->'gpu'
accel = 'gpu' if accelerator == 'cuda' else accelerator
assert accel in {'auto','gpu','cpu','mps','tpu','hpu'} or hasattr(accel, 'setup'), f'bad accelerator {accelerator!r}'

from lightning.pytorch.accelerators import Accelerator

def is_valid_accelerator(a) -> bool:
    return isinstance(a, Accelerator) or (isinstance(a, str) and a.lower() in {'auto','gpu','cpu','mps','tpu','hpu'})

except ValueError as e: if 'invalid accelerator name' in str(e): normalize ('cuda'->'gpu') and retry Trainer construction

When it happens

Trigger: `Trainer(accelerator='cuda')` (invalid — should be 'gpu'), `accelerator='tpu'` without XLA support, `accelerator=3` or other non-string non-Accelerator values.

Common situations: Coming from raw PyTorch/HuggingFace where 'cuda' is the device string; passing torch.device objects or integers; typos like 'gpu '/ 'cpu-'.

Understand the failure class

Background: "Invalid configuration value" and "Unsupported/Unknown setting value" errors: why libraries reject your config strings, numbers, and types — this error's family across 30 libraries.

Related errors

• You requested to find {num_devices} devices but this machine
• You selected an invalid strategy name: `strategy={strategy!r
• f"`gradient_clip_algorithm` {gradient_clip_algorithm} is inv
• Device should be CUDA, got {device} instead.
• You requested to find {num_devices} devices but there are no

AI-assisted analysis of Lightning-AI/pytorch-lightning@9fed5c27d2 (2026-08-28). Data as JSON: /api/errors/2dcb9ad2fe209d53. Report an issue: GitHub.