modelscope / modelscope/DiffSynth-Studio
When using gradient accumulation, does the order of optimizer.zero_grad() affect training?
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Description
if I use accelerate+deepspeed to train a model, and I set
deepspeed_config: gradient_accumulation_steps: 8 offload_optimizer_device: cpu offload_param_device: cpu zero3_init_flag: false zero_stage: 2
does the order of the order of backward(), step(), zero_grad() affect training?
For example:
for batch in training_dataloader: with accelerator.accumulate(model): inputs, targets = batch outputs = model(inputs) loss = loss_function(outputs, targets) accelerator.backward(loss) optimizer.step() scheduler.step() optimizer.zero_grad()
and
for batch in training_dataloader: with accelerator.accumulate(model): optimizer.zero_grad() inputs, targets = batch outputs = model(inputs) loss = loss_function(outputs, targets) accelerator.backward(loss) optimizer.step() scheduler.step()
I want to know whether the two situations will yield the same result. During gradient accumulation training, when the model needs to update the parameters and accelerate.sync_gradients=True, will using the second method clear the gradients, causing the gradient accumulation to be incorrect, so that at this point there is only one sample?
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Research direction
Start with the two training-loop variants in the issue, focusing on accelerator.accumulate(model), accelerator.backward(loss), optimizer.step(), scheduler.step(), and optimizer.zero_grad(). Compare their behavior when gradient accumulation is enabled and determine whether both loops preserve the intended accumulated gradients and produce equivalent updates.
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Assessment
- Tech stack
- python
- Domain
- machine-learning
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100