validate use_remove_padding when applying sequence parallelism

[chujiezheng]

This is because the ulysses_sp is activated only when use_remove_padding is enabled:

verl/verl/workers/actor/dp_actor.py

Lines 71 to 128 in ab525bc

	if self.use_remove_padding:
	input_ids_rmpad, indices, *_ = unpad_input(input_ids.unsqueeze(-1),
	attention_mask) # input_ids_rmpad (total_nnz, ...)
	input_ids_rmpad = input_ids_rmpad.transpose(0, 1) # (1, total_nnz)
	# unpad the position_ids to align the rotary
	position_ids_rmpad = index_first_axis(rearrange(position_ids.unsqueeze(-1), "b s ... -> (b s) ..."),
	indices).transpose(0, 1)
	# for compute the log_prob
	input_ids_rmpad_rolled = torch.roll(input_ids_rmpad, shifts=-1, dims=1) # (1, total_nnz)
	# pad and slice the inputs if sp > 1
	if self.use_ulysses_sp:
	input_ids_rmpad, position_ids_rmpad, pad_size = ulysses_pad_and_slice_inputs(input_ids_rmpad, \
	position_ids_rmpad, \
	sp_size=self.ulysses_sequence_parallel_size)
	input_ids_rmpad_rolled, _, _ = ulysses_pad_and_slice_inputs(input_ids_rmpad_rolled, None,
	self.ulysses_sequence_parallel_size)
	input_ids_rmpad_rolled = input_ids_rmpad_rolled.squeeze(0) # ((total_nnz / sp) + pad)
	# only pass input_ids and position_ids to enable flash_attn_varlen
	output = self.actor_module(input_ids=input_ids_rmpad,
	attention_mask=None,
	position_ids=position_ids_rmpad,
	use_cache=False) # prevent model thinks we are generating
	logits_rmpad = output.logits.squeeze(0) # (total_nnz, vocab_size)
	logits_rmpad.div_(temperature)
	# compute entropy
	entropy_rmpad = self.compute_entropy_from_logits(logits_rmpad) # ((total_nnz / sp) + pad)
	# if use_sp: ((total_nnz / sp) + pad) ; if not use_sp: (batch, seqlen)
	log_probs = logprobs_from_logits(logits=logits_rmpad, labels=input_ids_rmpad_rolled)
	# gather log_prob if sp > 1
	if self.use_ulysses_sp:
	# gather and unpad for the ulysses sp
	log_probs = gather_outpus_and_unpad(log_probs, gather_dim=0, unpad_dim=0, padding_size=pad_size)
	entropy_rmpad = gather_outpus_and_unpad(entropy_rmpad,
	gather_dim=0,
	unpad_dim=0,
	padding_size=pad_size)
	# pad back to (bsz, seqlen)
	full_entropy = pad_input(hidden_states=entropy_rmpad.unsqueeze(-1),
	indices=indices,
	batch=batch_size,
	seqlen=seqlen)
	full_log_probs = pad_input(hidden_states=log_probs.unsqueeze(-1),
	indices=indices,
	batch=batch_size,
	seqlen=seqlen)
	# only return response part:
	entropy = full_entropy.squeeze(-1)[:, -response_length - 1:-1] # (bsz, response_length)
	log_probs = full_log_probs.squeeze(-1)[:, -response_length - 1:-1] # (bsz, response_length)

Without this check, users may encounter OOM issues when the set sp_size > 1 but use_remove_padding is mistakenly disabled.

[vermouth1992]

Could you format the code by running bash script/format.sh

[chujiezheng]

Done!

[vermouth1992]

It seems that the correct key is config. actor_rollout_ref.model.use_remove_padding, critic.model.use_remove_padding and reward_model.model.use_remove_padding

[chujiezheng]

Fixed now!