Use PackedSeqParams in accordance with changes in Megatron-LM (#8205)

* Use PackedSeqParams in accordance with changes in Megatron-LM

Signed-off-by: Chen Cui <chcui@nvidia.com>

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* add import guard for packed sequence

Signed-off-by: Chen Cui <chcui@nvidia.com>

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Signed-off-by: Chen Cui <chcui@nvidia.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Signed-off-by: stevehuang52 <heh@nvidia.com>

nemo/collections/nlp/models/language_modeling/megatron_gpt_model.py

@@ -19,11 +19,13 @@
 from contextlib import nullcontext
 from dataclasses import fields
 from functools import partial
+from importlib.metadata import version
 from typing import Any, Dict, Iterator, List, Optional, Union
 
 import torch
 from omegaconf import OmegaConf
 from omegaconf.dictconfig import DictConfig
+from pkg_resources import packaging
 from pytorch_lightning.accelerators import CPUAccelerator
 from pytorch_lightning.trainer.trainer import Trainer
 
@@ -925,12 +927,24 @@ def fwd_output_and_loss_func(dataloader_iter, model, checkpoint_activations_all_
                         cu_seqlens = cu_seqlens[: cu_seqlens_argmin.item()]
                     else:
                         cu_seqlens = cu_seqlens[: torch.argmin(cu_seqlens)]
-                    forward_args['cu_seqlens_q'] = cu_seqlens
-                    forward_args['cu_seqlens_kv'] = cu_seqlens
-                    if max_seqlen is not None:
-                        forward_args['max_seqlen_q'] = max_seqlen
-                        forward_args['max_seqlen_kv'] = max_seqlen
-                    forward_args['qkv_format'] = 'thd'
+
+                    try:
+                        from megatron.core.packed_seq_params import PackedSeqParams
+                    except (ImportError, ModuleNotFoundError) as e:
+                        mcore_version = packaging.version.Version(version('megatron-core'))
+                        logging.error(
+                            f"megatron-core v{mcore_version} does not support training with packed sequence. "
+                            "Please use megatron-core >= 0.5.0, or set model.data.train_ds.packed_sequence=False"
+                        )
+                        raise e
+
+                    forward_args['packed_seq_params'] = PackedSeqParams(
+                        cu_seqlens_q=cu_seqlens,
+                        cu_seqlens_kv=cu_seqlens,
+                        max_seqlen_q=max_seqlen,
+                        max_seqlen_kv=max_seqlen,
+                        qkv_format='thd',
+                    )
 
             output_tensor = model(**forward_args)