SP cu_seqlens fix, refactor (#2495)

* working on masking fix

* refactor and fix multipack seqlens

* pre-commit fix

* adding smoke test

* using existing packed seqlens util

* log warning re: logged losses / gradient scaling per rank

tests/e2e/multigpu/test_sp.py

@@ -0,0 +1,87 @@
+"""E2E tests for sequence parallelism"""
+
+import os
+from pathlib import Path
+
+import yaml
+from accelerate.test_utils import execute_subprocess_async
+from transformers.testing_utils import get_torch_dist_unique_port
+
+from axolotl.utils.dict import DictDefault
+
+from ..utils import check_tensorboard
+
+os.environ["WANDB_DISABLED"] = "true"
+
+
+class TestSequenceParallelism:
+    """Test case for training with sequence parallelism enabled"""
+
+    def test_sequence_parallel_training(self, temp_dir):
+        # pylint: disable=duplicate-code
+        cfg = DictDefault(
+            {
+                "base_model": "HuggingFaceTB/SmolLM2-135M",
+                "load_in_8bit": False,
+                "load_in_4bit": True,
+                "strict": False,
+                "sequence_len": 2048,
+                "adapter": "qlora",
+                "sample_packing": True,
+                "eval_sample_packing": True,
+                "pad_to_sequence_len": True,
+                "lora_r": 8,
+                "lora_alpha": 16,
+                "lora_dropout": 0.05,
+                "lora_target_linear": True,
+                "lora_modules_to_save": ["embed_tokens", "lm_head"],
+                "special_tokens": {"pad_token": "<|endoftext|>"},
+                "datasets": [
+                    {
+                        "path": "tatsu-lab/alpaca",
+                        "type": "alpaca",
+                    },
+                ],
+                "num_epochs": 1,
+                "max_steps": 8,
+                "micro_batch_size": 1,
+                "gradient_accumulation_steps": 2,
+                "output_dir": temp_dir,
+                "learning_rate": 0.00001,
+                "optimizer": "adamw_8bit",
+                "lr_scheduler": "cosine",
+                "flash_attention": True,
+                "loss_watchdog_threshold": 5.0,
+                "loss_watchdog_patience": 3,
+                "bf16": "auto",
+                "warmup_steps": 1,
+                "saves_per_epoch": 1,
+                "logging_steps": 1,
+                "weight_decay": 0.0,
+                "use_tensorboard": True,
+                "sequence_parallel_degree": 2,
+            }
+        )
+
+        # write cfg to yaml file
+        Path(temp_dir).mkdir(parents=True, exist_ok=True)
+        with open(Path(temp_dir) / "config.yaml", "w", encoding="utf-8") as fout:
+            fout.write(yaml.dump(cfg.to_dict(), Dumper=yaml.Dumper))
+
+        execute_subprocess_async(
+            [
+                "accelerate",
+                "launch",
+                "--num-processes",
+                "2",
+                "--main_process_port",
+                f"{get_torch_dist_unique_port()}",
+                "-m",
+                "axolotl.cli.train",
+                str(Path(temp_dir) / "config.yaml"),
+            ]
+        )
+
+        check_tensorboard(
+            temp_dir + "/runs", "train/train_loss", 2.6, "Train Loss is too high"
+        )