From 53e64a938eab4886a49c6ae3caed055915c58352 Mon Sep 17 00:00:00 2001
From: Ke Wen <kw2501@meta.com>
Date: Thu, 13 Jun 2024 13:53:18 -0700
Subject: [PATCH] Cosmetic changes to train.py

ghstack-source-id: 75fe8612072535d205993416cfeca911099ea40d
Pull Request resolved: https://github.com/pytorch/torchtitan/pull/398
---
 train.py | 48 +++++++++++++++++++++++-------------------------
 1 file changed, 23 insertions(+), 25 deletions(-)

diff --git a/train.py b/train.py
index adbd975f..3d07199b 100644
--- a/train.py
+++ b/train.py
@@ -129,7 +129,7 @@ def main(job_config: JobConfig):
     gc.disable()
     gc.collect(1)
 
-    # init world mesh
+    # init distributed
     world_size = int(os.environ["WORLD_SIZE"])
     parallel_dims = ParallelDims(
         dp=job_config.training.data_parallel_degree,
@@ -142,15 +142,8 @@ def main(job_config: JobConfig):
     torch.cuda.set_device(device)
     init_distributed(job_config)
 
+    # build meshes
     world_mesh = parallel_dims.build_mesh(device_type="cuda")
-
-    model_name = job_config.model.name
-
-    # build tokenizer
-    tokenizer_type = model_name_to_tokenizer[model_name]
-    tokenizer = create_tokenizer(tokenizer_type, job_config.model.tokenizer_path)
-
-    # build dataloader
     if parallel_dims.dp_enabled:
         dp_mesh = world_mesh["dp"]
         dp_degree = dp_mesh.size()
@@ -161,6 +154,13 @@ def main(job_config: JobConfig):
     if parallel_dims.pp_enabled:
         pp_mesh = world_mesh["pp"]
 
+    model_name = job_config.model.name
+
+    # build tokenizer
+    tokenizer_type = model_name_to_tokenizer[model_name]
+    tokenizer = create_tokenizer(tokenizer_type, job_config.model.tokenizer_path)
+
+    # build dataloader
     data_loader = build_hf_data_loader(
         job_config.training.dataset,
         job_config.training.dataset_path,
@@ -191,10 +191,8 @@ def loss_fn(pred, labels):
     model_config.vocab_size = tokenizer.n_words
     model_config.max_seq_len = job_config.training.seq_len
 
+    logger.info(f"Building {model_name} {job_config.model.flavor} with {model_config}")
     with torch.device("meta"):
-        logger.info(
-            f"Building {model_name} {job_config.model.flavor} with {model_config}"
-        )
         model = model_cls.from_model_args(model_config)
 
     # apply fp8 linear module swap
@@ -236,7 +234,6 @@ def loss_fn(pred, labels):
     else:
         # If PP is enabled, we can't rely on init_weights, because some layers are missing.
         # In the future, we may make init_weights handle missing layers, but also have to consider RNG seed propagation.
-
         # allocate sharded model on GPU and initialize weights via DTensor
         model.init_weights()
 
@@ -249,7 +246,7 @@ def loss_fn(pred, labels):
 
     # build optimizer after applying parallelisms to the model
     optimizer = build_optimizer(model, job_config)
-    scheduler = get_lr_scheduler(optimizer, job_config)
+    lr_scheduler = get_lr_scheduler(optimizer, job_config)
 
     metric_logger = build_metric_logger(
         job_config, metrics_log_rank=get_metrics_rank(world_mesh, parallel_dims)
@@ -257,13 +254,13 @@ def loss_fn(pred, labels):
 
     train_state = TrainState()
 
-    # train loop
     model.train()
 
+    # load initial checkpoint
     checkpoint = CheckpointManager(
         model=model,
         optimizer=optimizer,
-        lr_scheduler=scheduler,
+        lr_scheduler=lr_scheduler,
         dataloader=data_loader,
         states={"train_state": train_state},
         job_config=job_config,
@@ -298,19 +295,20 @@ def loss_fn(pred, labels):
 
     data_iterator = iter(data_loader)
 
+    checkpoint.reset()
+
+    # variables used to keep info for metrics logging
+    losses_since_last_log: List[float] = []
+    ntokens_since_last_log = 0
+    data_loading_times: List[float] = []
+    time_last_log = timer()
+    gpu_memory_monitor.reset_peak_stats()
+
+    # train loop
     logger.info(f"Training starts at step {train_state.step + 1}")
     with maybe_enable_profiling(
         job_config, global_step=train_state.step
     ) as torch_profiler:
-        checkpoint.reset()
-
-        # variables used to keep info for metrics logging
-        losses_since_last_log: List[float] = []
-        ntokens_since_last_log = 0
-        data_loading_times: List[float] = []
-        time_last_log = timer()
-        gpu_memory_monitor.reset_peak_stats()
-
         while train_state.step < job_config.training.steps:
             train_state.step += 1
             if train_state.step > 1 and train_state.step % _gc_freq == 0: