float8nocompile: add e2e fsdp test

ghstack-source-id: 0525d57fe1e188dd6d8790c8d0b39e44d60b2f7b
ghstack-comment-id: 2576459235
Pull Request resolved: #1523

torchao/prototype/float8nocompile/test/fsdp_test.py

@@ -0,0 +1,97 @@
+######################################################################
+#
+# To run these unit tests, use the following command:
+#
+# torchrun --nproc_per_node=${NUM_GPUS} -m pytest test/fsdp_test.py
+#
+#######################################################################
+import os
+
+import pytest
+import torch
+import torch.distributed as dist
+import torch.nn as nn
+from torch.distributed.fsdp import FullyShardedDataParallel as FSDP
+
+from torchao.float8.float8_linear_utils import convert_to_float8_training
+from torchao.prototype.float8nocompile.float8nocompile_linear_utils import (
+    convert_to_float8_nocompile_training,
+)
+from torchao.utils import TORCH_VERSION_AT_LEAST_2_5
+
+if not TORCH_VERSION_AT_LEAST_2_5:
+    raise AssertionError("torchao.float8 requires PyTorch version 2.5 or greater")
+
+
+class TestModel(nn.Module):
+    def __init__(self):
+        super().__init__()
+        self.layers = nn.Sequential(
+            nn.Linear(2048, 4096, bias=False),
+            nn.Linear(4096, 16, bias=False),
+        )
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        return self.layers(x)
+
+
+def setup_distributed():
+    rank = int(os.environ["RANK"])
+    world_size = int(os.environ["WORLD_SIZE"])
+    dist.init_process_group("nccl", rank=rank, world_size=world_size)
+    torch.cuda.set_device(rank)
+
+
+@pytest.fixture
+def model1():
+    torch.manual_seed(0)
+    return TestModel()
+
+
+@pytest.fixture
+def model2():
+    torch.manual_seed(0)
+    return TestModel()
+
+
+def test_model_weights_and_gradients(model1, model2):
+    assert torch.cuda.is_available()
+    device = torch.device("cuda")
+
+    setup_distributed()
+
+    model1 = model1.to(torch.bfloat16).to(device)
+    model2 = model2.to(torch.bfloat16).to(device)
+
+    # compare production float8 linear conversion with no-compile version
+    convert_to_float8_training(model2)
+    convert_to_float8_nocompile_training(model1)
+
+    # distributed training with FSDP
+    model1 = FSDP(model1)
+    model2 = FSDP(model2)
+
+    input_tensor = torch.randn(
+        16, 2048, requires_grad=True, dtype=torch.bfloat16, device=device
+    )
+    input_copy1 = input_tensor.clone().detach().requires_grad_(True)
+    input_copy2 = input_tensor.clone().detach().requires_grad_(True)
+
+    loss_fn = nn.MSELoss()
+
+    output1 = model1(input_copy1)
+    output2 = model2(input_copy2)
+
+    loss1 = loss_fn(output1, torch.zeros_like(output1))
+    loss2 = loss_fn(output2, torch.zeros_like(output2))
+
+    loss1.backward()
+    loss2.backward()
+
+    dist.destroy_process_group()
+
+    # compare the outputs, weight gradients, and input gradients
+    assert torch.allclose(output1, output2, atol=0, rtol=0)
+    assert torch.allclose(input_copy1.grad, input_copy2.grad, atol=0, rtol=0)
+    for param1, param2 in zip(model1.parameters(), model2.parameters()):
+        assert torch.allclose(param1.grad, param2.grad, atol=0, rtol=0)