[sc] add examples for auto checkpoint. (#1880)

examples/tutorial/auto_parallel/bench_utils.py

+import time
+from functools import partial
+from typing import Callable, Tuple
+
+import numpy as np
+import torch
+import torchvision.models as tm
+
+from colossalai.auto_parallel.checkpoint import CheckpointSolverRotor
+from colossalai.fx import metainfo_trace
+
+
+def bench(gm: torch.fx.GraphModule, criterion: torch.nn.Module, data_gen: Callable, num_steps: int = 5):
+    gm.train()
+    gm.cuda()
+    step_time = float('inf')
+    torch.cuda.synchronize()
+    torch.cuda.empty_cache()
+    torch.cuda.reset_peak_memory_stats()
+    cached = torch.cuda.max_memory_allocated(device="cuda")
+    try:
+        for _ in range(num_steps):
+            args, label = data_gen()
+            output, loss = None, None
+
+            torch.cuda.synchronize(device="cuda")
+            start = time.time()
+            output = gm(*args)
+            loss = criterion(output, label)
+            loss.backward()
+            torch.cuda.synchronize(device="cuda")
+            step_time = min(step_time, time.time() - start)
+
+            for child in gm.children():
+                for param in child.parameters():
+                    param.grad = None
+            del args, label, output, loss
+    except:
+        del args, label, output, loss
+    gm.to("cpu")
+    torch.cuda.empty_cache()
+    return (torch.cuda.max_memory_allocated(device="cuda") - cached) / 1024**2, step_time * 1.0e3
+
+
+def bench_rotor(gm: torch.fx.GraphModule,
+                criterion: torch.nn.Module,
+                data_gen: Callable,
+                num_steps: int = 5,
+                sample_points: int = 20,
+                free_memory: int = torch.cuda.mem_get_info()[0]):
+    peak_hist, step_hist = [], []
+    for budget in np.linspace(free_memory // 5, free_memory, sample_points):
+        gm = metainfo_trace(gm, *data_gen()[0])
+        solver = CheckpointSolverRotor(gm.graph, free_memory=budget)
+        try:
+            gm.graph = solver.solve()
+            peak_memory, step_time = bench(gm,
+                                           criterion,
+                                           partial(data_gen, batch_size=2048, shape=(3, 224, 224)),
+                                           num_steps=num_steps)
+        except:
+            peak_memory, step_time = budget / 1024**2, float('inf')
+        peak_hist.append(peak_memory)
+        step_hist.append(step_time)
+    return peak_hist, step_hist