skip 3 steps in benchmarking

Author: Zhang Yan

dl_bench/utils.py

@@ -402,13 +402,14 @@ def inference(self, backend: Backend):
         self.net.eval()
         outputs = []
         fw_times = []
+        skip_steps = 3
         with torch.no_grad():
             start = time.perf_counter()
             # Duration is inconsistent now
             with tm.timeit("duration_s"):
-                while True:
+                for i, x in enumerate(test_loader):
                     s = get_time()
-                    x = backend.to_device(sample)
+                    x = backend.to_device(x)
                     if backend.dtype != torch.float32:
                         with torch.autocast(
                             device_type=backend.device_name,
@@ -417,7 +418,7 @@ def inference(self, backend: Backend):
                             y = self.net(x)
                     else:
                         y = self.net(x)
-
+                    if i < 3: continue
                     fw_times.append(get_time() - s)
                     n_items += len(x)
                     outputs.append(y)