[Kernel] Enable fast random sample on Kunlun P

vllm_kunlun/v1/sample/ops/topk_topp_sampler.py

@@ -151,7 +151,12 @@ def random_sample(
     # not have its own seed. Then, we overwrite the values for the requests
     # that have their own seeds.
     if len(generators) != probs.shape[0]:
-        q.exponential_()
+        if os.getenv('FAST_RANDOM_SAMPLE') == "1":
+            q.uniform_()
+            q = -torch.log(q)
+            q = q.clamp(min=1e-4)
+        else:
+            q.exponential_()
     if generators:
         # TODO(woosuk): This can be slow because we handle each request
         # one by one. Optimize this.