Add clear_streams API for cleanup before exit (#3395)

tests/scheduler_tests.cpp

@@ -48,8 +48,11 @@ TEST_CASE("test default stream in threads") {
   for (size_t i = 0; i < num_threads; ++i) {
     threads.emplace_back([&thread_streams, &mtx]() {
       auto s = default_stream(gpu::is_available() ? Device::gpu : Device::cpu);
-      std::lock_guard lock(mtx);
-      thread_streams.insert(s);
+      {
+        std::lock_guard lock(mtx);
+        thread_streams.insert(s);
+      }
+      clear_streams();
     });
   }
 
@@ -80,12 +83,27 @@ TEST_CASE("test access stream in other thread") {
     } catch (const std::runtime_error&) {
       error_caught = true;
     }
+    clear_streams();
   });
   t.join();
 
   CHECK(error_caught);
 }
 
+TEST_CASE("test new stream in threads") {
+  std::vector<std::thread> threads;
+  for (int i = 0; i < 1; ++i) {
+    threads.emplace_back([]() {
+      auto s = new_stream(default_device());
+      eval(arange(10, s));
+      clear_streams();
+    });
+  }
+  for (auto& t : threads) {
+    t.join();
+  }
+}
+
 TEST_CASE("test get streams") {
   // Initialize default CPU stream before querying
   default_stream(Device::cpu);