add warning

python/tvm/contrib/thrust.py

@@ -16,9 +16,18 @@
 # under the License.
 """Utilities for thrust"""
 from tvm._ffi import get_global_func
+import logging
+
+
+def maybe_warn(target, func_name):
+    if get_global_func(func_name, allow_missing=True) and not "thrust" in target.libs:
+        logging.warning("TVM is built with thrust but thrust is not used.")
+    if "thrust" in target.libs and get_global_func(func_name, allow_missing=True) is None:
+        logging.warning("thrust is requested but TVM is not built with thrust.")
 
 
 def can_use_thrust(target, func_name):
+    maybe_warn(target, func_name)
     return (
         target.kind.name in ["cuda", "nvptx"]
         and "thrust" in target.libs
@@ -27,6 +36,7 @@ def can_use_thrust(target, func_name):
 
 
 def can_use_rocthrust(target, func_name):
+    maybe_warn(target, func_name)
     return (
         target.kind.name == "rocm"
         and "thrust" in target.libs