[MetaSchedule] Introduce MergedDatabase

Following up apache#12520 and apache#12626, this PR introduces `MergedDatabase`,
which allow users to compose multiple databases so that the high-level
IR could select the best tuning records among them.

The `MergedDatabase` also comes with an extra field `preferred` to allow
users to override tuning records from other databases. A classic usecase
of the `preferred` parameter is through handcrafted schedule functions:

```python
def schedule_fn(sch: tir.Schedule) -> bool:
  if "nn_conv2d" in sch.mod.attrs["task_name"]:
    handcrafted_scheduling(sch)
    return True
  return False

with ms.database.MergedDatabase(
  databases=[database],
  preferred=ms.database.ScheduleFn(schedule_fn),
):
  lib = relay.build(...)
```

include/tvm/meta_schedule/database.h

@@ -357,6 +357,14 @@ class Database : public runtime::ObjectRef {
    */
   TVM_DLL static Database JSONDatabase(String path_workload, String path_tuning_record,
                                        bool allow_missing);
+  /*!
+   * \brief Create a database merged from multiple databases.
+   * \param databases The databases to be merged.
+   * \param preferred The preferred database. If the preferred database responses to a query,
+   * all other databases will be ignored.
+   * \return The merged database.
+   */
+  TVM_DLL static Database MergedDatabase(Array<Database, void> merge, Optional<Database> preferred);
   /*!
    * \brief Create a database with customized methods on the python-side.
    * \param f_has_workload The packed function of `HasWorkload`.

python/tvm/meta_schedule/database/merged_database.py

@@ -0,0 +1,49 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+"""A database consists of multiple databases."""
+from typing import List, Optional
+
+from tvm._ffi import register_object
+
+from .. import _ffi_api
+from .database import Database
+
+
+@register_object("meta_schedule.MergedDatabase")
+class MergedDatabase(Database):
+    """A merged database from multiple databases"""
+
+    def __init__(
+        self,
+        databases: List[Database],
+        preferred: Optional[Database] = None,
+    ) -> None:
+        """Construct a merged database from multiple databases.
+
+        Parameters
+        ----------
+        databases : List[Database]
+            The list of databases to merge.
+        preferred : Optional[Database] = None
+            preferred The preferred database. If the preferred database responses to a query,
+            all other databases will be ignored.
+        """
+        self.__init_handle_by_constructor__(
+            _ffi_api.DatabaseMergedDatabase,  # type: ignore # pylint: disable=no-member
+            databases,
+            preferred,
+        )

src/meta_schedule/database/json_database.cc

@@ -25,28 +25,6 @@
 namespace tvm {
 namespace meta_schedule {
 
-/*! \brief The struct defining comparison function of sorting by mean run seconds. */
-struct SortTuningRecordByMeanRunSecs {
-  static const constexpr double kMaxMeanTime = 1e10;
-
-  static double Mean(const Array<FloatImm>& a) {
-    if (a.empty()) {
-      return kMaxMeanTime;
-    }
-    double sum = 0.0;
-    for (const FloatImm& i : a) {
-      sum += i->value;
-    }
-    return sum / a.size();
-  }
-
-  bool operator()(const TuningRecord& a, const TuningRecord& b) const {
-    double a_time = Mean(a->run_secs.value_or({}));
-    double b_time = Mean(b->run_secs.value_or({}));
-    return a_time < b_time;
-  }
-};
-
 /*!
  * \brief Read lines from a json file.
  * \param path The path to the json file.

src/meta_schedule/database/merged_database.cc

@@ -0,0 +1,101 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+#include "../utils.h"
+
+namespace tvm {
+namespace meta_schedule {
+
+class MergedDatabaseNode : public DatabaseNode {
+ public:
+  Array<Database> databases;
+  Optional<Database> preferred;
+
+  void VisitAttrs(AttrVisitor* v) {
+    v->Visit("databases", &databases);
+    v->Visit("preferred", &preferred);
+  }
+
+  static constexpr const char* _type_key = "meta_schedule.MergedDatabase";
+  TVM_DECLARE_FINAL_OBJECT_INFO(MergedDatabaseNode, DatabaseNode);
+
+ public:
+  Optional<TuningRecord> QueryTuningRecord(IRModule mod, Target target) final {
+    if (preferred) {
+      if (Optional<TuningRecord> record = preferred.value()->QueryTuningRecord(mod, target)) {
+        return record;
+      }
+    }
+    std::vector<TuningRecord> results;
+    results.reserve(databases.size());
+    for (const Database& db : databases) {
+      if (Optional<TuningRecord> record = db->QueryTuningRecord(mod, target)) {
+        results.push_back(record.value());
+      }
+    }
+    if (results.empty()) {
+      return NullOpt;
+    }
+    std::sort(results.begin(), results.end(), SortTuningRecordByMeanRunSecs());
+    return results[0];
+  }
+
+  bool HasWorkload(const IRModule& mod) final {
+    LOG(FATAL) << "NotImplementedError: MergedDatabase.HasWorkload";
+    throw;
+  }
+
+  Workload CommitWorkload(const IRModule& mod) final {
+    LOG(FATAL) << "NotImplementedError: MergedDatabase.CommitWorkload";
+    throw;
+  }
+
+  void CommitTuningRecord(const TuningRecord& record) final {
+    LOG(FATAL) << "NotImplementedError: MergedDatabase.CommitTuningRecord";
+    throw;
+  }
+
+  Array<TuningRecord> GetTopK(const Workload& workload, int top_k) final {
+    LOG(FATAL) << "NotImplementedError: MergedDatabase.GetTopK";
+    throw;
+  }
+
+  Array<TuningRecord> GetAllTuningRecords() final {
+    LOG(FATAL) << "NotImplementedError: MergedDatabase.GetAllTuningRecords";
+    throw;
+  }
+
+  int64_t Size() final {
+    LOG(FATAL) << "NotImplementedError: MergedDatabase.size";
+    throw;
+  }
+};
+
+Database Database::MergedDatabase(Array<Database> databases, Optional<Database> preferred) {
+  ObjectPtr<MergedDatabaseNode> n = make_object<MergedDatabaseNode>();
+  n->databases = std::move(databases);
+  n->preferred = std::move(preferred);
+  return Database(n);
+}
+
+TVM_REGISTER_NODE_TYPE(MergedDatabaseNode);
+TVM_REGISTER_GLOBAL("meta_schedule.DatabaseMergedDatabase")
+    .set_body_typed(Database::MergedDatabase);
+
+}  // namespace meta_schedule
+}  // namespace tvm

src/meta_schedule/utils.h

@@ -404,6 +404,28 @@ inline Array<Integer> AsIntArray(const ObjectRef& obj) {
   return results;
 }
 
+/*! \brief The struct defining comparison function of sorting by mean run seconds. */
+struct SortTuningRecordByMeanRunSecs {
+  static const constexpr double kMaxMeanTime = 1e10;
+
+  static double Mean(const Array<FloatImm>& a) {
+    if (a.empty()) {
+      return kMaxMeanTime;
+    }
+    double sum = 0.0;
+    for (const FloatImm& i : a) {
+      sum += i->value;
+    }
+    return sum / a.size();
+  }
+
+  bool operator()(const TuningRecord& a, const TuningRecord& b) const {
+    double a_time = Mean(a->run_secs.value_or({}));
+    double b_time = Mean(b->run_secs.value_or({}));
+    return a_time < b_time;
+  }
+};
+
 }  // namespace meta_schedule
 }  // namespace tvm