/*

  * 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.

  */

 package org.apache.giraph.block_app.reducers.collect;

 import org.apache.giraph.block_app.framework.api.BlockMasterApi;

 import org.apache.giraph.block_app.framework.api.CreateReducersApi;

 import org.apache.giraph.block_app.framework.piece.global_comm.BroadcastHandle;

 import org.apache.giraph.block_app.framework.piece.global_comm.ReducerHandle;

 import org.apache.giraph.block_app.framework.piece.global_comm.array.BroadcastArrayHandle;

 import org.apache.giraph.block_app.reducers.array.ArrayOfHandles;

 import org.apache.giraph.function.Supplier;

 import org.apache.giraph.master.MasterGlobalCommUsage;

 import org.apache.giraph.reducers.ReduceOperation;

 import org.apache.giraph.worker.WorkerBroadcastUsage;

 import org.apache.giraph.writable.kryo.KryoWritableWrapper;

 import org.apache.giraph.writable.kryo.TransientRandom;

 /**

  * Reducing values into a list of reducers, randomly,

  * and getting the results of all reducers together

  *

  * @param <S> Single value type

  * @param <R> Reduced value type

  */

 public abstract class ShardedReducerHandle<S, R>

     implements ReducerHandle<S, R> {

   // Use a prime number for number of reducers, large enough to make sure

   // request sizes are within expected size (0.5MB)

   protected static final int REDUCER_COUNT = 39989;

   protected final TransientRandom random = new TransientRandom();

   protected ArrayOfHandles.ArrayOfReducers<S, KryoWritableWrapper<R>> reducers;

   public final void register(final CreateReducersApi reduceApi) {

     reducers = new ArrayOfHandles.ArrayOfReducers<>(REDUCER_COUNT,

         new Supplier<ReducerHandle<S, KryoWritableWrapper<R>>>() {

           @Override

           public ReducerHandle<S, KryoWritableWrapper<R>> get() {

             return reduceApi.createLocalReducer(createReduceOperation());

           }

         });

   }

   @Override

   public final void reduce(S value) {

     reducers.get(random.nextInt(REDUCER_COUNT)).reduce(value);

   }

   @Override

   public final R getReducedValue(MasterGlobalCommUsage master) {

     KryoWritableWrapper<R> ret = new KryoWritableWrapper<>(

         createReduceResult(master));

     ReduceOperation<S, KryoWritableWrapper<R>> reduceOperation =

         createReduceOperation();

     for (int i = 0; i < REDUCER_COUNT; i++) {

       reduceOperation.reduceMerge(ret,

           reducers.get(i).getReducedValue(master));

     }

     return ret.get();

   }

   public abstract ReduceOperation<S, KryoWritableWrapper<R>>

   createReduceOperation();

   public R createReduceResult(MasterGlobalCommUsage master) {

     return createReduceOperation().createInitialValue().get();

   }

   public BroadcastHandle<R> createBroadcastHandle(

       BroadcastArrayHandle<KryoWritableWrapper<R>> broadcasts) {

     return new ShardedBroadcastHandle(broadcasts);

   }

   @Override

   public final BroadcastHandle<R> broadcastValue(BlockMasterApi masterApi) {

     return createBroadcastHandle(reducers.broadcastValue(masterApi));

   }

   /**

    * Broadcast for ShardedReducerHandle

    */

   public class ShardedBroadcastHandle implements BroadcastHandle<R> {

     protected final BroadcastArrayHandle<KryoWritableWrapper<R>> broadcasts;

     public ShardedBroadcastHandle(

         BroadcastArrayHandle<KryoWritableWrapper<R>> broadcasts) {

       this.broadcasts = broadcasts;

     }

     public R createBroadcastResult(WorkerBroadcastUsage worker) {

       return createReduceOperation().createInitialValue().get();

     }

     @Override

     public final R getBroadcast(WorkerBroadcastUsage worker) {

       KryoWritableWrapper<R> ret = new KryoWritableWrapper<>(

           createBroadcastResult(worker));

       ReduceOperation<S, KryoWritableWrapper<R>> reduceOperation =

           createReduceOperation();

       for (int i = 0; i < REDUCER_COUNT; i++) {

         reduceOperation.reduceMerge(ret,

             broadcasts.get(i).getBroadcast(worker));

       }

       return ret.get();

     }

   }

 }