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Core Neural Networks Framework
There is a newer version: 2.1.0
/*
 * Copyright (c) 2019 by Andrew Charneski.
 *
 * The author 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 com.simiacryptus.mindseye.network;

import com.simiacryptus.lang.ref.ReferenceCountingBase;
import com.simiacryptus.mindseye.lang.Result;
import com.simiacryptus.mindseye.lang.Singleton;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.util.UUID;
import java.util.function.Supplier;

/**
 * A base class for a network node providing cached lazy evaluation; It gaurantees a node is only evaluated once, and
 * only if and when needed.
 */
@SuppressWarnings("serial")
abstract class LazyResult extends ReferenceCountingBase implements DAGNode {
  private static final Logger log = LoggerFactory.getLogger(LazyResult.class);
  /**
   * The Id.
   */
  public final UUID id;

  /**
   * Instantiates a new Lazy result.
   */
  public LazyResult() {
    this(UUID.randomUUID());
  }


  /**
   * Instantiates a new Lazy result.
   *
   * @param id the id
   */
  protected LazyResult(final UUID id) {
    super();
    this.id = id;
  }

  @Override
  public LazyResult addRef() {
    return (LazyResult) super.addRef();
  }

  /**
   * Eval nn result.
   *
   * @param t the t
   * @return the nn result
   */
  @Nullable
  protected abstract Result eval(GraphEvaluationContext t);

  @Nullable
  @Override
  public CountingResult get(@Nonnull final GraphEvaluationContext context) {
    context.assertAlive();
    assertAlive();
    long expectedCount = context.expectedCounts.getOrDefault(id, -1L);
    if (!context.calculated.containsKey(id)) {
      @Nullable Singleton singleton = null;
      synchronized (context) {
        if (!context.calculated.containsKey(id)) {
          singleton = new Singleton();
          context.calculated.put(id, singleton);
        }
      }
      if (null != singleton) {
        try {
          @Nullable Result result = eval(context);
          if (null == result) throw new IllegalStateException();
          singleton.set(new CountingResult(result));
          result.freeRef();
        } catch (Throwable e) {
          log.warn("Error execuing network component", e);
          singleton.set(e);
        }
      }
    }
    Supplier resultSupplier = context.calculated.get(id);
    if (null == resultSupplier) throw new IllegalStateException();
    Object obj = null == resultSupplier ? null : resultSupplier.get();
    if (obj != null && obj instanceof Throwable) throw new RuntimeException((Throwable) obj);
    if (obj != null && obj instanceof RuntimeException) throw ((RuntimeException) obj);
    @Nullable CountingResult nnResult = (CountingResult) obj;
    if (null == nnResult) throw new IllegalStateException();
    int references = nnResult.getAccumulator().increment();
    if (references <= 0) throw new IllegalStateException();
    if (expectedCount >= 0 && references > expectedCount) throw new IllegalStateException();
    if (expectedCount <= 0 || references < expectedCount) {
      nnResult.addRef();
      nnResult.getData().addRef();
    } else {
      context.calculated.remove(id);
    }
    return nnResult;
  }

  @Override
  public final UUID getId() {
    return id;
  }

}