/*
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 *  * This program and the accompanying materials are made available under the
 *  * terms of the Apache License, Version 2.0 which is available at
 *  * https://www.apache.org/licenses/LICENSE-2.0.
 *  *
 *  *  See the NOTICE file distributed with this work for additional
 *  *  information regarding copyright ownership.
 *  * 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.
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package org.nd4j.linalg.api.ops.impl.transforms.custom.segment;

import org.nd4j.autodiff.samediff.SDVariable;
import org.nd4j.autodiff.samediff.SameDiff;
import org.nd4j.common.base.Preconditions;
import org.nd4j.linalg.api.buffer.DataType;
import org.nd4j.linalg.api.ndarray.INDArray;
import org.nd4j.linalg.api.ops.DynamicCustomOp;
import org.nd4j.linalg.api.ops.impl.transforms.segment.bp.SegmentSumBp;

import java.util.Collections;
import java.util.List;

public class SegmentSum extends DynamicCustomOp {

    public SegmentSum(SameDiff sameDiff, SDVariable data, SDVariable segmentIds) {
        super(null, sameDiff,  new SDVariable[] {data, segmentIds}, false);
    }

    public SegmentSum(){ }

    public SegmentSum(INDArray data, INDArray segmentIds){
        super(new INDArray[]{data, segmentIds}, null);
    }

    @Override
    public String opName(){
        return "segment_sum";
    }

    @Override
    public String tensorflowName() {
        return "SegmentSum";
    }

    @Override
    public List<SDVariable> doDiff(List<SDVariable> gradients){
        return new SegmentSumBp(sameDiff, arg(0), arg(1), gradients.get(0)).outputs();
    }

    @Override
    public List<DataType> calculateOutputDataTypes(List<DataType> inputDataTypes){
        Preconditions.checkState(inputDataTypes != null && inputDataTypes.size() == 2, "Expected exactly 2 input datatypes for %s, got %s", getClass(), inputDataTypes);
        Preconditions.checkState(inputDataTypes.get(1).isIntType(), "Datatype for input 1 (Segment IDs) must be an integer type, got %s", inputDataTypes.get(1));
        return Collections.singletonList(inputDataTypes.get(0));
    }

}
