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Learing to Rank Query w/ RankLib Models

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/*
 * Copyright [2017] Doug Turnbull, Wikimedia Foundation
 *
 * Licensed 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.o19s.es.ltr.ranker.ranklib;

import ciir.umass.edu.learning.Ranker;
import ciir.umass.edu.learning.RankerFactory;
import com.o19s.es.ltr.feature.FeatureSet;
import com.o19s.es.ltr.ranker.LtrRanker;
import com.o19s.es.ltr.ranker.parser.LtrRankerParser;

/**
 * Load a ranklib model from a script file, mostly a wrapper around the
 * existing script that complies with the {@link LtrRankerParser} interface
 */
public class RanklibModelParser implements LtrRankerParser {
    public static final String TYPE = "model/ranklib";
    private final RankerFactory factory;

    public RanklibModelParser(RankerFactory factory) {
        this.factory = factory;
    }

    @Override
    public LtrRanker parse(FeatureSet set, String model) {
        Ranker ranklibRanker = factory.loadRankerFromString(model);
        int numFeatures = ranklibRanker.getFeatures().length;
        if (set != null) {
            numFeatures = set.size();
        }
        return new RanklibRanker(ranklibRanker, numFeatures);
    }
}