记忆与检索学习：从固定规则到可训练选择

import java.util.*;
public class Main {
    static void near(double expected,double actual) {
        if (!Double.isFinite(actual) || Math.abs(expected-actual)>1e-9*Math.max(1,Math.abs(expected)))
            throw new AssertionError(expected+" != "+actual);
    }
    static void check(boolean ok) { if(!ok) throw new AssertionError(); }
    static void bad(Runnable r) {
        try { r.run(); } catch(IllegalArgumentException e) { return; }
        throw new AssertionError("invalid input accepted");
    }
static int[] select(double[] relevance,double[][] similarity,int k,double lambda) {
        if(relevance==null||similarity==null||similarity.length!=relevance.length||k<0||k>relevance.length||!Double.isFinite(lambda)||lambda<0||lambda>1)
            throw new IllegalArgumentException("configuration");
        int n=relevance.length;
        for(int i=0;i<n;i++) {
            if(!Double.isFinite(relevance[i])||Math.abs(relevance[i])>1||similarity[i]==null||similarity[i].length!=n) throw new IllegalArgumentException("row");
            for(double x:similarity[i]) if(!Double.isFinite(x)||Math.abs(x)>1) throw new IllegalArgumentException("score");
        }
        boolean[] used=new boolean[n]; double[] maximum=new double[n]; int[] result=new int[k];
        Arrays.fill(maximum,Double.NEGATIVE_INFINITY); // 非空已选集合的最大相似度可为负，不能擅自截断为零。
        for(int t=0;t<k;t++) {
            int best=-1;double score=Double.NEGATIVE_INFINITY;
            for(int i=0;i<n;i++) if(!used[i]) {
                double value=t==0?relevance[i]:lambda*relevance[i]-(1-lambda)*maximum[i]; // 首项按相关性选取，明确空集合约定。
                if(value>score) {score=value;best=i;} // 顺序扫描使同分时选择较小编号。
            }
            used[best]=true;result[t]=best;
            for(int i=0;i<n;i++) maximum[i]=Math.max(maximum[i],similarity[i][best]); // 只追加新列，避免每轮重扫已选项。
        }
        return result;
    }
    public static void main(String[] args) {
double[] r={.9,.85,.6};double[][] s={{1,.99,.1},{.99,1,.2},{.1,.2,1}};
        check(Arrays.equals(select(r,s,2,.5),new int[]{0,2}));
        check(Arrays.equals(select(r,s,2,1),new int[]{0,1}));
        check(Arrays.equals(select(r,s,3,0),new int[]{0,2,1}));
        check(select(new double[]{},new double[][]{},0,.5).length==0);
        check(Arrays.equals(select(new double[]{.5,.5},new double[][]{{1,0},{0,1}},1,.5),new int[]{0}));
        check(Arrays.equals(select(new double[]{.9,.1,.1},new double[][]{{1,-.2,-.8},{-.2,1,0},{-.8,0,1}},2,0),new int[]{0,2}));
        bad(()->select(r,s,4,.5));
        bad(()->select(new double[]{Double.NaN},new double[][]{{1}},1,.5));
        System.out.println("PASS 8 cases");
    }
}