com.yahoo.tensor.impl.Label Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of vespajlib Show documentation

Library for use in Java components of Vespa. Shared code which do not fit anywhere else.

There is a newer version: 8.409.18

// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.tensor.impl;

import com.yahoo.tensor.Tensor;

import java.util.Arrays;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * A label is a value of a mapped dimension of a tensor.
 * This class provides a mapping of labels to numbers which allow for more efficient computation with
 * mapped tensor dimensions.
 *
 * @author baldersheim
 */
public class Label {

    private static final String[] SMALL_INDEXES = createSmallIndexesAsStrings(1000);

    private final static Map string2Enum = new ConcurrentHashMap<>();

    // Index 0 is unused, that is a valid positive number
    // 1(-1) is reserved for the Tensor.INVALID_INDEX
    private static volatile String[] uniqueStrings = {"UNIQUE_UNUSED_MAGIC", "Tensor.INVALID_INDEX"};
    private static int numUniqeStrings = 2;

    private static String[] createSmallIndexesAsStrings(int count) {
        String[] asStrings = new String[count];
        for (int i = 0; i < count; i++) {
            asStrings[i] = String.valueOf(i);
        }
        return asStrings;
    }

    private static long addNewUniqueString(String s) {
        synchronized (string2Enum) {
            if (numUniqeStrings >= uniqueStrings.length) {
                uniqueStrings = Arrays.copyOf(uniqueStrings, uniqueStrings.length*2);
            }
            uniqueStrings[numUniqeStrings] = s;
            return -numUniqeStrings++;
        }
    }

    private static String asNumericString(long index) {
        return ((index >= 0) && (index < SMALL_INDEXES.length)) ? SMALL_INDEXES[(int)index] : String.valueOf(index);
    }

    private static boolean validNumericIndex(String s) {
        if (s.isEmpty() || ((s.length() > 1) && (s.charAt(0) == '0'))) return false;
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            if ((c < '0') || (c > '9')) return false;
        }
        return true;
    }

    public static long toNumber(String s) {
        if (s == null) { return Tensor.invalidIndex; }
        try {
            if (validNumericIndex(s)) {
                return Long.parseLong(s, 10);
            }
        } catch (NumberFormatException e) {
        }
        return string2Enum.computeIfAbsent(s, Label::addNewUniqueString);
    }

    public static String fromNumber(long v) {
        if (v >= 0) {
            return asNumericString(v);
        } else {
            if (v == Tensor.invalidIndex) { return null; }
            int index = -Convert.safe2Int(v);
            return uniqueStrings[index];
        }
    }

}