1brc/src/main/java/dev/morling/onebrc/CalculateAverage_jgrateron.java

/*
 *  Copyright 2023 The original authors
 *
 *  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 dev.morling.onebrc;

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Locale;
import java.util.Queue;
import java.util.Map.Entry;
import java.util.stream.Collectors;

public class CalculateAverage_jgrateron {
    private static final String FILE = "./measurements.txt";
    private static final int MAX_LENGTH_LINE = 115;
    private static final int MAX_BUFFER = 1024 * 8;
    private static boolean DEBUG = false;

    public record Particion(long offset, long size) {
    }

    public record Tupla(String str, double num) {
    }

    /*
     * 
     */
    public static List<Particion> dividirArchivo(File archivo) throws IOException {
        var particiones = new ArrayList<Particion>();
        var buffer = new byte[MAX_LENGTH_LINE];
        var length = archivo.length();
        int cores = Runtime.getRuntime().availableProcessors();
        var sizeParticion = length / cores;
        if (sizeParticion > MAX_BUFFER) {
            var ini = 0l;
            try (var rfile = new RandomAccessFile(archivo, "r")) {
                for (;;) {
                    var size = sizeParticion;
                    var pos = ini + size;
                    if (pos > length) {
                        pos = length - 1;
                        size = length - ini;
                    }
                    rfile.seek(pos);
                    int count = rfile.read(buffer);
                    if (count == -1) {
                        break;
                    }
                    for (int i = 0; i < count; i++) {
                        size++;
                        if (buffer[i] == '\n' || buffer[i] == '\r') {
                            break;
                        }
                    }
                    var particion = new Particion(ini, size);
                    particiones.add(particion);
                    if (count != buffer.length) {
                        break;
                    }
                    ini += size;
                }
            }
        }
        else {
            particiones.add(new Particion(0, length));
        }
        return particiones;
    }

    public static void main(String[] args) throws InterruptedException, IOException {
        Locale.setDefault(Locale.US);
        var startTime = System.nanoTime();
        var archivo = new File(FILE);
        var totalMediciones = new HashMap<Integer, Medicion>();
        var tareas = new ArrayList<Thread>();
        var particiones = dividirArchivo(archivo);

        for (var p : particiones) {
            var hilo = Thread.ofVirtual().start(() -> {
                var mediciones = new HashMap<Integer, Medicion>();
                try (var miArchivo = new MiArchivo(archivo)) {
                    miArchivo.seek(p);
                    for (;;) {
                        var tuples = miArchivo.readTuples();
                        if (tuples.isEmpty()) {
                            break;
                        }
                        for (;;) {
                            var tuple = tuples.poll();
                            if (tuple == null) {
                                break;
                            }
                            var estacion = tuple.str;
                            var temp = tuple.num;
                            var hashCode = estacion.hashCode();
                            var medicion = mediciones.get(hashCode);
                            if (medicion == null) {
                                medicion = new Medicion(estacion, 1, temp, temp, temp);
                                mediciones.put(hashCode, medicion);
                            }
                            else {
                                medicion.update(1, temp, temp, temp);
                            }
                        }
                    }
                }
                catch (IOException e) {
                    System.exit(-1);
                }
                synchronized (totalMediciones) {
                    for (var entry : mediciones.entrySet()) {
                        var medicion = totalMediciones.get(entry.getKey());
                        if (medicion == null) {
                            totalMediciones.put(entry.getKey(), entry.getValue());
                        }
                        else {
                            var otraMed = entry.getValue();
                            medicion.update(otraMed.count, otraMed.tempMin, otraMed.tempMax, otraMed.tempSum);
                        }
                    }
                }
            });
            tareas.add(hilo);
        }
        for (var hilo : tareas) {
            hilo.join();
        }

        Comparator<Entry<Integer, Medicion>> comparar = (a, b) -> {
            return a.getValue().estacion.compareTo(b.getValue().estacion);
        };

        var result = totalMediciones.entrySet().stream()//
                .sorted(comparar)//
                .map(e -> e.getValue().toString())//
                .collect(Collectors.joining(", "));

        System.out.println("{" + result + "}");
        if (DEBUG) {
            System.out.println("Total: " + (System.nanoTime() - startTime) / 1000000 + "ms");
        }

    }

    /*
     * 
     */
    public static double strToDouble(byte linea[], int posSeparator, int len) {
        double number[] = { 0, 0 };
        int pos = 0;
        boolean esNegativo = false;
        for (int i = posSeparator + 1; i < len; i++) {
            switch (linea[i]) {
                case '0', '1', '2', '3', '4':
                case '5', '6', '7', '8', '9':
                    number[pos] = number[pos] * 10;
                    number[pos] = number[pos] + (linea[i] - 48);
                    break;
                case '-':
                    esNegativo = true;
                    break;
                case '.':
                    pos = 1;
                    break;
            }
        }
        double num = number[0];
        if (number[1] > 0) {
            num += (number[1] / 10);
        }
        if (esNegativo) {
            num = num * -1;
        }
        return num;
    }

    /*
     * 
     */
    static class MiArchivo implements AutoCloseable {
        private final RandomAccessFile rFile;
        private final byte buffer[] = new byte[MAX_BUFFER];
        private final byte line[] = new byte[MAX_LENGTH_LINE];
        private final byte rest[] = new byte[MAX_LENGTH_LINE];
        private int lenRest = 0;
        private long maxRead = 0;
        private long totalRead = 0;
        private Queue<Tupla> tuples = new LinkedList<Tupla>();

        public MiArchivo(File file) throws IOException {
            rFile = new RandomAccessFile(file, "r");
        }

        public void seek(Particion particion) throws IOException {
            maxRead = particion.size;
            rFile.seek(particion.offset);
        }

        @Override
        public void close() throws IOException {
            rFile.close();
        }

        public Queue<Tupla> readTuples() throws IOException {
            if (totalRead == maxRead) {
                return tuples;
            }
            long numBytes = rFile.read(buffer);
            if (numBytes == -1) {
                return tuples;
            }
            var totalLeidos = totalRead + numBytes;
            if (totalLeidos > maxRead) {
                numBytes = maxRead - totalRead;
            }
            totalRead += numBytes;
            int pos = 0;
            int len = 0;
            int idx = 0;
            while (pos < numBytes) {
                if (buffer[pos] == '\n' || buffer[pos] == '\r') {
                    if (lenRest > 0) {
                        System.arraycopy(rest, 0, line, 0, lenRest);
                        System.arraycopy(buffer, idx, line, lenRest, len);
                        len += lenRest;
                        lenRest = 0;
                    }
                    else {
                        System.arraycopy(buffer, idx, line, 0, len);
                    }
                    int semicolon = 0;
                    for (int i = 0; i < len; i++) {
                        if (line[i] == ';') {
                            semicolon = i;
                            break;
                        }
                    }
                    var temperatura = strToDouble(line, semicolon, len);
                    var tupla = new Tupla(new String(line, 0, semicolon), temperatura);
                    tuples.add(tupla);
                    idx = pos + 1;
                    len = 0;
                }
                else {
                    len++;
                }
                pos++;
            }
            if (len > 0) {
                System.arraycopy(buffer, idx, rest, 0, len);
                lenRest = len;
            }
            return tuples;
        }
    }

    /*
     * 
     */
    static class Medicion {
        private String estacion;
        private int count;
        private double tempMin;
        private double tempMax;
        private double tempSum;

        public Medicion(String estacion, int count, double tempMin, double tempMax, double tempSum) {
            super();
            this.estacion = estacion;
            this.count = count;
            this.tempMin = tempMin;
            this.tempMax = tempMax;
            this.tempSum = tempSum;
        }

        public void update(int count, double tempMin, double tempMax, double tempSum) {
            this.count += count;
            if (tempMin < this.tempMin) {
                this.tempMin = tempMin;
            }
            if (tempMax > this.tempMax) {
                this.tempMax = tempMax;
            }
            this.tempSum += tempSum;
        }

        @Override
        public String toString() {
            double tempPro = tempSum / count;
            return "%s=%.1f/%.1f/%.1f".formatted(estacion, tempMin, tempPro, tempMax);
        }
    }
}