Adding Sam Pullara's submission;

calculate_average_spullara.sh

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+#!/bin/sh
+#
+#  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.
+#
+
+
+JAVA_OPTS=""
+time java $JAVA_OPTS --class-path target/average-1.0.0-SNAPSHOT.jar dev.morling.onebrc.CalculateAverage_spullara
+

src/main/java/dev/morling/onebrc/CalculateAverage_naive.java

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+/*
+ *  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.BufferedReader;
+import java.io.FileNotFoundException;
+import java.io.FileReader;
+import java.util.concurrent.ConcurrentSkipListMap;
+import java.util.stream.Collectors;
+
+public class CalculateAverage_naive {
+
+    record Result(double min, double max, double sum, long count) {
+    }
+
+    public static void main(String[] args) throws FileNotFoundException {
+        long start = System.currentTimeMillis();
+        var results = new BufferedReader(new FileReader("./measurements.txt"))
+                .lines()
+                .map(l -> l.split(";"))
+                .collect(Collectors.toMap(
+                        parts -> parts[0],
+                        parts -> {
+                            double temperature = Double.parseDouble(parts[1]);
+                            return new Result(temperature, temperature, temperature, 1);
+                        },
+                        (oldResult, newResult) -> {
+                            double min = Math.min(oldResult.min, newResult.min);
+                            double max = Math.max(oldResult.max, newResult.max);
+                            double sum = oldResult.sum + newResult.sum;
+                            long count = oldResult.count + newResult.count;
+                            return new Result(min, max, sum, count);
+                        }, ConcurrentSkipListMap::new));
+        System.out.println(System.currentTimeMillis() - start);
+        System.out.println(results);
+    }
+}

src/main/java/dev/morling/onebrc/CalculateAverage_spullara.java

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+/*
+ *  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.nio.channels.FileChannel;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardOpenOption;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.TreeMap;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Consumer;
+import java.util.function.Supplier;
+import java.util.stream.Collectors;
+
+public class CalculateAverage_spullara {
+  private static final String FILE = "./measurements.txt";
+
+    /*
+     * My results on this computer:
+     *
+     * CalculateAverage: 2m37.788s
+     * CalculateAverage_royvanrijn: 0m29.639s
+     * CalculateAverage_spullara: 0m2.013s
+     *
+     */
+
+  public static void main(String[] args) throws IOException, ExecutionException, InterruptedException {
+    var filename = args.length == 0 ? FILE : args[0];
+    var file = new File(filename);
+    long start = System.currentTimeMillis();
+
+    var totalLines = new AtomicInteger();
+    var results = getFileSegments(file).stream().map(segment -> {
+      var resultMap = new ByteArrayToResultMap();
+      long segmentEnd = segment.end();
+      try (var fileChannel = (FileChannel) Files.newByteChannel(Path.of(filename), StandardOpenOption.READ)) {
+        var bb = fileChannel.map(FileChannel.MapMode.READ_ONLY, segment.start(), segmentEnd - segment.start());
+        var buffer = new byte[64];
+        int lines = 0;
+        int startLine;
+        int limit = bb.limit();
+        while ((startLine = bb.position()) < limit) {
+          int currentPosition = startLine;
+          byte b;
+          int offset = 0;
+          while (currentPosition != segmentEnd && (b = bb.get(currentPosition++)) != ';') {
+            buffer[offset++] = b;
+          }
+          int temp = 0;
+          int negative = 1;
+          outer:
+          while (currentPosition != segmentEnd && (b = bb.get(currentPosition++)) != '\n') {
+            switch (b) {
+              case '-':
+                negative = -1;
+              case '.':
+                break;
+              case '\r':
+                currentPosition++;
+                break outer;
+              default:
+                temp = 10 * temp + (b - '0');
+            }
+          }
+          temp *= negative;
+          double finalTemp = temp / 10.0;
+          resultMap.putOrMerge(buffer, 0, offset,
+                  () -> new Result(finalTemp),
+                  measurement -> merge(measurement, finalTemp, finalTemp, finalTemp, 1));
+          lines++;
+          bb.position(currentPosition);
+        }
+        totalLines.addAndGet(lines);
+        return resultMap;
+      } catch (IOException e) {
+        throw new RuntimeException(e);
+      }
+    }).parallel().toList();
+
+    var resultMap = results.stream()
+            .flatMap(partition -> partition.getAll().stream())
+                    .collect(Collectors.toMap(e -> new String(e.key()), Entry::value, CalculateAverage_spullara::merge, TreeMap::new));
+
+    System.out.println("Time: " + (System.currentTimeMillis() - start) + "ms");
+    System.out.println("Lines processed: " + totalLines);
+    System.out.println(resultMap);
+  }
+
+  private static List<FileSegment> getFileSegments(File file) throws IOException {
+    int numberOfSegments = Runtime.getRuntime().availableProcessors();
+    long fileSize = file.length();
+    long segmentSize = fileSize / numberOfSegments;
+    List<FileSegment> segments = new ArrayList<>();
+    try (RandomAccessFile randomAccessFile = new RandomAccessFile(file, "r")) {
+      for (int i = 0; i < numberOfSegments; i++) {
+        long segStart = i * segmentSize;
+        long segEnd = (i == numberOfSegments - 1) ? fileSize : segStart + segmentSize;
+        segStart = findSegment(i, 0, randomAccessFile, segStart, segEnd);
+        segEnd = findSegment(i, numberOfSegments - 1, randomAccessFile, segEnd, fileSize);
+
+        segments.add(new FileSegment(segStart, segEnd));
+      }
+    }
+    return segments;
+  }
+
+  private static Result merge(Result v, Result value) {
+    return merge(v, value.min, value.max, value.sum, value.count);
+  }
+
+  private static Result merge(Result v, double value, double value1, double value2, long value3) {
+    v.min = Math.min(v.min, value);
+    v.max = Math.max(v.max, value1);
+    v.sum += value2;
+    v.count += value3;
+    return v;
+  }
+
+  private static long findSegment(int i, int skipSegment, RandomAccessFile raf, long location, long fileSize) throws IOException {
+    if (i != skipSegment) {
+      raf.seek(location);
+      while (location < fileSize) {
+        location++;
+        if (raf.read() == '\n')
+          break;
+      }
+    }
+    return location;
+  }
+}
+
+class Result {
+  double min, max, sum;
+  long count;
+
+  Result(double value) {
+    min = max = sum = value;
+    this.count = 1;
+  }
+
+  @Override
+  public String toString() {
+    return round(min) + "/" + round(sum / count) + "/" + round(max);
+  }
+
+  double round(double v) {
+    return Math.round(v * 10.0) / 10.0;
+  }
+
+}
+
+record Pair(int slot, Result slotValue) {
+}
+
+record Entry(byte[] key, Result value) {
+}
+
+record FileSegment(long start, long end) {
+}
+
+class ByteArrayToResultMap {
+  public static final int MAPSIZE = 1024*128;
+  Result[] slots = new Result[MAPSIZE];
+  byte[][] keys = new byte[MAPSIZE][];
+
+  private int hashCode(byte[] a, int fromIndex, int length) {
+    int result = 0;
+    int end = fromIndex + length;
+    for (int i = fromIndex; i < end; i++) {
+      result = 31 * result + a[i];
+    }
+    return result;
+  }
+
+  private Pair getPair(byte[] key, int offset, int size) {
+    int hash = hashCode(key, offset, size);
+    int slot = hash & (slots.length - 1);
+    var slotValue = slots[slot];
+    // Linear probe for open slot
+    while (slotValue != null && (keys[slot].length != size || !Arrays.equals(keys[slot], 0, size, key, offset, size))) {
+      slot = (slot + 1) & (slots.length - 1);
+      slotValue = slots[slot];
+    }
+    return new Pair(slot, slotValue);
+  }
+
+  public void putOrMerge(byte[] key, int offset, int size, Supplier<Result> supplier, Consumer<Result> merge) {
+    Pair result = getPair(key, offset, size);
+    Result value = result.slotValue();
+    if (value == null) {
+      int slot = result.slot();
+      slots[slot] = supplier.get();
+      byte[] bytes = new byte[size];
+      System.arraycopy(key, offset, bytes, 0, size);
+      keys[slot] = bytes;
+    } else {
+      merge.accept(value);
+    }
+  }
+
+  // Get all pairs
+  public List<Entry> getAll() {
+    List<Entry> result = new ArrayList<>();
+    for (int i = 0; i < slots.length; i++) {
+      Result slotValue = slots[i];
+      if (slotValue != null) {
+        result.add(new Entry(keys[i], slotValue));
+      }
+    }
+    return result;
+  }
+}