1 files changed, 256 insertions, 0 deletions
diff --git a/src/main/java/dev/morling/onebrc/CalculateAverage_JesseVanRooy.java b/src/main/java/dev/morling/onebrc/CalculateAverage_JesseVanRooy.java
new file mode 100644
index 0000000..ba0475e
--- /dev/null
+++ b/src/main/java/dev/morling/onebrc/CalculateAverage_JesseVanRooy.java
@@ -0,0 +1,256 @@
+/*
+ *  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 sun.misc.Unsafe;
+
+import java.io.IOException;
+import java.lang.foreign.Arena;
+import java.lang.foreign.MemorySegment;
+import java.lang.foreign.ValueLayout;
+import java.lang.reflect.Field;
+import java.nio.channels.FileChannel;
+import java.nio.file.Path;
+import java.nio.file.StandardOpenOption;
+import java.util.*;
+import java.util.stream.IntStream;
+
+//Disclaimer: The idea from the segmentation into #core amount of chunks came from previously submitted solutions.
+public class CalculateAverage_JesseVanRooy {
+
+    private static final String FILE = "./measurements.txt";
+
+    private static final ValueLayout.OfByte DATA_LAYOUT = ValueLayout.JAVA_BYTE;
+
+    private static final Unsafe UNSAFE = initUnsafe();
+
+    private static Unsafe initUnsafe() {
+        try {
+            Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
+            theUnsafe.setAccessible(true);
+            return (Unsafe) theUnsafe.get(Unsafe.class);
+        }
+        catch (NoSuchFieldException | IllegalAccessException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public static class Result {
+        long nameStart;
+        long nameSize;
+        String name;
+        int min;
+        int max;
+        long sum;
+        int count;
+
+        double min() {
+            return min / 10.0;
+        }
+
+        double max() {
+            return max / 10.0;
+        }
+
+        double mean() {
+            return (sum / 10.0) / count;
+        }
+    }
+
+    public static class ThreadResult {
+        Result[] results;
+    }
+
+    static final int MAP_SIZE = 16384;
+    static final int MAP_MASK = MAP_SIZE - 1;
+    static final int VALUE_CAPACITY = 10000;
+
+    static void process(MemorySegment memorySegment, ThreadResult threadResult) {
+        // initialize hash table
+        final int[] keys = new int[MAP_SIZE];
+        Arrays.fill(keys, -1);
+        final Result[] values = new Result[MAP_SIZE];
+
+        // pre-create the result objects
+        final Result[] preCreatedResults = new Result[VALUE_CAPACITY];
+        int usedPreCreatedResults = 0;
+        for (int i = 0; i < VALUE_CAPACITY; i++)
+            preCreatedResults[i] = new Result();
+
+        // load address info
+        final long size = memorySegment.byteSize();
+        final long address = memorySegment.address();
+        final long end = address + size;
+
+        for (long index = address; index < end;) {
+            final long nameStart = index;
+
+            byte next = UNSAFE.getByte(index);
+
+            // hash the city name
+            int hash = 0;
+            while (next != ';') {
+                hash = (hash * 33) + next;
+
+                index++;
+                next = UNSAFE.getByte(index);
+            }
+
+            final long nameEnd = index;
+
+            // skip the separator
+            index++;
+            next = UNSAFE.getByte(index);
+
+            // check for negative
+            boolean negative = next == '-';
+            if (negative) {
+                index++;
+                next = UNSAFE.getByte(index);
+            }
+
+            // count the temperature
+            int temperature = next - '0';
+            index++;
+            next = UNSAFE.getByte(index);
+
+            if (next != '.') {
+                temperature = (temperature * 10) + (next - '0');
+                index++;
+            }
+
+            // skip the .
+            index++;
+            next = UNSAFE.getByte(index);
+
+            // add the last digit to temperature
+            temperature = (temperature * 10) + (next - '0');
+            index++;
+
+            // negate the temperature if needed
+            if (negative) {
+                temperature = -temperature;
+            }
+
+            // skip the newline
+            index++;
+
+            // insert into map
+            for (int i = hash; i < hash + MAP_SIZE; i++) {
+                int mapIndex = i & MAP_MASK;
+                if (keys[mapIndex] == -1) {
+                    Result result = preCreatedResults[usedPreCreatedResults++];
+                    result.nameStart = nameStart;
+                    result.nameSize = nameEnd - nameStart;
+                    result.min = temperature;
+                    result.max = temperature;
+                    result.sum = temperature;
+                    result.count = 1;
+
+                    keys[mapIndex] = hash;
+                    values[mapIndex] = result;
+                    break;
+                }
+                if (keys[mapIndex] == hash) {
+                    Result result = values[mapIndex];
+                    result.min = Math.min(result.min, temperature);
+                    result.max = Math.max(result.max, temperature);
+                    result.sum += temperature;
+                    result.count++;
+                    break;
+                }
+            }
+        }
+
+        threadResult.results = Arrays.stream(values).filter(Objects::nonNull).toArray(Result[]::new);
+
+        for (Result result : threadResult.results) {
+            result.name = new String(memorySegment.asSlice(result.nameStart - address, result.nameSize).toArray(DATA_LAYOUT));
+        }
+    }
+
+    public static void main(String[] args) throws IOException, InterruptedException {
+        int numberOfChunks = Runtime.getRuntime().availableProcessors();
+
+        try (var fileChannel = FileChannel.open(Path.of(FILE), StandardOpenOption.READ)) {
+
+            long fileSize = fileChannel.size();
+            MemorySegment allData = fileChannel.map(FileChannel.MapMode.READ_ONLY, 0, fileSize, Arena.global());
+
+            long segmentSize = (fileSize + numberOfChunks - 1) / numberOfChunks;
+            long[] segmentBounds = new long[numberOfChunks + 1];
+
+            segmentBounds[0] = 0;
+            for (int i = 1; i < numberOfChunks; i++) {
+                long chunkAddress = i * segmentSize;
+                while (chunkAddress < fileSize && allData.getAtIndex(DATA_LAYOUT, chunkAddress++) != '\n') {
+                }
+                segmentBounds[i] = Math.min(chunkAddress, fileSize);
+            }
+            segmentBounds[numberOfChunks] = fileSize;
+
+            ThreadResult[] threadResults = IntStream.range(0, numberOfChunks)
+                    .parallel()
+                    .mapToObj(i -> {
+                        long size = segmentBounds[i + 1] - segmentBounds[i];
+                        long offset = segmentBounds[i];
+                        MemorySegment segment = allData.asSlice(offset, size);
+                        ThreadResult result = new ThreadResult();
+                        process(segment, result);
+                        return result;
+                    })
+                    .toArray(ThreadResult[]::new);
+
+            HashMap<String, Result> combinedResults = new HashMap<>(1024);
+
+            for (int i = 0; i < numberOfChunks; i++) {
+                for (Result result : threadResults[i].results) {
+                    if (!combinedResults.containsKey(result.name)) {
+                        Result newResult = new Result();
+                        newResult.name = result.name;
+                        newResult.min = result.min;
+                        newResult.max = result.max;
+                        newResult.sum = result.sum;
+                        newResult.count = result.count;
+                        combinedResults.put(result.name, newResult);
+                    }
+                    else {
+                        Result existingResult = combinedResults.get(result.name);
+                        existingResult.min = Math.min(existingResult.min, result.min);
+                        existingResult.max = Math.max(existingResult.max, result.max);
+                        existingResult.sum += result.sum;
+                        existingResult.count += result.count;
+                    }
+                }
+            }
+
+            Result[] sortedResults = combinedResults.values().toArray(Result[]::new);
+            Arrays.sort(sortedResults, Comparator.comparing(result -> result.name));
+
+            System.out.print("{");
+
+            for (int i = 0; i < sortedResults.length; i++) {
+                Result sortedResult = sortedResults[i];
+                if (i != 0) {
+                    System.out.print(", ");
+                }
+                System.out.printf(Locale.US, "%s=%.1f/%.1f/%.1f", sortedResult.name, sortedResult.min(), sortedResult.mean(), sortedResult.max());
+            }
+
+            System.out.printf("}\n");
+        }
+    }
+}