1 files changed, 113 insertions, 0 deletions
diff --git a/src/main/java/dev/morling/onebrc/CalculateAverage_criccomini.java b/src/main/java/dev/morling/onebrc/CalculateAverage_criccomini.java
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index 0000000..0e89bfc
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+++ b/src/main/java/dev/morling/onebrc/CalculateAverage_criccomini.java
@@ -0,0 +1,113 @@
+/*
+ *  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.MappedByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.charset.StandardCharsets;
+import java.util.*;
+import java.util.concurrent.*;
+
+public class CalculateAverage_criccomini {
+
+    private static final String FILE = "./measurements.txt";
+    private static final long FILE_SIZE = new File(FILE).length();
+    private static final long SEGMENT_SIZE = 256_000_000;
+
+    private static class MeasurementAggregator {
+        private double min = Double.POSITIVE_INFINITY;
+        private double max = Double.NEGATIVE_INFINITY;
+        private double sum;
+        private long count;
+
+        public String toString() {
+            return round(min) + "/" + round(sum / count) + "/" + round(max);
+        }
+
+        private double round(double value) {
+            return Math.round(value * 10.0) / 10.0;
+        }
+    }
+
+    private static Map<String, MeasurementAggregator> processSegment(MappedByteBuffer buffer, int length) {
+        Map<String, MeasurementAggregator> aggregates = new HashMap<>();
+        int lineStart = 0;
+        int doubleStart = 0;
+        String station = null;
+        for (int i = 0; i < length; ++i) {
+            byte b = buffer.get(i);
+            if (b == ';') {
+                byte[] stationBuffer = new byte[i - lineStart];
+                buffer.position(lineStart);
+                buffer.get(stationBuffer);
+                station = new String(stationBuffer, StandardCharsets.UTF_8);
+                doubleStart = i + 1;
+            }
+            else if (b == '\n') {
+                byte[] doubleBuffer = new byte[i - doubleStart];
+                buffer.position(doubleStart);
+                buffer.get(doubleBuffer);
+                Double temperature = Double.parseDouble(new String(doubleBuffer));
+                lineStart = i + 1;
+
+                MeasurementAggregator aggregator = aggregates.computeIfAbsent(station, s -> new MeasurementAggregator());
+                aggregator.min = Math.min(aggregator.min, temperature);
+                aggregator.max = Math.max(aggregator.max, temperature);
+                aggregator.sum += temperature;
+                aggregator.count++;
+            }
+        }
+        return aggregates;
+    }
+
+    public static void main(String[] args) throws IOException, InterruptedException, ExecutionException {
+        ExecutorService executor = Executors.newFixedThreadPool(128);
+        RandomAccessFile file = new RandomAccessFile(FILE, "r");
+        long position = 0;
+        List<Future<Map<String, MeasurementAggregator>>> futures = new ArrayList<>();
+        while (position < FILE_SIZE) {
+            int end = (int) Math.min(position + SEGMENT_SIZE, FILE_SIZE);
+            int length = (int) (end - position);
+            MappedByteBuffer buffer = file.getChannel().map(FileChannel.MapMode.READ_ONLY, position, length);
+            while (buffer.get(length - 1) != '\n') {
+                --length;
+            }
+            position += length;
+            int finalLength = length;
+            futures.add(executor.submit(() -> processSegment(buffer, finalLength)));
+        }
+
+        executor.shutdown();
+        executor.awaitTermination(Long.MAX_VALUE, TimeUnit.SECONDS);
+
+        // Merge results into a single TreeMap<String, MeasurementAggregator>
+        Map<String, MeasurementAggregator> aggregates = new TreeMap<>();
+        for (Future<Map<String, MeasurementAggregator>> future : futures) {
+            Map<String, MeasurementAggregator> segmentAggregates = future.get();
+            for (Map.Entry<String, MeasurementAggregator> entry : segmentAggregates.entrySet()) {
+                MeasurementAggregator aggregator = aggregates.computeIfAbsent(entry.getKey(), s -> new MeasurementAggregator());
+                aggregator.min = Math.min(aggregator.min, entry.getValue().min);
+                aggregator.max = Math.max(aggregator.max, entry.getValue().max);
+                aggregator.sum += entry.getValue().sum;
+                aggregator.count += entry.getValue().count;
+            }
+        }
+        System.out.println(aggregates);
+    }
+}