Added implementation for calculating average

1 files changed, 193 insertions, 0 deletions

diff --git a/src/main/java/dev/morling/onebrc/CalculateAverage_Ujjwalbharti.java b/src/main/java/dev/morling/onebrc/CalculateAverage_Ujjwalbharti.java
new file mode 100644
index 0000000..8978475
--- /dev/null
+++ b/src/main/java/dev/morling/onebrc/CalculateAverage_Ujjwalbharti.java
@@ -0,0 +1,193 @@
+/*
+ *  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.IOException;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.nio.file.StandardOpenOption;
+import java.util.*;
+import java.util.concurrent.*;
+import java.util.stream.Collector;
+
+import static java.util.stream.Collectors.groupingBy;
+
+public class CalculateAverage_Ujjwalbharti {
+
+    private static final String FILE = "./measurements.txt";
+    private static final List<Map<String, MeasurementAggregator>> results = new CopyOnWriteArrayList<>();
+
+    private static record Measurement(String station, double value) {
+        private Measurement(String[] parts) {
+            this(parts[0], Double.parseDouble(parts[1]));
+        }
+    }
+
+    private static record ResultRow(double min, double mean, double max) {
+        public String toString() {
+            return round(min) + "/" + round(mean) + "/" + round(max);
+        }
+
+        private double round(double value) {
+            return Math.round(value * 10.0) / 10.0;
+        }
+    }
+
+    ;
+
+    private static class MeasurementAggregator {
+        private double min = Double.POSITIVE_INFINITY;
+        private double max = Double.NEGATIVE_INFINITY;
+        private double sum;
+        private long count;
+    }
+
+    private static class FileReaderCallable implements Callable<Void> {
+        private final Path filePath;
+        private final long startPos;
+        private final long endPos;
+
+        public FileReaderCallable(Path filePath, long startPos, long endPos) {
+            this.filePath = filePath;
+            this.startPos = startPos;
+            this.endPos = endPos;
+        }
+
+        @Override
+        public Void call() {
+
+            try (FileChannel channel = FileChannel.open(filePath, StandardOpenOption.READ)) {
+                channel.position(startPos);
+                ByteBuffer buffer = ByteBuffer.allocate((int) (endPos - startPos + 1));
+                channel.read(buffer);
+                String chunk = new String(buffer.array());
+                String[] chunkLines = chunk.split("\n");
+
+                Collector<Measurement, ?, MeasurementAggregator> collector = Collector.of(
+                        MeasurementAggregator::new,
+                        (a, m) -> {
+                            a.min = Math.min(a.min, m.value());
+                            a.max = Math.max(a.max, m.value());
+                            a.sum += m.value();
+                            a.count++;
+                        },
+                        (agg1, agg2) -> {
+                            var res = new MeasurementAggregator();
+                            res.min = Math.min(agg1.min, agg2.min);
+                            res.max = Math.max(agg1.max, agg2.max);
+                            res.sum = agg1.sum + agg2.sum;
+                            res.count = agg1.count + agg2.count;
+
+                            return res;
+                        });
+
+                Map<String, MeasurementAggregator> result = Arrays.stream(chunkLines)
+                        .map(line -> new Measurement(line.split(";")))
+                        .collect(groupingBy(Measurement::station, collector));
+
+                results.add(result);
+
+            }
+            catch (IOException e) {
+                e.printStackTrace();
+            }
+            return null;
+        }
+    }
+
+    private static long calculateEndPosition(Path path, long startPos, long chunkSize) throws IOException {
+        try (FileChannel channel = FileChannel.open(path, StandardOpenOption.READ)) {
+            if (startPos >= channel.size()) {
+                return -1;
+            }
+
+            long currentPos = startPos + chunkSize;
+            if (currentPos >= channel.size()) {
+                currentPos = channel.size() - 1;
+            }
+
+            channel.position(currentPos);
+            ByteBuffer buffer = ByteBuffer.allocate(1024);
+            int readBytes = channel.read(buffer);
+
+            if (readBytes > 0) {
+                for (int i = 0; i < readBytes; i++) {
+                    if (buffer.get(i) == '\n') {
+                        break;
+                    }
+                    currentPos++;
+                }
+            }
+
+            return currentPos;
+        }
+    }
+
+    public static void main(String[] args) throws IOException {
+        Path path = Paths.get(FILE);
+        long fileSize = Files.size(path);
+        long chunkSize = 1000 * 1000;
+        int nThread = (int) (fileSize / chunkSize);
+        var database = new HashMap<String, MeasurementAggregator>();
+        try (ExecutorService customExecutor = Executors.newFixedThreadPool(275)) {
+            var futures = new ArrayList<CompletableFuture<Void>>();
+            long startPos = 0;
+            for (int i = 0; i <= nThread; i++) {
+                long endPos = calculateEndPosition(path, startPos, chunkSize);
+                if (endPos == -1) {
+                    break;
+                }
+                long finalStartPos = startPos;
+                futures.add(CompletableFuture.runAsync(() -> new FileReaderCallable(path, finalStartPos, endPos).call(), customExecutor));
+                startPos = endPos + 1;
+            }
+            CompletableFuture<Void> allOfFuture = CompletableFuture.allOf(futures.toArray(new CompletableFuture[0]));
+            allOfFuture.get();
+        }
+        catch (Exception e) {
+            System.out.println(e.getMessage());
+        }
+
+        for (var map : results) {
+            for (String key : map.keySet()) {
+                if (database.containsKey(key)) {
+                    MeasurementAggregator mag1 = database.get(key);
+                    MeasurementAggregator mag2 = map.get(key);
+                    mag1.min = Math.min(mag1.min, mag2.min);
+                    mag1.max = Math.max(mag1.max, mag2.max);
+                    mag1.sum = mag1.sum + mag2.sum;
+                    mag1.count = mag1.count + mag2.count;
+                    database.put(key, mag1);
+                }
+                else {
+                    database.put(key, map.get(key));
+                }
+            }
+        }
+
+        var measurements = new TreeMap<String, ResultRow>();
+
+        for (String key : database.keySet()) {
+            MeasurementAggregator mag = database.get(key);
+            measurements.put(key, new ResultRow(mag.min, mag.sum / mag.count, mag.max));
+        }
+
+        System.out.println(measurements);
+    }
+}