First attempt with Java-managed concurrency (#590)

Co-authored-by: Quang Hieu Dao <hieu_dq@flinters.vn>

calculate_average_dqhieuu.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=""
+java $JAVA_OPTS --class-path target/average-1.0.0-SNAPSHOT.jar dev.morling.onebrc.CalculateAverage_dqhieuu

prepare_dqhieuu.sh

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+#!/bin/bash
+#
+#  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.
+#
+
+# Uncomment below to use sdk
+# source "$HOME/.sdkman/bin/sdkman-init.sh"
+# sdk use java 21.0.1-graal 1>&2

src/main/java/dev/morling/onebrc/CalculateAverage_dqhieuu.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.IOException;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.util.Map;
+import java.util.TreeMap;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
+
+public class CalculateAverage_dqhieuu {
+    private static final String FILE = "measurements.txt";
+
+    private static double round(double value) {
+        return Math.round(value * 10.0) / 10.0;
+    }
+
+    private static class MeasurementAggregator {
+        private Lock lock = new ReentrantLock();
+        private double min = Double.POSITIVE_INFINITY;
+        private double max = Double.NEGATIVE_INFINITY;
+        private double sum = 0;
+        private int count = 0;
+
+        @Override
+        public String toString() {
+            return round(min) + "/" + round(round(sum) / count) + "/" + round(max);
+        }
+    }
+
+    public static void main(String[] args) throws IOException {
+        var lineStream = Files.lines(Paths.get(FILE)).parallel();
+
+        Map<String, MeasurementAggregator> measurements = new ConcurrentHashMap<>(10_000);
+
+        lineStream.forEach(
+                l -> {
+                    var sepIdx = 0;
+                    while (l.charAt(sepIdx) != ';') {
+                        sepIdx++;
+                    }
+
+                    var station = l.substring(0, sepIdx);
+
+                    int valueInt = 0;
+                    int sign = l.charAt(sepIdx + 1) == '-' ? -1 : 1;
+
+                    var lineLength = l.length();
+                    for (var i = sepIdx + 1; i < lineLength; i++) {
+                        var c = l.charAt(i);
+                        if (c == '-' || c == '.') {
+                            continue;
+                        }
+                        valueInt = valueInt * 10 + (c - '0');
+                    }
+
+                    var value = ((double) valueInt / 10.0) * sign;
+
+                    var agg = measurements.computeIfAbsent(station, k -> new MeasurementAggregator());
+
+                    agg.lock.lock();
+
+                    if (value < agg.min) {
+                        agg.min = value;
+                    }
+                    if (value > agg.max) {
+                        agg.max = value;
+                    }
+                    agg.sum += value;
+                    agg.count++;
+
+                    agg.lock.unlock();
+                });
+
+        Map<String, MeasurementAggregator> sortedEntries = new TreeMap<>(measurements);
+
+        var res = new StringBuilder();
+        res.append("{");
+
+        var first = true;
+        for (var entry : sortedEntries.entrySet()) {
+            if (first) {
+                first = false;
+            }
+            else {
+                res.append(", ");
+            }
+
+            var k = entry.getKey();
+            var v = entry.getValue();
+
+            res.append(k);
+            res.append('=');
+            res.append(v);
+        }
+
+        res.append("}");
+
+        System.out.println(res);
+    }
+}