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-rw-r--r--src/main/java/dev/morling/onebrc/CreateMeasurementsFast.java537
1 files changed, 537 insertions, 0 deletions
diff --git a/src/main/java/dev/morling/onebrc/CreateMeasurementsFast.java b/src/main/java/dev/morling/onebrc/CreateMeasurementsFast.java
new file mode 100644
index 0000000..895e359
--- /dev/null
+++ b/src/main/java/dev/morling/onebrc/CreateMeasurementsFast.java
@@ -0,0 +1,537 @@
+/*
+ * 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.BufferedWriter;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardOpenOption;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executor;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ThreadLocalRandom;
+
+public class CreateMeasurementsFast {
+
+ private static final Path MEASUREMENT_FILE = Path.of("./measurements.txt");
+ static final Executor EXECUTOR_SERVICE = Executors.newWorkStealingPool();
+
+ private record WeatherStation(String id, double meanTemperature) {
+ double measurement() {
+ double m = ThreadLocalRandom.current().nextGaussian(meanTemperature, 10);
+ return Math.round(m * 10.0) / 10.0;
+ }
+ }
+
+ public static void main(String[] args) throws Exception {
+ long start = System.currentTimeMillis();
+
+ if (args.length != 1) {
+ System.out.println("Usage: create_measurements.sh <number of records to create>");
+ System.exit(1);
+ }
+
+ int size = 0;
+ try {
+ size = Integer.parseInt(args[0]);
+ }
+ catch (NumberFormatException e) {
+ System.out.println("Invalid value for <number of records to create>");
+ System.out.println("Usage: CreateMeasurements <number of records to create>");
+ System.exit(1);
+ }
+
+ try {
+ Files.deleteIfExists(MEASUREMENT_FILE);
+ Files.createFile(MEASUREMENT_FILE);
+ }
+ catch (Exception e) {
+ // ignore
+ }
+
+ // @formatter:off
+ // data from https://en.wikipedia.org/wiki/List_of_cities_by_average_temperature;
+ // converted using https://wikitable2csv.ggor.de/
+ // brought to form using DuckDB:
+ // D copy (
+ // select City, regexp_extract(Year,'(.*)\n.*', 1) as AverageTemp
+ // from (
+ // select City,Year
+ // from read_csv_auto('List_of_cities_by_average_temperature_1.csv', header = true)
+ // union
+ // select City,Year
+ // from read_csv_auto('List_of_cities_by_average_temperature_2.csv', header = true)
+ // union
+ // select City,Year
+ // from read_csv_auto('List_of_cities_by_average_temperature_3.csv', header = true)
+ // union
+ // select City,Year
+ // from read_csv_auto('List_of_cities_by_average_temperature_4.csv', header = true)
+ // union
+ // select City,Year
+ // from read_csv_auto('List_of_cities_by_average_temperature_5.csv', header = true)
+ // )
+ // ) TO 'output.csv' (HEADER, DELIMITER ',');
+ // @formatter:on
+ List<WeatherStation> stations = List.of(
+ new WeatherStation("Abha", 18.0),
+ new WeatherStation("Abidjan", 26.0),
+ new WeatherStation("Abéché", 29.4),
+ new WeatherStation("Accra", 26.4),
+ new WeatherStation("Addis Ababa", 16.0),
+ new WeatherStation("Adelaide", 17.3),
+ new WeatherStation("Aden", 29.1),
+ new WeatherStation("Ahvaz", 25.4),
+ new WeatherStation("Albuquerque", 14.0),
+ new WeatherStation("Alexandra", 11.0),
+ new WeatherStation("Alexandria", 20.0),
+ new WeatherStation("Algiers", 18.2),
+ new WeatherStation("Alice Springs", 21.0),
+ new WeatherStation("Almaty", 10.0),
+ new WeatherStation("Amsterdam", 10.2),
+ new WeatherStation("Anadyr", -6.9),
+ new WeatherStation("Anchorage", 2.8),
+ new WeatherStation("Andorra la Vella", 9.8),
+ new WeatherStation("Ankara", 12.0),
+ new WeatherStation("Antananarivo", 17.9),
+ new WeatherStation("Antsiranana", 25.2),
+ new WeatherStation("Arkhangelsk", 1.3),
+ new WeatherStation("Ashgabat", 17.1),
+ new WeatherStation("Asmara", 15.6),
+ new WeatherStation("Assab", 30.5),
+ new WeatherStation("Astana", 3.5),
+ new WeatherStation("Athens", 19.2),
+ new WeatherStation("Atlanta", 17.0),
+ new WeatherStation("Auckland", 15.2),
+ new WeatherStation("Austin", 20.7),
+ new WeatherStation("Baghdad", 22.77),
+ new WeatherStation("Baguio", 19.5),
+ new WeatherStation("Baku", 15.1),
+ new WeatherStation("Baltimore", 13.1),
+ new WeatherStation("Bamako", 27.8),
+ new WeatherStation("Bangkok", 28.6),
+ new WeatherStation("Bangui", 26.0),
+ new WeatherStation("Banjul", 26.0),
+ new WeatherStation("Barcelona", 18.2),
+ new WeatherStation("Bata", 25.1),
+ new WeatherStation("Batumi", 14.0),
+ new WeatherStation("Beijing", 12.9),
+ new WeatherStation("Beirut", 20.9),
+ new WeatherStation("Belgrade", 12.5),
+ new WeatherStation("Belize City", 26.7),
+ new WeatherStation("Benghazi", 19.9),
+ new WeatherStation("Bergen", 7.7),
+ new WeatherStation("Berlin", 10.3),
+ new WeatherStation("Bilbao", 14.7),
+ new WeatherStation("Birao", 26.5),
+ new WeatherStation("Bishkek", 11.3),
+ new WeatherStation("Bissau", 27.0),
+ new WeatherStation("Blantyre", 22.2),
+ new WeatherStation("Bloemfontein", 15.6),
+ new WeatherStation("Boise", 11.4),
+ new WeatherStation("Bordeaux", 14.2),
+ new WeatherStation("Bosaso", 30.0),
+ new WeatherStation("Boston", 10.9),
+ new WeatherStation("Bouaké", 26.0),
+ new WeatherStation("Bratislava", 10.5),
+ new WeatherStation("Brazzaville", 25.0),
+ new WeatherStation("Bridgetown", 27.0),
+ new WeatherStation("Brisbane", 21.4),
+ new WeatherStation("Brussels", 10.5),
+ new WeatherStation("Bucharest", 10.8),
+ new WeatherStation("Budapest", 11.3),
+ new WeatherStation("Bujumbura", 23.8),
+ new WeatherStation("Bulawayo", 18.9),
+ new WeatherStation("Burnie", 13.1),
+ new WeatherStation("Busan", 15.0),
+ new WeatherStation("Cabo San Lucas", 23.9),
+ new WeatherStation("Cairns", 25.0),
+ new WeatherStation("Cairo", 21.4),
+ new WeatherStation("Calgary", 4.4),
+ new WeatherStation("Canberra", 13.1),
+ new WeatherStation("Cape Town", 16.2),
+ new WeatherStation("Changsha", 17.4),
+ new WeatherStation("Charlotte", 16.1),
+ new WeatherStation("Chiang Mai", 25.8),
+ new WeatherStation("Chicago", 9.8),
+ new WeatherStation("Chihuahua", 18.6),
+ new WeatherStation("Chișinău", 10.2),
+ new WeatherStation("Chittagong", 25.9),
+ new WeatherStation("Chongqing", 18.6),
+ new WeatherStation("Christchurch", 12.2),
+ new WeatherStation("City of San Marino", 11.8),
+ new WeatherStation("Colombo", 27.4),
+ new WeatherStation("Columbus", 11.7),
+ new WeatherStation("Conakry", 26.4),
+ new WeatherStation("Copenhagen", 9.1),
+ new WeatherStation("Cotonou", 27.2),
+ new WeatherStation("Cracow", 9.3),
+ new WeatherStation("Da Lat", 17.9),
+ new WeatherStation("Da Nang", 25.8),
+ new WeatherStation("Dakar", 24.0),
+ new WeatherStation("Dallas", 19.0),
+ new WeatherStation("Damascus", 17.0),
+ new WeatherStation("Dampier", 26.4),
+ new WeatherStation("Dar es Salaam", 25.8),
+ new WeatherStation("Darwin", 27.6),
+ new WeatherStation("Denpasar", 23.7),
+ new WeatherStation("Denver", 10.4),
+ new WeatherStation("Detroit", 10.0),
+ new WeatherStation("Dhaka", 25.9),
+ new WeatherStation("Dikson", -11.1),
+ new WeatherStation("Dili", 26.6),
+ new WeatherStation("Djibouti", 29.9),
+ new WeatherStation("Dodoma", 22.7),
+ new WeatherStation("Dolisie", 24.0),
+ new WeatherStation("Douala", 26.7),
+ new WeatherStation("Dubai", 26.9),
+ new WeatherStation("Dublin", 9.8),
+ new WeatherStation("Dunedin", 11.1),
+ new WeatherStation("Durban", 20.6),
+ new WeatherStation("Dushanbe", 14.7),
+ new WeatherStation("Edinburgh", 9.3),
+ new WeatherStation("Edmonton", 4.2),
+ new WeatherStation("El Paso", 18.1),
+ new WeatherStation("Entebbe", 21.0),
+ new WeatherStation("Erbil", 19.5),
+ new WeatherStation("Erzurum", 5.1),
+ new WeatherStation("Fairbanks", -2.3),
+ new WeatherStation("Fianarantsoa", 17.9),
+ new WeatherStation("Flores, Petén", 26.4),
+ new WeatherStation("Frankfurt", 10.6),
+ new WeatherStation("Fresno", 17.9),
+ new WeatherStation("Fukuoka", 17.0),
+ new WeatherStation("Gabès", 19.5),
+ new WeatherStation("Gaborone", 21.0),
+ new WeatherStation("Gagnoa", 26.0),
+ new WeatherStation("Gangtok", 15.2),
+ new WeatherStation("Garissa", 29.3),
+ new WeatherStation("Garoua", 28.3),
+ new WeatherStation("George Town", 27.9),
+ new WeatherStation("Ghanzi", 21.4),
+ new WeatherStation("Gjoa Haven", -14.4),
+ new WeatherStation("Guadalajara", 20.9),
+ new WeatherStation("Guangzhou", 22.4),
+ new WeatherStation("Guatemala City", 20.4),
+ new WeatherStation("Halifax", 7.5),
+ new WeatherStation("Hamburg", 9.7),
+ new WeatherStation("Hamilton", 13.8),
+ new WeatherStation("Hanga Roa", 20.5),
+ new WeatherStation("Hanoi", 23.6),
+ new WeatherStation("Harare", 18.4),
+ new WeatherStation("Harbin", 5.0),
+ new WeatherStation("Hargeisa", 21.7),
+ new WeatherStation("Hat Yai", 27.0),
+ new WeatherStation("Havana", 25.2),
+ new WeatherStation("Helsinki", 5.9),
+ new WeatherStation("Heraklion", 18.9),
+ new WeatherStation("Hiroshima", 16.3),
+ new WeatherStation("Ho Chi Minh City", 27.4),
+ new WeatherStation("Hobart", 12.7),
+ new WeatherStation("Hong Kong", 23.3),
+ new WeatherStation("Honiara", 26.5),
+ new WeatherStation("Honolulu", 25.4),
+ new WeatherStation("Houston", 20.8),
+ new WeatherStation("Ifrane", 11.4),
+ new WeatherStation("Indianapolis", 11.8),
+ new WeatherStation("Iqaluit", -9.3),
+ new WeatherStation("Irkutsk", 1.0),
+ new WeatherStation("Istanbul", 13.9),
+ new WeatherStation("İzmir", 17.9),
+ new WeatherStation("Jacksonville", 20.3),
+ new WeatherStation("Jakarta", 26.7),
+ new WeatherStation("Jayapura", 27.0),
+ new WeatherStation("Jerusalem", 18.3),
+ new WeatherStation("Johannesburg", 15.5),
+ new WeatherStation("Jos", 22.8),
+ new WeatherStation("Juba", 27.8),
+ new WeatherStation("Kabul", 12.1),
+ new WeatherStation("Kampala", 20.0),
+ new WeatherStation("Kandi", 27.7),
+ new WeatherStation("Kankan", 26.5),
+ new WeatherStation("Kano", 26.4),
+ new WeatherStation("Kansas City", 12.5),
+ new WeatherStation("Karachi", 26.0),
+ new WeatherStation("Karonga", 24.4),
+ new WeatherStation("Kathmandu", 18.3),
+ new WeatherStation("Khartoum", 29.9),
+ new WeatherStation("Kingston", 27.4),
+ new WeatherStation("Kinshasa", 25.3),
+ new WeatherStation("Kolkata", 26.7),
+ new WeatherStation("Kuala Lumpur", 27.3),
+ new WeatherStation("Kumasi", 26.0),
+ new WeatherStation("Kunming", 15.7),
+ new WeatherStation("Kuopio", 3.4),
+ new WeatherStation("Kuwait City", 25.7),
+ new WeatherStation("Kyiv", 8.4),
+ new WeatherStation("Kyoto", 15.8),
+ new WeatherStation("La Ceiba", 26.2),
+ new WeatherStation("La Paz", 23.7),
+ new WeatherStation("Lagos", 26.8),
+ new WeatherStation("Lahore", 24.3),
+ new WeatherStation("Lake Havasu City", 23.7),
+ new WeatherStation("Lake Tekapo", 8.7),
+ new WeatherStation("Las Palmas de Gran Canaria", 21.2),
+ new WeatherStation("Las Vegas", 20.3),
+ new WeatherStation("Launceston", 13.1),
+ new WeatherStation("Lhasa", 7.6),
+ new WeatherStation("Libreville", 25.9),
+ new WeatherStation("Lisbon", 17.5),
+ new WeatherStation("Livingstone", 21.8),
+ new WeatherStation("Ljubljana", 10.9),
+ new WeatherStation("Lodwar", 29.3),
+ new WeatherStation("Lomé", 26.9),
+ new WeatherStation("London", 11.3),
+ new WeatherStation("Los Angeles", 18.6),
+ new WeatherStation("Louisville", 13.9),
+ new WeatherStation("Luanda", 25.8),
+ new WeatherStation("Lubumbashi", 20.8),
+ new WeatherStation("Lusaka", 19.9),
+ new WeatherStation("Luxembourg City", 9.3),
+ new WeatherStation("Lviv", 7.8),
+ new WeatherStation("Lyon", 12.5),
+ new WeatherStation("Madrid", 15.0),
+ new WeatherStation("Mahajanga", 26.3),
+ new WeatherStation("Makassar", 26.7),
+ new WeatherStation("Makurdi", 26.0),
+ new WeatherStation("Malabo", 26.3),
+ new WeatherStation("Malé", 28.0),
+ new WeatherStation("Managua", 27.3),
+ new WeatherStation("Manama", 26.5),
+ new WeatherStation("Mandalay", 28.0),
+ new WeatherStation("Mango", 28.1),
+ new WeatherStation("Manila", 28.4),
+ new WeatherStation("Maputo", 22.8),
+ new WeatherStation("Marrakesh", 19.6),
+ new WeatherStation("Marseille", 15.8),
+ new WeatherStation("Maun", 22.4),
+ new WeatherStation("Medan", 26.5),
+ new WeatherStation("Mek'ele", 22.7),
+ new WeatherStation("Melbourne", 15.1),
+ new WeatherStation("Memphis", 17.2),
+ new WeatherStation("Mexicali", 23.1),
+ new WeatherStation("Mexico City", 17.5),
+ new WeatherStation("Miami", 24.9),
+ new WeatherStation("Milan", 13.0),
+ new WeatherStation("Milwaukee", 8.9),
+ new WeatherStation("Minneapolis", 7.8),
+ new WeatherStation("Minsk", 6.7),
+ new WeatherStation("Mogadishu", 27.1),
+ new WeatherStation("Mombasa", 26.3),
+ new WeatherStation("Monaco", 16.4),
+ new WeatherStation("Moncton", 6.1),
+ new WeatherStation("Monterrey", 22.3),
+ new WeatherStation("Montreal", 6.8),
+ new WeatherStation("Moscow", 5.8),
+ new WeatherStation("Mumbai", 27.1),
+ new WeatherStation("Murmansk", 0.6),
+ new WeatherStation("Muscat", 28.0),
+ new WeatherStation("Mzuzu", 17.7),
+ new WeatherStation("N'Djamena", 28.3),
+ new WeatherStation("Naha", 23.1),
+ new WeatherStation("Nairobi", 17.8),
+ new WeatherStation("Nakhon Ratchasima", 27.3),
+ new WeatherStation("Napier", 14.6),
+ new WeatherStation("Napoli", 15.9),
+ new WeatherStation("Nashville", 15.4),
+ new WeatherStation("Nassau", 24.6),
+ new WeatherStation("Ndola", 20.3),
+ new WeatherStation("New Delhi", 25.0),
+ new WeatherStation("New Orleans", 20.7),
+ new WeatherStation("New York City", 12.9),
+ new WeatherStation("Ngaoundéré", 22.0),
+ new WeatherStation("Niamey", 29.3),
+ new WeatherStation("Nicosia", 19.7),
+ new WeatherStation("Niigata", 13.9),
+ new WeatherStation("Nouadhibou", 21.3),
+ new WeatherStation("Nouakchott", 25.7),
+ new WeatherStation("Novosibirsk", 1.7),
+ new WeatherStation("Nuuk", -1.4),
+ new WeatherStation("Odesa", 10.7),
+ new WeatherStation("Odienné", 26.0),
+ new WeatherStation("Oklahoma City", 15.9),
+ new WeatherStation("Omaha", 10.6),
+ new WeatherStation("Oranjestad", 28.1),
+ new WeatherStation("Oslo", 5.7),
+ new WeatherStation("Ottawa", 6.6),
+ new WeatherStation("Ouagadougou", 28.3),
+ new WeatherStation("Ouahigouya", 28.6),
+ new WeatherStation("Ouarzazate", 18.9),
+ new WeatherStation("Oulu", 2.7),
+ new WeatherStation("Palembang", 27.3),
+ new WeatherStation("Palermo", 18.5),
+ new WeatherStation("Palm Springs", 24.5),
+ new WeatherStation("Palmerston North", 13.2),
+ new WeatherStation("Panama City", 28.0),
+ new WeatherStation("Parakou", 26.8),
+ new WeatherStation("Paris", 12.3),
+ new WeatherStation("Perth", 18.7),
+ new WeatherStation("Petropavlovsk-Kamchatsky", 1.9),
+ new WeatherStation("Philadelphia", 13.2),
+ new WeatherStation("Phnom Penh", 28.3),
+ new WeatherStation("Phoenix", 23.9),
+ new WeatherStation("Pittsburgh", 10.8),
+ new WeatherStation("Podgorica", 15.3),
+ new WeatherStation("Pointe-Noire", 26.1),
+ new WeatherStation("Pontianak", 27.7),
+ new WeatherStation("Port Moresby", 26.9),
+ new WeatherStation("Port Sudan", 28.4),
+ new WeatherStation("Port Vila", 24.3),
+ new WeatherStation("Port-Gentil", 26.0),
+ new WeatherStation("Portland (OR)", 12.4),
+ new WeatherStation("Porto", 15.7),
+ new WeatherStation("Prague", 8.4),
+ new WeatherStation("Praia", 24.4),
+ new WeatherStation("Pretoria", 18.2),
+ new WeatherStation("Pyongyang", 10.8),
+ new WeatherStation("Rabat", 17.2),
+ new WeatherStation("Rangpur", 24.4),
+ new WeatherStation("Reggane", 28.3),
+ new WeatherStation("Reykjavík", 4.3),
+ new WeatherStation("Riga", 6.2),
+ new WeatherStation("Riyadh", 26.0),
+ new WeatherStation("Rome", 15.2),
+ new WeatherStation("Roseau", 26.2),
+ new WeatherStation("Rostov-on-Don", 9.9),
+ new WeatherStation("Sacramento", 16.3),
+ new WeatherStation("Saint Petersburg", 5.8),
+ new WeatherStation("Saint-Pierre", 5.7),
+ new WeatherStation("Salt Lake City", 11.6),
+ new WeatherStation("San Antonio", 20.8),
+ new WeatherStation("San Diego", 17.8),
+ new WeatherStation("San Francisco", 14.6),
+ new WeatherStation("San Jose", 16.4),
+ new WeatherStation("San José", 22.6),
+ new WeatherStation("San Juan", 27.2),
+ new WeatherStation("San Salvador", 23.1),
+ new WeatherStation("Sana'a", 20.0),
+ new WeatherStation("Santo Domingo", 25.9),
+ new WeatherStation("Sapporo", 8.9),
+ new WeatherStation("Sarajevo", 10.1),
+ new WeatherStation("Saskatoon", 3.3),
+ new WeatherStation("Seattle", 11.3),
+ new WeatherStation("Ségou", 28.0),
+ new WeatherStation("Seoul", 12.5),
+ new WeatherStation("Seville", 19.2),
+ new WeatherStation("Shanghai", 16.7),
+ new WeatherStation("Singapore", 27.0),
+ new WeatherStation("Skopje", 12.4),
+ new WeatherStation("Sochi", 14.2),
+ new WeatherStation("Sofia", 10.6),
+ new WeatherStation("Sokoto", 28.0),
+ new WeatherStation("Split", 16.1),
+ new WeatherStation("St. John's", 5.0),
+ new WeatherStation("St. Louis", 13.9),
+ new WeatherStation("Stockholm", 6.6),
+ new WeatherStation("Surabaya", 27.1),
+ new WeatherStation("Suva", 25.6),
+ new WeatherStation("Suwałki", 7.2),
+ new WeatherStation("Sydney", 17.7),
+ new WeatherStation("Tabora", 23.0),
+ new WeatherStation("Tabriz", 12.6),
+ new WeatherStation("Taipei", 23.0),
+ new WeatherStation("Tallinn", 6.4),
+ new WeatherStation("Tamale", 27.9),
+ new WeatherStation("Tamanrasset", 21.7),
+ new WeatherStation("Tampa", 22.9),
+ new WeatherStation("Tashkent", 14.8),
+ new WeatherStation("Tauranga", 14.8),
+ new WeatherStation("Tbilisi", 12.9),
+ new WeatherStation("Tegucigalpa", 21.7),
+ new WeatherStation("Tehran", 17.0),
+ new WeatherStation("Tel Aviv", 20.0),
+ new WeatherStation("Thessaloniki", 16.0),
+ new WeatherStation("Thiès", 24.0),
+ new WeatherStation("Tijuana", 17.8),
+ new WeatherStation("Timbuktu", 28.0),
+ new WeatherStation("Tirana", 15.2),
+ new WeatherStation("Toamasina", 23.4),
+ new WeatherStation("Tokyo", 15.4),
+ new WeatherStation("Toliara", 24.1),
+ new WeatherStation("Toluca", 12.4),
+ new WeatherStation("Toronto", 9.4),
+ new WeatherStation("Tripoli", 20.0),
+ new WeatherStation("Tromsø", 2.9),
+ new WeatherStation("Tucson", 20.9),
+ new WeatherStation("Tunis", 18.4),
+ new WeatherStation("Ulaanbaatar", -0.4),
+ new WeatherStation("Upington", 20.4),
+ new WeatherStation("Ürümqi", 7.4),
+ new WeatherStation("Vaduz", 10.1),
+ new WeatherStation("Valencia", 18.3),
+ new WeatherStation("Valletta", 18.8),
+ new WeatherStation("Vancouver", 10.4),
+ new WeatherStation("Veracruz", 25.4),
+ new WeatherStation("Vienna", 10.4),
+ new WeatherStation("Vientiane", 25.9),
+ new WeatherStation("Villahermosa", 27.1),
+ new WeatherStation("Vilnius", 6.0),
+ new WeatherStation("Virginia Beach", 15.8),
+ new WeatherStation("Vladivostok", 4.9),
+ new WeatherStation("Warsaw", 8.5),
+ new WeatherStation("Washington, D.C.", 14.6),
+ new WeatherStation("Wau", 27.8),
+ new WeatherStation("Wellington", 12.9),
+ new WeatherStation("Whitehorse", -0.1),
+ new WeatherStation("Wichita", 13.9),
+ new WeatherStation("Willemstad", 28.0),
+ new WeatherStation("Winnipeg", 3.0),
+ new WeatherStation("Wrocław", 9.6),
+ new WeatherStation("Xi'an", 14.1),
+ new WeatherStation("Yakutsk", -8.8),
+ new WeatherStation("Yangon", 27.5),
+ new WeatherStation("Yaoundé", 23.8),
+ new WeatherStation("Yellowknife", -4.3),
+ new WeatherStation("Yerevan", 12.4),
+ new WeatherStation("Yinchuan", 9.0),
+ new WeatherStation("Zagreb", 10.7),
+ new WeatherStation("Zanzibar City", 26.0),
+ new WeatherStation("Zürich", 9.3));
+
+ int chunkSize = (size / 10_000_000) == 0 ? size : 10_000_000;
+ int numberOfFutures = size / chunkSize;
+ if (numberOfFutures == 0) {
+ numberOfFutures = 1;
+ }
+ CompletableFuture<?>[] futures = new CompletableFuture[numberOfFutures];
+
+ for (int n = 0; n < numberOfFutures; n++) {
+ int finalN = n;
+ futures[n] = CompletableFuture.runAsync(() -> {
+ StringBuilder builder = new StringBuilder();
+ for (int i = finalN * chunkSize; i <= (finalN + 1) * chunkSize - 1; i++) {
+ WeatherStation station = stations.get(ThreadLocalRandom.current().nextInt(stations.size()));
+ builder.append(station.id())
+ .append(";")
+ .append(station.measurement())
+ .append('\n');
+ }
+ try (BufferedWriter bw = Files.newBufferedWriter(MEASUREMENT_FILE, StandardOpenOption.APPEND)) {
+ bw.write(builder.toString());
+ }
+ catch (IOException e) {
+ throw new RuntimeException(e);
+ }
+ }, EXECUTOR_SERVICE);
+ }
+
+ CompletableFuture.allOf(futures).join();
+
+ System.out.printf("Created file with %,d measurements in %s ms%n", size, System.currentTimeMillis() - start);
+ }
+}
generated by cgit v1.2.3 (git 2.25.1) at 2026-05-13 14:04:38 +0000