generate.go

package main

import (
	"bufio"
	"fmt"
	"math/rand"
	"os"
	"strconv"
	"time"
)

type WeatherStation struct {
	id       string
	meanTemp float64
}

func (w WeatherStation) measurement(rng *rand.Rand) float64 {
	return rng.NormFloat64()*10 + w.meanTemp
}

var stations = []WeatherStation{
	{"Abha", 18.0},
	{"Abidjan", 26.0},
	{"Abéché", 29.4},
	{"Accra", 26.4},
	{"Addis Ababa", 16.0},
	{"Adelaide", 17.3},
	{"Aden", 29.1},
	{"Ahvaz", 25.4},
	{"Albuquerque", 14.0},
	{"Alexandra", 11.0},
	{"Alexandria", 20.0},
	{"Algiers", 18.2},
	{"Alice Springs", 21.0},
	{"Almaty", 10.0},
	{"Amsterdam", 10.2},
	{"Anadyr", -6.9},
	{"Anchorage", 2.8},
	{"Andorra la Vella", 9.8},
	{"Ankara", 12.0},
	{"Antananarivo", 17.9},
	{"Antsiranana", 25.2},
	{"Arkhangelsk", 1.3},
	{"Ashgabat", 17.1},
	{"Asmara", 15.6},
	{"Assab", 30.5},
	{"Astana", 3.5},
	{"Athens", 19.2},
	{"Atlanta", 17.0},
	{"Auckland", 15.2},
	{"Austin", 20.7},
	{"Baghdad", 22.77},
	{"Baguio", 19.5},
	{"Baku", 15.1},
	{"Baltimore", 13.1},
	{"Bamako", 27.8},
	{"Bangkok", 28.6},
	{"Bangui", 26.0},
	{"Banjul", 26.0},
	{"Barcelona", 18.2},
	{"Bata", 25.1},
	{"Batumi", 14.0},
	{"Beijing", 12.9},
	{"Beirut", 20.9},
	{"Belgrade", 12.5},
	{"Belize City", 26.7},
	{"Benghazi", 19.9},
	{"Bergen", 7.7},
	{"Berlin", 10.3},
	{"Bilbao", 14.7},
	{"Birao", 26.5},
	{"Bishkek", 11.3},
	{"Bissau", 27.0},
	{"Blantyre", 22.2},
	{"Bloemfontein", 15.6},
	{"Boise", 11.4},
	{"Bordeaux", 14.2},
	{"Bosaso", 30.0},
	{"Boston", 10.9},
	{"Bouaké", 26.0},
	{"Bratislava", 10.5},
	{"Brazzaville", 25.0},
	{"Bridgetown", 27.0},
	{"Brisbane", 21.4},
	{"Brussels", 10.5},
	{"Bucharest", 10.8},
	{"Budapest", 11.3},
	{"Bujumbura", 23.8},
	{"Bulawayo", 18.9},
	{"Burnie", 13.1},
	{"Busan", 15.0},
	{"Cabo San Lucas", 23.9},
	{"Cairns", 25.0},
	{"Cairo", 21.4},
	{"Calgary", 4.4},
	{"Canberra", 13.1},
	{"Cape Town", 16.2},
	{"Changsha", 17.4},
	{"Charlotte", 16.1},
	{"Chiang Mai", 25.8},
	{"Chicago", 9.8},
	{"Chihuahua", 18.6},
	{"Chișinău", 10.2},
	{"Chittagong", 25.9},
	{"Chongqing", 18.6},
	{"Christchurch", 12.2},
	{"City of San Marino", 11.8},
	{"Colombo", 27.4},
	{"Columbus", 11.7},
	{"Conakry", 26.4},
	{"Copenhagen", 9.1},
	{"Cotonou", 27.2},
	{"Cracow", 9.3},
	{"Da Lat", 17.9},
	{"Da Nang", 25.8},
	{"Dakar", 24.0},
	{"Dallas", 19.0},
	{"Damascus", 17.0},
	{"Dampier", 26.4},
	{"Dar es Salaam", 25.8},
	{"Darwin", 27.6},
	{"Denpasar", 23.7},
	{"Denver", 10.4},
	{"Detroit", 10.0},
	{"Dhaka", 25.9},
	{"Dikson", -11.1},
	{"Dili", 26.6},
	{"Djibouti", 29.9},
	{"Dodoma", 22.7},
	{"Dolisie", 24.0},
	{"Douala", 26.7},
	{"Dubai", 26.9},
	{"Dublin", 9.8},
	{"Dunedin", 11.1},
	{"Durban", 20.6},
	{"Dushanbe", 14.7},
	{"Edinburgh", 9.3},
	{"Edmonton", 4.2},
	{"El Paso", 18.1},
	{"Entebbe", 21.0},
	{"Erbil", 19.5},
	{"Erzurum", 5.1},
	{"Fairbanks", -2.3},
	{"Fianarantsoa", 17.9},
	{"Flores,  Petén", 26.4},
	{"Frankfurt", 10.6},
	{"Fresno", 17.9},
	{"Fukuoka", 17.0},
	{"Gabès", 19.5},
	{"Gaborone", 21.0},
	{"Gagnoa", 26.0},
	{"Gangtok", 15.2},
	{"Garissa", 29.3},
	{"Garoua", 28.3},
	{"George Town", 27.9},
	{"Ghanzi", 21.4},
	{"Gjoa Haven", -14.4},
	{"Guadalajara", 20.9},
	{"Guangzhou", 22.4},
	{"Guatemala City", 20.4},
	{"Halifax", 7.5},
	{"Hamburg", 9.7},
	{"Hamilton", 13.8},
	{"Hanga Roa", 20.5},
	{"Hanoi", 23.6},
	{"Harare", 18.4},
	{"Harbin", 5.0},
	{"Hargeisa", 21.7},
	{"Hat Yai", 27.0},
	{"Havana", 25.2},
	{"Helsinki", 5.9},
	{"Heraklion", 18.9},
	{"Hiroshima", 16.3},
	{"Ho Chi Minh City", 27.4},
	{"Hobart", 12.7},
	{"Hong Kong", 23.3},
	{"Honiara", 26.5},
	{"Honolulu", 25.4},
	{"Houston", 20.8},
	{"Ifrane", 11.4},
	{"Indianapolis", 11.8},
	{"Iqaluit", -9.3},
	{"Irkutsk", 1.0},
	{"Istanbul", 13.9},
	{"İzmir", 17.9},
	{"Jacksonville", 20.3},
	{"Jakarta", 26.7},
	{"Jayapura", 27.0},
	{"Jerusalem", 18.3},
	{"Johannesburg", 15.5},
	{"Jos", 22.8},
	{"Juba", 27.8},
	{"Kabul", 12.1},
	{"Kampala", 20.0},
	{"Kandi", 27.7},
	{"Kankan", 26.5},
	{"Kano", 26.4},
	{"Kansas City", 12.5},
	{"Karachi", 26.0},
	{"Karonga", 24.4},
	{"Kathmandu", 18.3},
	{"Khartoum", 29.9},
	{"Kingston", 27.4},
	{"Kinshasa", 25.3},
	{"Kolkata", 26.7},
	{"Kuala Lumpur", 27.3},
	{"Kumasi", 26.0},
	{"Kunming", 15.7},
	{"Kuopio", 3.4},
	{"Kuwait City", 25.7},
	{"Kyiv", 8.4},
	{"Kyoto", 15.8},
	{"La Ceiba", 26.2},
	{"La Paz", 23.7},
	{"Lagos", 26.8},
	{"Lahore", 24.3},
	{"Lake Havasu City", 23.7},
	{"Lake Tekapo", 8.7},
	{"Las Palmas de Gran Canaria", 21.2},
	{"Las Vegas", 20.3},
	{"Launceston", 13.1},
	{"Lhasa", 7.6},
	{"Libreville", 25.9},
	{"Lisbon", 17.5},
	{"Livingstone", 21.8},
	{"Ljubljana", 10.9},
	{"Lodwar", 29.3},
	{"Lomé", 26.9},
	{"London", 11.3},
	{"Los Angeles", 18.6},
	{"Louisville", 13.9},
	{"Luanda", 25.8},
	{"Lubumbashi", 20.8},
	{"Lusaka", 19.9},
	{"Luxembourg City", 9.3},
	{"Lviv", 7.8},
	{"Lyon", 12.5},
	{"Madrid", 15.0},
	{"Mahajanga", 26.3},
	{"Makassar", 26.7},
	{"Makurdi", 26.0},
	{"Malabo", 26.3},
	{"Malé", 28.0},
	{"Managua", 27.3},
	{"Manama", 26.5},
	{"Mandalay", 28.0},
	{"Mango", 28.1},
	{"Manila", 28.4},
	{"Maputo", 22.8},
	{"Marrakesh", 19.6},
	{"Marseille", 15.8},
	{"Maun", 22.4},
	{"Medan", 26.5},
	{"Mek'ele", 22.7},
	{"Melbourne", 15.1},
	{"Memphis", 17.2},
	{"Mexicali", 23.1},
	{"Mexico City", 17.5},
	{"Miami", 24.9},
	{"Milan", 13.0},
	{"Milwaukee", 8.9},
	{"Minneapolis", 7.8},
	{"Minsk", 6.7},
	{"Mogadishu", 27.1},
	{"Mombasa", 26.3},
	{"Monaco", 16.4},
	{"Moncton", 6.1},
	{"Monterrey", 22.3},
	{"Montreal", 6.8},
	{"Moscow", 5.8},
	{"Mumbai", 27.1},
	{"Murmansk", 0.6},
	{"Muscat", 28.0},
	{"Mzuzu", 17.7},
	{"N'Djamena", 28.3},
	{"Naha", 23.1},
	{"Nairobi", 17.8},
	{"Nakhon Ratchasima", 27.3},
	{"Napier", 14.6},
	{"Napoli", 15.9},
	{"Nashville", 15.4},
	{"Nassau", 24.6},
	{"Ndola", 20.3},
	{"New Delhi", 25.0},
	{"New Orleans", 20.7},
	{"New York City", 12.9},
	{"Ngaoundéré", 22.0},
	{"Niamey", 29.3},
	{"Nicosia", 19.7},
	{"Niigata", 13.9},
	{"Nouadhibou", 21.3},
	{"Nouakchott", 25.7},
	{"Novosibirsk", 1.7},
	{"Nuuk", -1.4},
	{"Odesa", 10.7},
	{"Odienné", 26.0},
	{"Oklahoma City", 15.9},
	{"Omaha", 10.6},
	{"Oranjestad", 28.1},
	{"Oslo", 5.7},
	{"Ottawa", 6.6},
	{"Ouagadougou", 28.3},
	{"Ouahigouya", 28.6},
	{"Ouarzazate", 18.9},
	{"Oulu", 2.7},
	{"Palembang", 27.3},
	{"Palermo", 18.5},
	{"Palm Springs", 24.5},
	{"Palmerston North", 13.2},
	{"Panama City", 28.0},
	{"Parakou", 26.8},
	{"Paris", 12.3},
	{"Perth", 18.7},
	{"Petropavlovsk-Kamchatsky", 1.9},
	{"Philadelphia", 13.2},
	{"Phnom Penh", 28.3},
	{"Phoenix", 23.9},
	{"Pittsburgh", 10.8},
	{"Podgorica", 15.3},
	{"Pointe-Noire", 26.1},
	{"Pontianak", 27.7},
	{"Port Moresby", 26.9},
	{"Port Sudan", 28.4},
	{"Port Vila", 24.3},
	{"Port-Gentil", 26.0},
	{"Portland (OR)", 12.4},
	{"Porto", 15.7},
	{"Prague", 8.4},
	{"Praia", 24.4},
	{"Pretoria", 18.2},
	{"Pyongyang", 10.8},
	{"Rabat", 17.2},
	{"Rangpur", 24.4},
	{"Reggane", 28.3},
	{"Reykjavík", 4.3},
	{"Riga", 6.2},
	{"Riyadh", 26.0},
	{"Rome", 15.2},
	{"Roseau", 26.2},
	{"Rostov-on-Don", 9.9},
	{"Sacramento", 16.3},
	{"Saint Petersburg", 5.8},
	{"Saint-Pierre", 5.7},
	{"Salt Lake City", 11.6},
	{"San Antonio", 20.8},
	{"San Diego", 17.8},
	{"San Francisco", 14.6},
	{"San Jose", 16.4},
	{"San José", 22.6},
	{"San Juan", 27.2},
	{"San Salvador", 23.1},
	{"Sana'a", 20.0},
	{"Santo Domingo", 25.9},
	{"Sapporo", 8.9},
	{"Sarajevo", 10.1},
	{"Saskatoon", 3.3},
	{"Seattle", 11.3},
	{"Ségou", 28.0},
	{"Seoul", 12.5},
	{"Seville", 19.2},
	{"Shanghai", 16.7},
	{"Singapore", 27.0},
	{"Skopje", 12.4},
	{"Sochi", 14.2},
	{"Sofia", 10.6},
	{"Sokoto", 28.0},
	{"Split", 16.1},
	{"St. John's", 5.0},
	{"St. Louis", 13.9},
	{"Stockholm", 6.6},
	{"Surabaya", 27.1},
	{"Suva", 25.6},
	{"Suwałki", 7.2},
	{"Sydney", 17.7},
	{"Tabora", 23.0},
	{"Tabriz", 12.6},
	{"Taipei", 23.0},
	{"Tallinn", 6.4},
	{"Tamale", 27.9},
	{"Tamanrasset", 21.7},
	{"Tampa", 22.9},
	{"Tashkent", 14.8},
	{"Tauranga", 14.8},
	{"Tbilisi", 12.9},
	{"Tegucigalpa", 21.7},
	{"Tehran", 17.0},
	{"Tel Aviv", 20.0},
	{"Thessaloniki", 16.0},
	{"Thiès", 24.0},
	{"Tijuana", 17.8},
	{"Timbuktu", 28.0},
	{"Tirana", 15.2},
	{"Toamasina", 23.4},
	{"Tokyo", 15.4},
	{"Toliara", 24.1},
	{"Toluca", 12.4},
	{"Toronto", 9.4},
	{"Tripoli", 20.0},
	{"Tromsø", 2.9},
	{"Tucson", 20.9},
	{"Tunis", 18.4},
	{"Ulaanbaatar", -0.4},
	{"Upington", 20.4},
	{"Ürümqi", 7.4},
	{"Vaduz", 10.1},
	{"Valencia", 18.3},
	{"Valletta", 18.8},
	{"Vancouver", 10.4},
	{"Veracruz", 25.4},
	{"Vienna", 10.4},
	{"Vientiane", 25.9},
	{"Villahermosa", 27.1},
	{"Vilnius", 6.0},
	{"Virginia Beach", 15.8},
	{"Vladivostok", 4.9},
	{"Warsaw", 8.5},
	{"Washington, D.C.", 14.6},
	{"Wau", 27.8},
	{"Wellington", 12.9},
	{"Whitehorse", -0.1},
	{"Wichita", 13.9},
	{"Willemstad", 28.0},
	{"Winnipeg", 3.0},
	{"Wrocław", 9.6},
	{"Xi'an", 14.1},
	{"Yakutsk", -8.8},
	{"Yangon", 27.5},
	{"Yaoundé", 23.8},
	{"Yellowknife", -4.3},
	{"Yerevan", 12.4},
	{"Yinchuan", 9.0},
	{"Zagreb", 10.7},
	{"Zanzibar City", 26.0},
	{"Zürich", 9.3},
}

func main() {
	start := time.Now()
	f, err := os.Create("measurements.txt")
	if err != nil {
		panic(err)
	}
	defer func() {
		err := f.Close()
		if err != nil {
			panic(err)
		}
	}()

	size, err := strconv.ParseInt(os.Args[1], 10, 64)
	if err != nil {
		panic(err)
	}

	w := bufio.NewWriterSize(f, 512<<10 /* 512 KB */)
	rng := rand.New(rand.NewSource(time.Now().UnixNano()))
	for i := int64(0); i < size; i++ {
		if i > 0 && i%50_000_000 == 0 {
			fmt.Printf("Wrote %d measurements in %d ms\n", i, time.Now().Sub(start).Milliseconds())
		}
		s := stations[rng.Intn(len(stations))]
		_, err := fmt.Fprintf(w, "%s;%.1f\n", s.id, s.measurement(rng))
		if err != nil {
			panic(err)
		}
	}
	if err = w.Flush(); err != nil {
		panic(err)
	}
}