CODEWITHSUNDEEP
c#parallel-processing
user3564367
user3564367

Reputation:

AsOrdered() not working

I'm trying use AsParallell() with AsOrdered() method, but always I see unordered results.

using System;
using System.Linq;
using System.Collections.Generic;

namespace Parallel
{
    class MainClass
    {
        public static void Main(string[] args)
        {
            List<String> cities = new List<String>() {
                "Barcelona",
                "Valencia",
                "Sevilla",
                "Zaragoza",
                "Málaga",
                "Murcia",
                "Palma",
                "Las Palmas de Gran Canaria",
                "Alicante",
                "Madrid",
                "Córdoba",
                "Valladolid",
                "Tarrasa",
                "Vigo",
                "Gijón",
                "Cartagena",
                "Hospitalet de Llobregat",
                "Vitoria",
                "La Coruña",
                "Granada",
                "Elche",
                "Oviedo",
                "Badalona"
            };

            var filtered = cities.AsParallel().AsOrdered().Where(c => c.ToUpper().StartsWith("B") || c.ToUpper().EndsWith("A")).ToArray();

            Console.WriteLine("Cities starting with \"B\" or ends with \"A\"");

            foreach (String city in filtered) 
            {
                Console.WriteLine(city);
            }

        }
    }
}

The output is:

Cities starting with "B" or ends with "A"
Barcelona
Valencia
Sevilla
Zaragoza
Málaga
Murcia
Palma
Las Palmas de Gran Canaria
Córdoba
Tarrasa
Cartagena
Vitoria
La Coruña
Granada
Badalona

Press any key to continue...

Whats wrong?

I'm using Visual Studio in Mac, Net Core project.

Thanks

Upvotes: 2

Views: 214

Answers (2)

mm8
mm8

Reputation: 169270

AsOrdered() just maintains the original order of the items in the List<string>. If you want to order the items alphabetically you could use the OrderBy method:

var filtered = cities.AsParallel().Where(c => c.ToUpper().StartsWith("B") || c.ToUpper().EndsWith("A")).OrderBy(x => x).ToArray();

Upvotes: 2

Evk
Evk

Reputation: 101493

AsOrdered does not mean it will sort your collection. AsOrdered means it will preserve existing ordering. Because your collection is initially unordered - your results are unordered too.

If you will do

 cities.Sort();

before parallel query - your results will be ordered. However, if you do this but remove AsParallel - your results are not guaranteed to be ordered.

Upvotes: 0

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