Parallelised code works best when data is not shared. This example shows a simple piece of parallel code where each task operates independently on its own object graph without dependencies on other objects outside its own graph.
Each iteration of the Parallel.ForEach statement operates on only one item in the List named initialObjectGraph. The operations do not make reference to any other objects in the list. The PopulateDetails method (which effectively operates on each item in the list) only uses and updates the information in just that one item.
The program outputs the initial object graph with just the very basic information that is input into it in the GetObjectGraph method. After the Parallel.ForEach has called PopulateDetails on each element in the list, the object graph is output once again
Example Code
class Program
{
static void Main(string[] args)
{
List<HotelRoomAvailability> initialObjectGraph = GetObjectGraph();
DisplayObjectGraph(initialObjectGraph);
Parallel.ForEach(initialObjectGraph, item => PopulateDetails(item));
DisplayObjectGraph(initialObjectGraph);
Console.WriteLine("Program finished");
Console.ReadLine();
}
private static void PopulateDetails(HotelRoomAvailability hotel)
{
Console.WriteLine("Populating details of {0}", hotel.HotelCode);
hotel.Name = HotelRespository.GetHotelName(hotel.HotelCode);
hotel.Rates = AvailabilityRespository.GetRateInformation(
hotel.HotelCode, hotel.StayDate, hotel.NumberOfNights);
}
private static List<HotelRoomAvailability> GetObjectGraph()
{
List<HotelRoomAvailability> result = new List
{
new HotelRoomAvailability
{
StayDate = new DateTime(2011, 7, 1),
NumberOfNights = 3,
HotelCode = "LONSOHO"
},
new HotelRoomAvailability
{
StayDate = new DateTime(2011, 7, 1),
NumberOfNights = 3,
HotelCode = "LONCOVGDN"
},
new HotelRoomAvailability
{
StayDate = new DateTime(2011, 7, 1),
NumberOfNights = 3,
HotelCode = "LONLEISQR"
},
new HotelRoomAvailability
{
StayDate = new DateTime(2011, 7, 1),
NumberOfNights = 3,
HotelCode = "LONHIGHOL"
},
new HotelRoomAvailability
{
StayDate = new DateTime(2011, 7, 1),
NumberOfNights = 3,
HotelCode = "LONKINGSX"
},
new HotelRoomAvailability
{
StayDate = new DateTime(2011, 7, 1),
NumberOfNights = 3,
HotelCode = "LONEUSTON"
}
};
return result;
}
private static void DisplayObjectGraph(
IEnumerable initialObjectGraph)
{
foreach (HotelRoomAvailability availability in initialObjectGraph)
{
Console.WriteLine(availability);
Console.WriteLine(new string('=', 80));
}
}
}
Note that not all code is being shown here. There are a number of classes outside the Program class that operate on the data simulated calls to services or other calculations on the data. If you want to see the full example please download the full code sample using the link at the bottom of this post.
Example output
LONSOHO : Staying on 01/Jul/2011 for 3 nights ================================================================================ LONCOVGDN : Staying on 01/Jul/2011 for 3 nights ================================================================================ LONLEISQR : Staying on 01/Jul/2011 for 3 nights ================================================================================ LONHIGHOL : Staying on 01/Jul/2011 for 3 nights ================================================================================ LONKINGSX : Staying on 01/Jul/2011 for 3 nights ================================================================================ LONEUSTON : Staying on 01/Jul/2011 for 3 nights ================================================================================ Populating details of LONSOHO Populating details of LONCOVGDN Populating details of LONLEISQR Populating details of LONHIGHOL Populating details of LONKINGSX Populating details of LONEUSTON LONSOHO : London Soho Staying on 01/Jul/2011 for 3 nights Available Rates: Rate: One Month Advanced Rate Room Only 01/Jul/2011: £48.40 02/Jul/2011: £52.80 03/Jul/2011: £44.00 Total Price: £145.20 ---------------------------------------- Rate: One Month Advanced Rate Bed and Breakfast 01/Jul/2011: £58.40 02/Jul/2011: £62.80 03/Jul/2011: £54.00 Total Price: £175.20 ---------------------------------------- Rate: One Month Advanced Rate Dinner, Bed and Breakfast 01/Jul/2011: £83.40 02/Jul/2011: £87.80 03/Jul/2011: £79.00 Total Price: £250.20 ---------------------------------------- Rate: Two Week Advances Rate Room Only 01/Jul/2011: £54.45 02/Jul/2011: £59.40 03/Jul/2011: £49.50 Total Price: £163.35 ---------------------------------------- Rate: Two Week Advances Rate Bed and Breakfast 01/Jul/2011: £64.45 02/Jul/2011: £69.40 03/Jul/2011: £59.50 Total Price: £193.35 ---------------------------------------- Rate: Two Week Advances Rate Dinner, Bed and Breakfast 01/Jul/2011: £89.45 02/Jul/2011: £94.40 03/Jul/2011: £84.50 Total Price: £268.35 ---------------------------------------- Rate: Fully Flexible Rate Room Only 01/Jul/2011: £60.50 02/Jul/2011: £66.00 03/Jul/2011: £55.00 Total Price: £181.50 ---------------------------------------- Rate: Fully Flexible Rate Bed and Breakfast 01/Jul/2011: £70.50 02/Jul/2011: £76.00 03/Jul/2011: £65.00 Total Price: £211.50 ---------------------------------------- Rate: Fully Flexible Rate Dinner, Bed and Breakfast 01/Jul/2011: £95.50 02/Jul/2011: £101.00 03/Jul/2011: £90.00 Total Price: £286.50 ---------------------------------------- ================================================================================ LONCOVGDN : London Covent Garden Staying on 01/Jul/2011 for 3 nights Available Rates: Rate: One Month Advanced Rate Room Only 01/Jul/2011: £59.84 02/Jul/2011: £65.28 03/Jul/2011: £54.40 Total Price: £179.52 ---------------------------------------- Rate: One Month Advanced Rate Bed and Breakfast 01/Jul/2011: £69.84 02/Jul/2011: £75.28 03/Jul/2011: £64.40 Total Price: £209.52 ---------------------------------------- Rate: One Month Advanced Rate Dinner, Bed and Breakfast 01/Jul/2011: £94.84 02/Jul/2011: £100.28 03/Jul/2011: £89.40 Total Price: £284.52 ---------------------------------------- Rate: Two Week Advances Rate Room Only 01/Jul/2011: £67.32 02/Jul/2011: £73.44 03/Jul/2011: £61.20 Total Price: £201.96 ---------------------------------------- Rate: Two Week Advances Rate Bed and Breakfast 01/Jul/2011: £77.32 02/Jul/2011: £83.44 03/Jul/2011: £71.20 Total Price: £231.96 ---------------------------------------- Rate: Two Week Advances Rate Dinner, Bed and Breakfast 01/Jul/2011: £102.32 02/Jul/2011: £108.44 03/Jul/2011: £96.20 Total Price: £306.96 ---------------------------------------- Rate: Fully Flexible Rate Room Only 01/Jul/2011: £74.80 02/Jul/2011: £81.60 03/Jul/2011: £68.00 Total Price: £224.40 ---------------------------------------- Rate: Fully Flexible Rate Bed and Breakfast 01/Jul/2011: £84.80 02/Jul/2011: £91.60 03/Jul/2011: £78.00 Total Price: £254.40 ---------------------------------------- Rate: Fully Flexible Rate Dinner, Bed and Breakfast 01/Jul/2011: £109.80 02/Jul/2011: £116.60 03/Jul/2011: £103.00 Total Price: £329.40 ---------------------------------------- ================================================================================ LONLEISQR : London Leicester Square Staying on 01/Jul/2011 for 3 nights Available Rates: Rate: One Month Advanced Rate Room Only 01/Jul/2011: £61.60 02/Jul/2011: £67.20 03/Jul/2011: £56.00 Total Price: £184.80 ---------------------------------------- Rate: One Month Advanced Rate Bed and Breakfast 01/Jul/2011: £71.60 02/Jul/2011: £77.20 03/Jul/2011: £66.00 Total Price: £214.80 ---------------------------------------- Rate: One Month Advanced Rate Dinner, Bed and Breakfast 01/Jul/2011: £96.60 02/Jul/2011: £102.20 03/Jul/2011: £91.00 Total Price: £289.80 ---------------------------------------- Rate: Two Week Advances Rate Room Only 01/Jul/2011: £69.30 02/Jul/2011: £75.60 03/Jul/2011: £63.00 Total Price: £207.90 ---------------------------------------- Rate: Two Week Advances Rate Bed and Breakfast 01/Jul/2011: £79.30 02/Jul/2011: £85.60 03/Jul/2011: £73.00 Total Price: £237.90 ---------------------------------------- Rate: Two Week Advances Rate Dinner, Bed and Breakfast 01/Jul/2011: £104.30 02/Jul/2011: £110.60 03/Jul/2011: £98.00 Total Price: £312.90 ---------------------------------------- Rate: Fully Flexible Rate Room Only 01/Jul/2011: £77.00 02/Jul/2011: £84.00 03/Jul/2011: £70.00 Total Price: £231.00 ---------------------------------------- Rate: Fully Flexible Rate Bed and Breakfast 01/Jul/2011: £87.00 02/Jul/2011: £94.00 03/Jul/2011: £80.00 Total Price: £261.00 ---------------------------------------- Rate: Fully Flexible Rate Dinner, Bed and Breakfast 01/Jul/2011: £112.00 02/Jul/2011: £119.00 03/Jul/2011: £105.00 Total Price: £336.00 ---------------------------------------- ================================================================================ LONHIGHOL : London High Holborn Staying on 01/Jul/2011 for 3 nights Available Rates: Rate: One Month Advanced Rate Room Only 01/Jul/2011: £59.84 02/Jul/2011: £65.28 03/Jul/2011: £54.40 Total Price: £179.52 ---------------------------------------- Rate: One Month Advanced Rate Bed and Breakfast 01/Jul/2011: £69.84 02/Jul/2011: £75.28 03/Jul/2011: £64.40 Total Price: £209.52 ---------------------------------------- Rate: One Month Advanced Rate Dinner, Bed and Breakfast 01/Jul/2011: £94.84 02/Jul/2011: £100.28 03/Jul/2011: £89.40 Total Price: £284.52 ---------------------------------------- Rate: Two Week Advances Rate Room Only 01/Jul/2011: £67.32 02/Jul/2011: £73.44 03/Jul/2011: £61.20 Total Price: £201.96 ---------------------------------------- Rate: Two Week Advances Rate Bed and Breakfast 01/Jul/2011: £77.32 02/Jul/2011: £83.44 03/Jul/2011: £71.20 Total Price: £231.96 ---------------------------------------- Rate: Two Week Advances Rate Dinner, Bed and Breakfast 01/Jul/2011: £102.32 02/Jul/2011: £108.44 03/Jul/2011: £96.20 Total Price: £306.96 ---------------------------------------- Rate: Fully Flexible Rate Room Only 01/Jul/2011: £74.80 02/Jul/2011: £81.60 03/Jul/2011: £68.00 Total Price: £224.40 ---------------------------------------- Rate: Fully Flexible Rate Bed and Breakfast 01/Jul/2011: £84.80 02/Jul/2011: £91.60 03/Jul/2011: £78.00 Total Price: £254.40 ---------------------------------------- Rate: Fully Flexible Rate Dinner, Bed and Breakfast 01/Jul/2011: £109.80 02/Jul/2011: £116.60 03/Jul/2011: £103.00 Total Price: £329.40 ---------------------------------------- ================================================================================ LONKINGSX : London Kings Cross Staying on 01/Jul/2011 for 3 nights Available Rates: Rate: One Month Advanced Rate Room Only 01/Jul/2011: £61.60 02/Jul/2011: £67.20 03/Jul/2011: £56.00 Total Price: £184.80 ---------------------------------------- Rate: One Month Advanced Rate Bed and Breakfast 01/Jul/2011: £71.60 02/Jul/2011: £77.20 03/Jul/2011: £66.00 Total Price: £214.80 ---------------------------------------- Rate: One Month Advanced Rate Dinner, Bed and Breakfast 01/Jul/2011: £96.60 02/Jul/2011: £102.20 03/Jul/2011: £91.00 Total Price: £289.80 ---------------------------------------- Rate: Two Week Advances Rate Room Only 01/Jul/2011: £69.30 02/Jul/2011: £75.60 03/Jul/2011: £63.00 Total Price: £207.90 ---------------------------------------- Rate: Two Week Advances Rate Bed and Breakfast 01/Jul/2011: £79.30 02/Jul/2011: £85.60 03/Jul/2011: £73.00 Total Price: £237.90 ---------------------------------------- Rate: Two Week Advances Rate Dinner, Bed and Breakfast 01/Jul/2011: £104.30 02/Jul/2011: £110.60 03/Jul/2011: £98.00 Total Price: £312.90 ---------------------------------------- Rate: Fully Flexible Rate Room Only 01/Jul/2011: £77.00 02/Jul/2011: £84.00 03/Jul/2011: £70.00 Total Price: £231.00 ---------------------------------------- Rate: Fully Flexible Rate Bed and Breakfast 01/Jul/2011: £87.00 02/Jul/2011: £94.00 03/Jul/2011: £80.00 Total Price: £261.00 ---------------------------------------- Rate: Fully Flexible Rate Dinner, Bed and Breakfast 01/Jul/2011: £112.00 02/Jul/2011: £119.00 03/Jul/2011: £105.00 Total Price: £336.00 ---------------------------------------- ================================================================================ LONEUSTON : London Euston Staying on 01/Jul/2011 for 3 nights Available Rates: Rate: One Month Advanced Rate Room Only 01/Jul/2011: £62.48 02/Jul/2011: £68.16 03/Jul/2011: £56.80 Total Price: £187.44 ---------------------------------------- Rate: One Month Advanced Rate Bed and Breakfast 01/Jul/2011: £72.48 02/Jul/2011: £78.16 03/Jul/2011: £66.80 Total Price: £217.44 ---------------------------------------- Rate: One Month Advanced Rate Dinner, Bed and Breakfast 01/Jul/2011: £97.48 02/Jul/2011: £103.16 03/Jul/2011: £91.80 Total Price: £292.44 ---------------------------------------- Rate: Two Week Advances Rate Room Only 01/Jul/2011: £70.29 02/Jul/2011: £76.68 03/Jul/2011: £63.90 Total Price: £210.87 ---------------------------------------- Rate: Two Week Advances Rate Bed and Breakfast 01/Jul/2011: £80.29 02/Jul/2011: £86.68 03/Jul/2011: £73.90 Total Price: £240.87 ---------------------------------------- Rate: Two Week Advances Rate Dinner, Bed and Breakfast 01/Jul/2011: £105.29 02/Jul/2011: £111.68 03/Jul/2011: £98.90 Total Price: £315.87 ---------------------------------------- Rate: Fully Flexible Rate Room Only 01/Jul/2011: £78.10 02/Jul/2011: £85.20 03/Jul/2011: £71.00 Total Price: £234.30 ---------------------------------------- Rate: Fully Flexible Rate Bed and Breakfast 01/Jul/2011: £88.10 02/Jul/2011: £95.20 03/Jul/2011: £81.00 Total Price: £264.30 ---------------------------------------- Rate: Fully Flexible Rate Dinner, Bed and Breakfast 01/Jul/2011: £113.10 02/Jul/2011: £120.20 03/Jul/2011: £106.00 Total Price: £339.30 ---------------------------------------- ================================================================================ Program finished
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