Multi-threading access to MapPoint?

Question

Good afternoon,

As I said earlier in another post, I have to calculate some 8,000,000 shortest- time/path distances between some points in the map, the coordinates of which are know. The problem is that, while straight-line distances were easy (and quick) to calculate, someone told me that a single-threaded application can have problems calculating this number of distances using MapPoint. The question is that I know nothing about multi-threading... I am currently working on a i7 - 720QM environment, so I would like to use all the 4 cores to make these calculations... Is there any easy way of doing this in C# or C++?

Thank you very much.

Answer 1

If you are totally new to the Multithreading than my advice start with BackGroundWorker component as a starting point and gradually switch to more garnular threading concepts.

and if you are using ..net 4.0 than Task Parallel Library gives you easy way to start with.

See Links Below

TPL

BackGroundWorker

Answer 2

That might have been me who said it would take a long time. MapPoint's COM API is single threaded. The way to get it to compute multiple routes in parallel is to start multiple MapPoint's, each on its own thread.

So for your quad core, you will start 2-3 threads. Each thread starts its own MapPoint, and then uses it for routing. You will NOT have one MapPoint per core. As well OS overhead and your I/O overhead, if you watch a single MapPoint compute a route, you will find that later versions are partially internally multi-threaded and can take about 1.5 cores if they are available.

There are also a lot of gotchas to watch out for. MapPoint's own garbage collection is not optimized for batch route calculation. The easiest workaround for this is to simply restart each MapPoint application at periodic intervals (at least once a day but probably more frequently).

Also, some operations (File Open seems to be the main one) cannot be called by multiple MapPoints at once. Probably because they are trying to open the same file, but I have not investigated further. You will need to implement your own locking mechanism to avoid this.

Saurabh's advice for .NET 4 sounds good: I have yet to use .NET 4's multi-threading in anger - my MapPoint/.NET threading experience is with .NET 2.

I don't know what your app is, but did you know that I sell a product that uses multi-processor MapPoint for batch route distance/time calculation... :-)