Thank you for your answers. It is as I thought. I tested performance of 2 VMs on one single core host computer, but as Stealth said, there has been no increase in speed. I tried to parallely compute the multiplication of two huge matrices, but the time spent on computation was just the same as for the computation on one computer. I tried it with several sizes of matrices, but with there was no improvement even in the big dimensions (where you can assume, that the communication overhead is irrelevant in comparison to the computation time).
Ondrej. Mikkel L. Ellertson wrote: > Stealth wrote: > >> On Friday 12 December 2008 09:06:30 am Ondrej Sluciak wrote: >> >>> I have one very stupid question, but I want to be sure that I am >>> right. If you have 2 interconnected virtual machines running and >>> let them compute some problem in parallel (using message passing >>> interface - MPI), is it really a parallel computation? I mean, >>> when the host machine has only one core and both VMs use the same >>> memory and resources (though separated), can you talk about >>> parallel computation? >>> I'm asking because I did some tests with with such a setup, but I >>> have noticed no improvement in speed, comparing to computation on >>> one VM. Does anyone have some experience with it? Thanks. >>> >> If you mean are you getting quicker results because you are using >> multiple machines? The answer would be, no, because you are using >> one machine. You are simply sharing the one machine's resources >> multiple applications. The VMs are just a process running inside an >> application. Each VM thinks it is a separate machine and the host >> machine just simply sees an application demanding resources. >> >> > If anything, I would expect slower results using 2 virtual machines > because of the added overhead of the second virtual machine. > > I am not sure even having more then one processor or core would > help, because I suspect the VirtualBox is not designed for > multiprocessors or cores. One way to find out would be to open more > then one vm and watch the cpu load. I do not have a second vm set up > right now to test it. I do know that running with one vm, I only use > one core. This is handy because it automatically limits VB's cpu usage. > > Mikkel > -- Dipl.-Ing. Ondrej Sluciak Room CG-04-06 Vienna University of Technology, Austria Institute of Communications and Radio-Frequency Engineering Gusshausstrasse 25-29/389 http://www.nt.tuwien.ac.at _______________________________________________ vbox-users mailing list [email protected] http://vbox.innotek.de/mailman/listinfo/vbox-users
