Tim Moore

> Sent: 01 April 2008 12:35
> To: FlightGear developers discussions
> Subject: Re: [Flightgear-devel] CVS - Frame Rates under Windows XP
> Hash: SHA1
> Heiko Schulz wrote:
> |
> |> AND, with Linux and the same Graphics Card 7800 GS
> |> 512 MB, i can notice the
> |> same decrease of performance from FG-PLIB  to FG-OSG
> |> ,
> |> I ever had   about 20% less performance   with OSG.
> |>
> |> I am running FG on  AMD ATHLON 3200 (32 bit) with
> |> AGP  mothercard.
> |>
> |> May be OSG is more accurate with modern (recent)
> |> CPU. (i must test it).
> |>
> |>
> |> Cheers
> |>
> |>
> |> --
> | I notice a difference between OSG and Plib too- but
> | this is known!
> | But we can discuss and find out, how to make it
> | faster- time for Tim to answer!
> I suggested that Vivian post his experiences here. I've been 
> working with him for several months on trying to resolve 
> these problems. I'm convinced that his machine is cursed :) I 
> don't develop on Windows and so have run out of ideas other 
> than general suggestions. I'm hoping that more experienced 
> Windows developers will have some ideas for how to proceed.
> One thing seems clear: the OSG version uses more memory than 
> the plib version does. Therefore there is a more memory 
> "pressure;" the entire system needs to deal with this. Memory 
> allocation, especially on Windows, seems to be expensive. ~ 
> Vivian had some improved results today turning off the replay 
> system, which may give us a clue. I think it will only help 
> performance to, in general, optimize the memory usage of FlightGear.

Just an update. Using


Makes FG-OSG as smooth as plib is with


I tried Csaba's MinGW build - frame rates are improved by 20% across the
board, and only 20% below plib (which of course might see further
improvement with a MinGW build.

So I conclude that:
1. There is a problem with replay, 
2. MinGW has about the same performance gap between OSG and plib on XP as
gcc does on Linux.
3. MinGW performance is probably as good as it gets.
4. Either MSVC8 doesn't compile such fast code as MinGW, or there is a
setting wrong somewhere.


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