[Mono-osx] GDI+ OSX performance

[Alex Shulgin]

LKeene wrote:
> Alex,
> 
> no the code is not being executed within a loop. The pinned array is used as
> a mechanism to allow fast pixel processing while avoiding unsafe code. The
> method works very well. See the article here:
> http://www.howtocode.net/software-development/multimedia/fast-pointerless-image-processing-in-net

Thanks, I will take a look.

> I haven't yet tried profiling. That will be the next step. However, all my
> binaries are VS2008 which I am executing on the Mono runtime. What profiling
> tools are available for use on Mac?

There's Mono profiler (built in into `mono' binary IIRC).  Refer to 
http://www.mono-project.com/Performance_Tips

Haven't tried it on Mac, but I guess it's currently the only tool 
available.  There was some buzz about visual profiler recently--try 
googling for it.

--
Best of luck,
Alex


> Alexander Shulgin wrote:
>> LKeene wrote:
>>> Hi Alex,
>>>
>>> it's in response to an earlier thread I started wherein I was getting
>>> very
>>> poor performance. Someone suggested it was due to Graphics object
>>> allocations being a bottleneck:
>>>
>>> http://www.nabble.com/Horrible-performance-on-Mac%2C-need-advice.-td24507897.html
>>>
>>> Any thoughts on the matter? I'm soon going to tackle this performance
>>> issue
>>> full-force and I'd very much like to get some ideas of where (in general)
>>> to
>>> start.
>> I hope you are not trying to say that the code you presented in that 
>> mail[1] is executed in the tight loop.  Otherwise it's strange to expect 
>> it to perform any good.
>>
>> //...
>> handle = GCHandle.Alloc(Channel1BitmapBytes, GCHandleType.Pinned); // 
>> Pin the array.
>> IntPtr channel1PTR = 
>> Marshal.UnsafeAddrOfPinnedArrayElement(Channel1BitmapBytes, 0);
>> Channel1Bitmap  = new Bitmap(this.CanvasWidth, this.CanvasHeight, 
>> stride, myPixelFormat, channel1PTR);
>>
>> // ...later on (in Paint event handler for example)...
>> Graphics grafix = Graphics.FromImage(Channel1Bitmap);
>>
>>  > "Channel1BitmapBytes" is a declared globally (within the context of
>>  > "this") and, because the array is pinned, I can write to it in
>>  > multi-threaded fashion.
>>
>> I fail to see how pinning the array helps in multi-threaded access.  Do 
>> you use any synchronization primitives?
>>
>> Also, did you try profiling?
>>
>> --
>> Kind regards,
>> Alex
>>
>> [1] http://go-mono.com/forums/#nabble-p24577325
>>
>>> Alexander Shulgin wrote:
>>>> LKeene wrote:
>>>>> Hello all, I'm revisiting an old issue. Has anyone seen (big)
>>>>> performance
>>>>> issues with Mono + OSX regarding the use of:
>>>>>
>>>>> Graphics grafix = Graphics.FromImage(SomeBitmap);  ?
>>>> No.  Why?
>>>>
>>>> --
>>>> Alex