Re: [Emc-developers] Building a new C++ kinematics module

[Michael H. <ma...@ma...>]

Am 12.11.2013 um 07:30 schrieb Frank Tkalcevic <fr...@fr...>:

> 
>> ikfast got my attention recently and I looked for someone who could help 
>> me make custom kinematics for 6 axis articulated robot. Can I ask you to 
>> help find the way to do it with ikfast?
> 
> It was your discussion that got me interested in ikfast.
> 
> I don't think it is going to be simple.  I've got a small 4DoF arm.  I
> managed to get the Translate3D iktype working in simulation mode.  Getting
> it to work in realtime mode is probably going to require rewriting the
> generated ikfast C++ module into C as Michael suggested.
> 
> After I got the Translate3D working, I tried TranslationXAxisAngle4D.  This
> is failing, I think because it allocates an array of double[24][24][23]
> (106k) plus another couple of huge arrays defined on the stack.  I get a
> compiler warning...
> 
> warning: the frame size of 117088 bytes is larger than 2560 bytes
> [-Wframe-larger-than=]

it's from src/Makefile:
Makefile:EXTRA_CFLAGS += $(call cc-option,-Wframe-larger-than=2560) $(call cc-option,-Wno-declaration-after-statement)

this limitation comes from the limited kernel stack size and applies to kernel threads only. It does not apply to userland RT threads builds (rt-preempt, xenomai) using this: http://static.mah.priv.at/public/UnifiedBuild.html (even though the warning might be generated when building userland RT modules; this probably should be removed or rather replaced by a sensible limit derived from the specific thread system used).

I dont see an easy way around this limitation short of using statics or some form of dynamic memory allocation for such blobs

-m

> which I think is corrupting the stack.  I don't know where this 2560 limit
> is defined.
> 
> I did manage to get it working by changing the code and making the large
> arrays static, but it's not the right way to do it.
> 
> Frank
> 
> 
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