Re: [SOSlib-devel] wrong AST_FUNCTION_ABS implementation

[Stefan M. <ste...@oe...>]

hi rainer!

you are right. currently the implementaion is wrong.
it should be as it's written in the comment.
f(x)=abs(a(x)) => f' = sig(a)*a'

don't worry about the discontinuity at x=0! :)

cheers, s


Am Freitag 09 Juni 2006 17:46 schrieb Rainer Machne:
> Hi Stefan
>
> I am currently going through the code, implementing the style convention
> and getting familiar with SOSlib again :-)
>
> in differentiateAST we have the lines
>
>      case AST_FUNCTION_ABS:             /** ABS: WRONG */
>        /* f(x)=abs(a(x)) => f' = sig(a)*a'
>  	  WRONG: CAN RESULT IN A DISCONTINUOUS FUNCTION! */
>        ASTNode_setType(fprime, ASTNode_getType(f)); /* WRONG !!! */
>        ASTNode_addChild(fprime, differentiateAST(ASTNode_getChild(f,0),x));
>        break;
>
> So it's actually not doing what it claims in the comment, and also there
> are these uppercase WRONG warnings.
>
> What should we do about that. Should we implement it as written in the
> comment?
>
> Rainer
>
>
>
>
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