[Carpet] type-cast warnings

[Steve White]

This is impressive.

I just sent Erik an e-mail saying I had fixed all these things.

However, I picked out the line 4 above the one Bela mentions as being
particularly scary:

	myinval += (static_cast<const T*>(inarrays.at(tl))[index]
                        * tfacs.at(tl));

It isn't clear to me what "mycnt" is supposed to be doing,...



On 17.10.06, Bela Szilagyi wrote:
> While compiling Carpet on  our AEI cluster "lagavulin" I got the following 
> warnings:
> 
> /home/szilagyi/Cactus/configs/lharm/build/CarpetReduce/reduce.cc(459): warning 
> #                           810: conversion from "double" to 
> "CarpetReduce::typeconv<int>::goodtype={int}"                           m ay 
> lose significant bits
>           mycnt += w;
>                 ^
>           detected during instantiation of "void 
> CarpetReduce::reduce<T,OP>(cons                           t int *, const int 
> *, const int *, const std::vector<const void *, std::allocat                          
> o r<const void *>> &, const std::vector<double, std::allocator<double>> &, 
> void                           *,  void *, const double *, double) [with 
> T=CarpetReduce::typeconv<int>::goodtyp                          e={ int}, 
> OP=CarpetReduce::minimum::op<CarpetReduce::typeconv<int>::goodtype={in                          
> t}>] "
> 
> 
> What is worrisome is that the resulting value of (mycnt) could depend "w" 
> being a roundoff quantity above or below a certain integer.  In case one runs 
> the application across a non-homogeneus architecture cluster, it is very 
> likely that on certain nodes mycnt will have values different from other 
> nodes.
> 
> It is possible that code before this assignment cleans up the value of "w" so 
> that the result is architecture independent.  But I was not able to confirm 
> this.
> 
> The question is then -- should one worry about these kinds of warnings in 
> Carpet(Regrid) ? 
> 
> -- 
> Bela Szilagyi
> 
> Max-Planck-Institut für Gravitationsphysik
> Albert-Einstein-Institut
> Tel: +49 331 567 7632
> Fax: +49 331 567 7649
> 
> _______________________________________________
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> 

-- 
Steve White : Programmer
Max-Planck-Institut für Gravitationsphysik      Albert-Einstein-Institut
Am Mühlenberg 1, D-14476 Golm, Germany                  +49-331-567-7625