RE: [pooma-dev] AltView* classes

[James Crotinger]

Hi all,

Jeffrey's email shook a few more things loose. :)

Yes, more classes means more parse time, but the issue was link time. The Blanca folk did explicit instantiation of as much stuff as they could. My recollection was that without explicit instantiation, there was a link-time compile for every view in every file that took a view, or something like that. There was a problem doing implicit instantiation of the views themselves, though I don't remember what the issue was. The solution was to move the enum into the AltView class and explicitly instantiate all of these. With this addition, the linker always found the sv variable and no additional link-time compile was needed.

This is obviously coming from some pretty rusty neurons, but I believe this is the crux of the issue. For large codes, POOMA is a pig at link/compile time (depending on the instantiation model) and there were various possibly non-obvious factorings made along the way in order to try to keep this under control.

        Jim

------------------------------------------------------------------------
James A. Crotinger                           email:     address@hidden
NumeriX, LLC                                 phone:  (505) 424-4477 x104
2960 Rodeo Park Dr. W.
Santa Fe, NM 87505
 

> -----Original Message-----
> From: Richard Guenther [mailto:address@hidden]
> Sent: Tuesday, March 02, 2004 9:54 AM
> To: Jeffrey D. Oldham
> Cc: James Crotinger; 'address@hidden'
> Subject: Re: [pooma-dev] AltView* classes
>
> Jeffrey D. Oldham wrote:
> >
> > James Crotinger wrote:
> >
> >> Hi Richard,
> >>
> >> This tickled a neuron the other day, but I couldn't recall the details.
> >>
> >> The AltView classes were put in to reduce link times and sizes for
> >> large codes. The classes that have enums end up having a link-time
> >> cost, both in space and time. I believe this refactoring was done to
> >> reduce the cardinality of classes having the "sv" enum. My
> >> recollection is that this, and other similar "optimizations", had a
> >> pretty substantial impact on link-time for Blanca. Unless these are
> >> hurting something else, I would tend to leave them in.
>
> It seems they are only used for return type creation which hinted me
> that it may have beed a compiler bug workaround (so does the CVS
> histroy).  As an optimization this looks worthless at it just adds
> classes to parse. No?
>
>
> > The POOMA CVS repository history goes back to at least 1998 March.  For
> > example, see the log for src/Array/Array.h.  This log gives an entry for
> > AltView0 and AltView1Implementation:
> >
> > revision 1.141
> > date: 2001/05/25 17:42:48;  author: oldham;  state: Exp;  lines: +47 -6
> > branches:  1.141.4;
> > 2001-05-25  Jeffrey D. Oldham <address@hidden>
> >     * Array/Array.h (View0): Modify initial comment to indicate
> >     changes should also be made to AltView0.
> >     (AltView0): New class to avoid explicit instantiation problems.
>
> The same comment is above the classes in the source, but it's not very
> helpful in trying to figure out what these problems are/were.
>
> It's in my tree now, so I won't forget about it at least until the next
> treediff to CVS.
>
> Richard.