(j3.2006) (SC22WG5.4080) [ukfortran] Some minor points on the Draft Final CD

[N.M. Maclaren]

On Sep 9 2009, Aleksandar Donev wrote:
>
>You are right that 6.6 does not cover declarations, but I am not sure 
>what you want the Note concerning declarations to say? It has nothing 
>to do with the number of images---it merely sets the lower and upper 
>cobounds, which is independent of the number of images. Please suggest 
>specific wording so we know what you are asking for.

Yup.  I have drafted some, and will repost in due course.  All it does
is to say what you have said - in different words!

>You are talking about ALL STOP. This is certainly a necessary 
>functionality. How well it is implemented, i.e., what actually happens 
>when it is executed, seems (almost?) entirely processor dependent to me 
>and I do not see how we are burdening or requiring anyone to do too 
>much.

The problem is that paragraph 4 explicitly says that the image that
initiates termination completes termination, even for ALL STOP.  It might
be better to drop that, instead.

>Can someone explain to me how a program can detect the difference 
>between these and how it can tell anything about what happens after ALL 
>STOP is executed. All execution stops and the program cannot tell 
>anything about synchronization etc.

Outstanding data transfers are completed, even those to data on other
images (which I think is allowed).  That's visible.

>The synchronization is there to ensure that shared data does not 
>disappear until all images are done accessing it. In the case of error 
>termination, it does not matter----no more accessing, no more nothing, 
>execution ends. What is left to the OS (a whole lot of hanging 
>processes, a clean slate, a memory leak, or sheer peace and quiet) 
>seems entirely unspecified (and unspecifiable) to me.

I agree, but that's not what the words say. I agree that the 
synchronisation is essential for ordinary STOP, but it is the ALL STOP case 
that concerns me. Again, I am thinking as an implementor, and as a support 
person faced with a case where the user claims that it should work and the 
vendor says that it needn't.

It's not a major point, but is a problem.

Regards,
Nick Maclaren.