Re: GNAT and Tasklets

["Randy Brukardt" <randy@rrsoftware.com>]

"Brad Moore" <brad.moore@shaw.ca> wrote in message 
news:Wsilw.1234991$1s.181390@fx05.iad...
> On 14-12-19 06:05 PM, Randy Brukardt wrote:
...
>>> I think that the block should have explicit parameters, e.g. Total must 
>>> be
>>> an in-out parameter of the block. The syntax should be similar to the
>>> selective accept. Each arm must also have parameters, and only those and
>>> of
>>> the block must be visible within an arm. E.g. A, B must be parameters.
>>> Nothing else should be visible.
>>
>> Interesting. This does sound like a better approach to me. (The whole
>> reduction object idea seems to me to be the worst part of the parallel
>> proposals -- something needs to be available, but that doesn't seem to be
>> the way to do it.)
>>
>> OTOH, the syntax to specify such parameters doesn't seem natural. We 
>> surely
>> don't want to force a parallel block or loop to be the only contents of a
>> subprogram.
...
> As for reduction. We haven't yet discussed reduction for parallel blocks. 
> It's not clear that we even need that, because in a parallel block, it 
> seems easy enough to declare separate variables, and then write the 
> reduction yourself.

I was more reacting to the method of specfying reduction for parallel 
statements (I hadn't realized that it was only allowed for loops, that seems 
inconsistent to me, even if it is mostly necessary for the loop construct).

The problem I have is that it is really hard to wrap one's mind around the 
idea of reduction objects and reduction operations and especially reduction 
identity value. I'd like to it be more able to be obvious from the code 
specified. (I.e., if Total is being added in the loop, then clearly it will 
be reduced that way.) But I'm quite willing to say I don't know how to do 
that (yet), thus "more thought needed". Clearly the reduction objects have 
to be identified to the compiler; it's unclear to me that more is needed. 
After all, how the reduction is done is clearly in the sequential code, 
can't the compiler extract that for parallel reduction?

                                              Randy.