(j3.2006) DO CONCURRENT question

[Robert Corbett]

On 11/21/12 12:53, Bill Long wrote:
>
> On 11/21/12 1:13 PM, Lionel, Steve wrote:
>> I am puzzled by some wording in the standard regarding DO CONCURRENT and
>> hope one or more of you can shed some light on it.
>>
>> 8.1.6.7, page 178, lines 5-7 say:
>>
>> 5 A variable that is referenced in an iteration shall either be
>> previously defined during that iteration, or
>>
>> 6 shall not be defined or become undefined during any other iteration. A
>> variable that is defined or becomes
>>
>> 7 undefined by more than one iteration becomes undefined when the loop
>> terminates.
>>
>> It then goes on to show in note 8.11:
>>
>> A variable that is effectively local to each iteration of a DO
>> CONCURRENT construct can be declared in
>>
>> a BLOCK construct within it. For example:
>>
>> DO CONCURRENT (I = 1:N)
>>
>> BLOCK
>>
>> REAL :: T
>>
>> T = A(I) + B(I)
>>
>> C(I) = T + SQRT(T)
>>
>> END BLOCK
>>
>> END DO
>>
>> If the BLOCK were removed, so that T was a procedure scope variable, why
>> wouldn?t ?previously defined during that iteration? be sufficient to
>> effectively make T local to each iteration, negating the need here for
>> BLOCK?  Or am I misreading this?
> No. You are right that the BLOCK is not technically needed here.  What
> it does is remove any issue concerning T "becomes undefined when the
> loop terminates" since (this) T does not even exist at the end of the
> loop.
>
> Cheers,
> Bill
>

What about the case of module variables, variables in common,
and variables from an enclosing scoping unit?  They will not
be easy to "localize."

Bob Corbett