Re: [Q]: Distributed System Annex DSA

[bobduff@world.std.com (Robert A Duff)]

In article <3237372C.50E6@joy.ericsson.se>,
Jonas Nygren  <jonas@joy.ericsson.se> wrote:
>Yeah, I noticed my error just before leaving on a buisness trip and posted
>my 'correction', in the taxi to the airport I got an uneasy feeling about
>'Server' versus 'Driver', but since the taxi had no internet service I had 
>no time to check up nor correct any errors a second time - then business class 
>service made me forgetful.

What's the world coming to, when you can't get decent internet service
in a taxi?

>Yes. Almost like magic - perhaps the text should hav emphasized the 
>importance of the 'remote pointer'. But: once told - never forget.

Any sufficiently advanced technogoy is indistinguishable from magic.
Who said that?  ;-)

Anyway, note that my description was just one possible implementation.
The best one, I think.  But another implementation is to make the access
values represented in some special way (maybe, fat pointers, containing
a node number plus an address within node).  It amounts to the same
thing -- the procedure being called doesn't need to know that it's being
called remotely, because some piece of software packages up the data
coming in, and unpackages the data coming out, and so forth.

>I dived into the Gnat DSA code and found in s-rpc.adb that a maximum of
>127 anonymous tasks were created. Though, the stack size of these tasks
>were fixed (~150 kb) and the configuration files (.cfg) did not seem to 
>support a user defined stack size (well, 150 kb may seem enough in most cases
>and also to much in other cases and finally to little in the odd case,
>it would be nice if it was confgurable).

You should keep in mind that the Ada RM envisions the *user* writing the
PCS.  The Ada compiler vendor doesn't (necessarily) provide it.

That doesn't mean that every Ada programmer needs to write his own.
The compiler vendor will usually provide one, and third parties might
provode one.  But keep in mind that you can write your own, or modify
the one you got from gnat dsa.

My point is, you can take that code and use a different max-tasks, and a
different task stack size, or whatever.  It's not exactly the same thing
as taking GNAT and modifying the compiler to recognize a different
language.  With free software, you can modify anything you want.  But
this is different -- a well-defined interace, and you can expect *any*
any compiler to provide this interface.

- Bob