[daip] Re: IBM compiler

[Eric Greisen]

Lincoln writes:

 > Shoshana told me (I just remembered) that
 > the Absoft compiler supports 64 bit and IBM
 > only 32 bit.  That sounded great  - and scary.
 > If we buy absoft, we would want to make comparisons
 > of Absoft and gnu computing results. Would you
 > recommend a particular set of exercises?
 > 

AIPS has no use for 64-bit so some care needs to be taken.  I suspect
that one gets the 32-bit data okay, but 64-bit addresses.

I then worry that the 64-bit might do what one crazy system in Italy
did - give dynamic memory at one end of the address range and regular
program memory at the other.  In that case, the way we currently do
dynamic memory breaks - we assume that a 32-bit integer subscript may
be used to represent the offset in words.  I do have code I was
looking at that would fix this except that I took advantage of the way
the pseudo-AP is constructed (one array with many offsets in it) to
allow for a dynamic memory pseudo-AP in FRING.  To make all pseudo-AP
subscripts be LONGINT (and all subscripts in the Q routines) would be
a very big job.  I would have to drop the dynamic memory in FRING at
least for 64-bit address space machines, even those that do not do the
crazy malloc's.

Thus it is a bit of a gamble.  Use Y2K large or DDT large for the
initial tests.

Eric Greisen