Everything You Know Is Wrong

["Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>]

When I started out in S/W development, I learned some rules, such as, "Integer
math is much faster than floating point," and, "Memory is scarce."

In the 90s, processors began to typically have an FPU, and floating-point math
became as fast as integer, and in some cases, since it could proceed in parallel
with the CPU, faster.

When computers began to commonly have RAM in quantities measured in GB rather
than KB or MB, memory ceased to be scarce, and things that were previously
laughable, such as

type Int_Set is array (Integer) of Boolean;
for Int_Set'Component_Size use Boolean'Size;

became possible (for a 32-bit Integer, Int_Set'Size would be 512 MB). What I
knew is wrong.

Today we learn that memory is much faster than persistent storage. That may soon
be wrong, too. I've been reading about non-volatile memory research, and it
seems that in a few years NV RAM will be available as fast current RAM and as
persistent and durable as current disks.

This will no doubt revolutionize computer architectures and programming
languages. Instead of computers with distinct memory and storage, there will
probably be computers with lots of NV RAM (1-10 TB?) but no disk.

People will no doubt still want a hierarchical naming system for data stored in
that memory, but presumably S/W will map variables onto these "files". So
instead of the current "open, loop over read/modify/write, close" paradigm, we
might have something like

type R is record ...

type L is array (Positive range <>) of R;

F: mapped L with File_Name => "name";

All_Records : for I in F'range loop -- or "of F"

where the bounds of F will be determined from "name". A mechanism will be needed
for collections of heterogenous data as well. F would be equivalent to a
Direct_IO file with in-out mode.

I would think that the Ada 2X project should be thinking about these things, and
wonder what others here think about them.

-- 
Jeff Carter
"He that hath no beard is less than a man."
Much Ado About Nothing
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