Re: How to get Ada to ?cross the chasm??

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

"Niklas Holsti" <niklas.holsti@tidorum.invalid> wrote in message 
news:fllcvaF4mg7U1@mid.individual.net...
...
> That makes a point about the smallness of the Turbo Pascal compiler. AIUI 
> the compiler was written in assembly language by a very skilled 
> programmer, and was aimed at fast compilation rather than fast code (any 
> machine code was blazing fast compared to Basic...).

Correct: Turbo Pascal was fast because they found a way to fit it all in 
memory at once (tough on machines that only had 256K or so of memory) and 
because they didn't try to produce good code. Probably 95% of the 
compilation time for Turbo Pascal was disk I/O (something they always left 
out of their compilation speeds -- no compiler could have compiled more than 
a thousand lines or so a second on early MS-DOS because one couldn't read 
the source code any faster than that).

> Perhaps Randy could quote some comparative size numbers for the early 
> versions of Janus/Ada? Though I understand that Janus/Ada required HW 
> memory extenders for the early PCs, just as the early Alsys compilers did 
> (according to the Wheeler essay; again I have no personal experience).

Janus/Ada for PCs ran on bare MS-DOS (originally in 256K of memory, later in 
512K). It could use extended/expanded memory if it was available to expand 
the symboltable; and later versions used a code-swapping mechanism to keep 
the entire thing in memory.

But virtually the entire time (including today), Janus/Ada was primarily 
disk-bound -- the rather extensive I/O took the vast majority of the 
compilation time. The only exception is the optimizer (which can be turned 
off).

I recall that the early PC versions took 2-4 minutes to compile a 
decent-sized Ada package with basic optimization. This was very competitive 
with other compilers for other languages on early PCs and CP/M (we tried a 
number of them in the early days). That is, it wasn't that compiling Ada was 
slow. It was that compiling anything on machines of that era was slow.

                                                    Randy.