Know any Fortran programmers who need a more interesting job?

[Lee Courtney]

"I still think a 3 tape sort should be a required early assignment (learn
that not everything can fit into memory at once).

TTFN - Guy"

Second.

Lee C.

On Fri, Oct 30, 2015 at 12:15 PM, Guy Sotomayor <ggs at shiresoft.com> wrote:

>
> > On Oct 30, 2015, at 11:35 AM, Paul Koning <paulkoning at comcast.net>
> wrote:
> >
> >
> >> On Oct 30, 2015, at 2:16 PM, Noel Chiappa <jnc at mercury.lcs.mit.edu>
> wrote:
> >>
> >> ...
> >> Apparently nobody had ever told them that a number in memory is... just
> a
> >> number. At which point it became clear that they needed to know a little
> >> more about how a computer actually worked.
> >
> > That reminds me of an exchange I had with a younger colleague who was
> writing a document describing how to do incremental TCP checksum update
> correctly.  He was tripping over the issue of negative zero.  I told him
> the answer simply was to subtract the complement with end around borrow.
> He didn't believe me and ended up proving it by exhaustively testing every
> case.
> >
> >
> My favorite of this class of issues, was when I was working at a startup
> doing an embedded product with Linux as the OS.  We all had Linux machines
> for building/testing.  I was responsible for the Linux kernel at the
> company.  I had someone come up to me and said “the VM system is broken…my
> program works fine on my desktop but I keep getting page faults on the
> embedded platform”.  The conversation was something like this:
> Me:  So, what’s the program doing memory wise?
> Him: I allocate an array of structures and I read them off of disk into
> the array.
> Me: How big are the structures?
> Him: About 4K
> Me: How many are you allocating?
> Him: 100,000
> Me: Rolls eyes.  That’s 4GB.  We don’t have 4GB on the embedded platform.
> You don’t even have that on your workstation.
> Him: But it works there and not on the embedded platform.
> Me: We don’t have paging turned on in the embedded platform.
> Him: Can’t we turn it on?  It makes my code so simple!
> Me: No!  Go allocate a *reasonable* sized array (say 100) and shuffle in
> from the disk when the data you need isn’t there.  You walk the data
> structure mostly sequentially anyway, so there’s no reason to have the
> entire file in memory.
>
> I still think a 3 tape sort should be a required early assignment (learn
> that not everything can fit into memory at once).
>
> TTFN - Guy
>
>


-- 
Lee Courtney
+1-650-704-3934 cell