[ExI] portability of spreadsheet models, was RE: ai class at stanford

[spike]

-----Original Message-----
From: extropy-chat-bounces at lists.extropy.org
[mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of Adrian Tymes
Sent: Tuesday, August 23, 2011 5:57 PM
To: ExI chat list
Subject: Re: [ExI] ai class at stanford

On Tue, Aug 23, 2011 at 5:27 PM, spike <spike66 at att.net> wrote:
...
>> example would be an extremely sophisticated atmosphere model, which has
evolved over the years, and takes into account F10.7, geomagnetic 
>> index, latitude, longitude, altitude, time of day, temperature, pressure,
a bunch of other minor factors, and it works really well, but the catch is,
it's a spreadsheet...


>...WARNING!  WARNING!

>...You are attempting to invoke code reuse, of something that was never
designed to be reusable...

It has been reused many times, but in a limited sense.  I have used it to
estimate ascent trajectories of rockets going up through the atmosphere.
Agreed it couldn't be used for predicting hurricane paths.  An example is
when you launch from a particular site, you can enter the local parameters,
then shortly after launch, as you climb you head south, assuming you are
going out of Vandenberg.  Since your latitude is changing, the atmospheric
column is changing as well.  So you can calculate a few hundred milliseconds
ascent, recalculate your latitude, hand that back to the model, have it
recalculate the air column, then do a few hundred more milliseconds, rinse
and repeat.

It is possible that I am working hard to use spreadsheets for this kind of
application, since I know how to do it in a spreadsheet, but not very easily
in Fortran.  Fortran!  See there, I told you I am an old guy.  But I will
give you an insider secret.  Many years ago I was given Lockheed's
atmospheric model in return for entering a whole bunch of data into a
spreadsheet.  Our model was in the form of reams of Fortran code, so I
reverse engineered it into Excel, and put together a product that was one
hell of a lot easier to use for the iterative kinds of calculations I
described above.

spike