SAF, XLSX, TCL, IRIX
====================

The SAF  (Static Analysis Format)  is a  modern thing created  by civil
engineers. The idea is  simple: one need a way how  to create an usable
computational model from complex 3D models of buildings.

For  analysis  of  safety  one usually  does  simplified  computational
analysis on much  simpler model: 3D stuff  is reduced to 1D  and 2D (if
really  necessary) elements  which are  used to  computes stresses  and
deformations and to assess them.

Such conversion  can be done in  many ways but relatively  recently the
SAF  format  have became  popular.  It's  a  simple text  format  which
described  the  world  of  1D  and  2D  members  with  their  materials
definitions and more. Sound very easy and optimistic, right?

Well, civil engineers are involved so expects some problems.

Here they are: the texts are included  in many sheets of and Excel file
in XLSX format. Of course, such thing can  be done in CSV or in a plain
text filed but not here. Civil engineers use spreadsheets (the MS Excel
usually) so  they decided to  use this  format to represent  plain text
information!

I have been slowly developing my program code for static analysis of 2D
frame  structures [1].  I'm  doing  it for  ages  (started about  2005,
reviwed is in 2020 during the COVID,  then have reviwed it once more in
early 2026 mostly as an exercise in AI usage).

My programs have to  run on the IRIX (and on the  Linux, of course) and
on the OS x  10.4-10.5, if possible. I often use  Tcl/Tk because t runs
on many platforms.  This code uses the Tcl/Tk 8.0  (or better) and runs
(or rather  walks as the interpreted  language is rather slow  on older
machines...) almost every where (from IRIX 5.3 to the Debian Unstable).

So my  rules for  development are:  Tcl/Tk 8.0,  no UTF-8,  no external
libraries (just  default ones) and the  C extensions in ANSI89  C only.
Pretty hard  limitations you say.  I don't think  so but in  some cases
they make troubles.

One day I have got a crazy idea: I should support SAF I/O (both reading
and writing). This is not easy as  the SAF is basically a 3D format and
my program only  work in 2D. But  it was doable: now I  have a selector
which allows me to select a slice of the 3D model.

But, it's XLSX...  So, unzip and a good portion  of regular expressions
(and a big  portion of help from AI) was  needed. Surprisingly, it have
been  working on  (at  least some)  real  files. I  have  spent a  five
evenings to make this working. On a Linux, of course.

So I got a  crazy idea: I should try if it works  on the IRIX. My Linux
machine (the  MNT Pocket  Reform) has  the modern ARM  CPU so  the code
runs  relatively fast  (don't forget  that  the Tcl  is an  interpreted
language!). But I  was curious how fast  it will be on  my IRIX machine
(the SGI O2 with a 250MHz CPU).

So I  transferred my code  to the O2,  then transferred the  XLSX file,
too. You know, there is NO WAY to  open XLSX on the IRIX. So... I tried
my  program. To  my  great surprise,  it worked!  It  wasn't too  slow,
actually.  It opened  the XLSX,  plotted a  simplified model  o the  3D
structure  on the  canvas, I  selected  my slice  and ...  after a  few
seconds the model was ready!

I used the Tcl.Tk  8.0 as every newer version is a  bit slower. The 8.4
(which is  also available mor my  SGI O2) would noticeably  slower (for
everything).


What  all this  meant? It  means that  I upgraded  usability of  my old
machine  to a  level I  never  expected. I  can open  modern files  and
analyse actual civil engineering structures  (I do have a more powerful
FEA code  which does 3D and  some kinds of non-linearity  but it's more
for research and experimenting than for practical use).
Cool stuff, actually!

Written on the SGI O2.


References:

[1] http://jirka.sdf.org/fem1.tgz