[Help-glpk] [Fwd: GMPL Piping Feature Request (for SolverStudio integration)]

[Andrew Makhorin]

-------- Forwarded Message --------
From: Andrew Mason <address@hidden>
To: address@hidden, address@hidden
Subject: GMPL Piping Feature Request (for SolverStudio integration)
Date: Mon, 23 Jul 2012 14:38:24 +1200

Andrew,

As an extension to my work with OpenSolver, I have been developing
SolverStudio, a free Excel add-in that makes AMPL and GMPL available for
building models inside Excel. (See http://solverstudio.org and
http://opensolver.org for more info). I have really enjoyed working with
GMPL to add it as an option in SolverStudio; it's a great system you
have created.

One issue I have come up against is the lack of piping in GMPL's
"display" command. In AMPL, I use the following to write the AMPL
solution back to the spreadsheet (via a file called 'Sheet'):

# Write the solution to the sheet
display Amount > Sheet;

In GMPL, I cannot use ">" with display, but I can with print. This means
the GMPL commands look something like the following (for a slightly
different example):

# Write the solution to the sheet (copying AMPL's display format)
# Each item is quoted to ensure spaces in items work correctly
printf "flow :=\n" >> "Sheet";
printf {i in Warehouses, j in Bars}: "'%s' '%s' '%s'\n",  i, j,
flow[i,j] >> "Sheet";
printf ";\n" >> "Sheet";

This makes it difficult for users (including my students) to easily
switch from AMPL to GMPL. I was wondering if, when you were next making
changes to the GMPL code, you could add piping to GMPL's display
command. It would certainly help us, and, I'm sure, other SolverStudio
and GMPL users.

Thanks,

Andrew

-- 

Dr Andrew J Mason
Dept of Engineering Science
University of Auckland
New Zealand
+64 9 3737599 x87909
www.esc.auckland.ac.nz/Mason
address@hidden

www.OpenSolver.org: An open-source Solver-compatible LP/IP optimizer for Excel