Here is a description of the von-thunen files that are now available
for downloading by anonymous ftp from the ftp site:
ftp.cs.wisc.edu:math-prog/mcplib/gams
vonthmcp.gms: the GAMSLIB version of the von thunen problem.
pgvon106.gms: the 106 von thunen example as coded by Xiao and modified by
Pang.
pgvon105.gms: pgvon106 with w fixed at 1 (numeraire fixed).
Each of the latter two problems has three starting points:
a) the standard one used for calibration in most general equilibrium
models, that is all values set to 1.
b) starting point generated by Xiao.
c) starting point generated by Xiao but modified to have nonzero
entries throughout.
PEPS: set to 1.E-7; this is a lower bound on the prices of the
problem. Can be set to zero to get lower bounds of 0, but note that the
demands are not well defined in this case.
Computational results for PEPS = 1.E-7:
***************************************
PATH(2.6) SMOOTH
starting pt a) b) c) a) b) c)
PGVON105: 10/10 10/10 10/10 0/10 0/10 0/10
PGVON106: 8/10 6/10 5/10 10/10 10/10 10/10
Notes:
1. PATH(2.6) uses clock control for refactorization, so on poorly
conditioned problems it can sometimes fail, thus we ran each problem
10 times and report the times where a solution was found. SMOOTH is
deterministic, so always finds a solution or always fails.
2. Thanks to Jong-Shi Pang for providing the original definition of
the problems.
3. If you wish to hook up your solver to run as a GAMS/AMPL subsystem
please contact ferris@cs.wisc.edu .