(!********************************************************************* Mosel NL examples ================= file airport.mos ```````````````` Locate N airports each within a specified distance of a city centre, and minimise the sum of square of the distances between all the airports. QCQP problem. Based on AMPL model airport.mod by Hande Y. Benson Source: http://www.orfe.princeton.edu/~rvdb/ampl/nlmodels/cute/ Reference: Rodrigo de Barros Nabholz & Maria Aparecida Diniz Ehrhardt November 1994, DMA - IMECC- UNICAMP. (c) 2008 Fair Issac Corporation author: S. Heipcke, May 2008, rev. Mar. 2013 *********************************************************************!) model "airport (QPQC)" uses "mmxprs", "mmnl" declarations RN: range ! Set of airports R: array(RN) of real ! Square of max. distance to given location CX,CY: array(RN) of real ! Target location for each point x,y: array(RN) of mpvar ! x-/y- coordinates LimDist: array(RN) of nlctr end-declarations initialisations from "airport.dat" CY CX R end-initialisations ! Set bounds on variables forall(i in RN) do -10<=x(i); x(i)<=10 -10<=y(i); y(i)<=10 end-do ! Objective: minimise the total squared distance between all points TotDist:= sum(i,j in RN | i<j) ((x(i)-x(j))^2+(y(i)-y(j))^2) ! Constraints: all points within given distance of their target location forall(i in RN) LimDist(i):= (x(i)-CX(i))^2+(y(i)-CY(i))^2 <= R(i) (! For exporting the matrix file setparam("XPRS_loadnames", true) loadprob(TotDist) writeprob("airport.mat","l") !) setparam("XPRS_verbose", true); minimise(TotDist); writeln("Solution: ", getobjval); forall(i in RN) writeln(i, ": ", getsol(x(i)), ", ", getsol(y(i))) end-model