# geartrain1.mod OBR2-AN-4-0
# AMPL coding: S. Leyffer, January 1999.
#
# Source: Gear Train design problem
# E. Sangren,
# "Nonlinear Integer and Discrete Programming in Mechanical Design
# Optimization", Trans. ASME, J. Mech. Design 112, 223-229, 1990.
#
# Number of variables: 4 (4 integer variables)
# Number of constraints: 0
# Objective nonlinear
# Bound constraints
set I := 1..4;
var x {i in I} >= 12, <= 60, integer;
minimize GearRatio:
( 1.0/6.931 - (x[3]*x[2]) / (x[1]*x[4]) )^2;