The DUALCO parameter is used to set the level of dual computations performed by the solver. Setting DUALCO to 0 will cause LINGO to not compute dual values and ranges. This is the fastest option, but is suitable only if you don’t need this information. In fact, the RANGE command will not execute when DUALCO is 0. When DUALCO is 1, LINGO will compute dual values, but not ranges. When DUALCO is 2, LINGO computes both dual prices and ranges. Setting DUALCO to 3 causes LINGO to compute the dual values on optimizable rows only (i.e., fixed rows are excluded) and forgo range computations. LINGO defaults to a DUALCO value of 1.