I search the archive regarding this topic -ord Andrew's reply below but hard to understand.
http://www.mail-archive.com/[email protected]/msg01281.html Anyway, I tried to reformulate based on how I understand it. Revised model below. It is still not working. Noli ~~~~~~~~~~ # mrp.mod # AMPL: Data for mrp formulation set PP; # ordered; # Set of SKU Numbers set TT; # ordered; # Set of Time Buckets param ord1{i in PP, s in TT}; param ord2{i in PP, t in TT}; param P integer := card(PP); # Number of SKUs param T integer := card(TT); # Number of Time Buckets param M >= 0; # Large Number param LT {PP} integer; # Lead Time param R {PP,PP} integer; # number of i to make one j param D {PP, TT} integer; # External Demand for an item in a period param I {PP} integer; # Beginning Inventory param LS {PP} integer; # Lot Size var d {PP, TT} binary; # production indicator var x {PP, TT} >=0; # number of SKUs to produce # ----------------------------------------------------------------- minimize objective: sum {i in PP, t in TT} (T-ord2(t)+1) * x[i,t]; # ----------------------------------------------------------------- subject to MaterialRequirement {i in PP, t in TT}: (sum {s in TT: ord1(s) <= ord2(t)-LT[i] } x[i,s] ) + I[i] - sum {s in TT: ord1(s)<=ord2(t)} (D[i,s] + sum {j in PP} R[i,j]* x[j,s]) >= 0; subject to LotSize {i in PP, t in TT}: x[i,t] - d[i,t]*LS[i] >= 0; subject to ProductionIndicator {i in PP, t in TT}: d[i,t] - x[i,t]/M >=0; Error, GLPSOL: GLPK LP/MIP Solver, v4.42 Parameter(s) specified in the command line: --cover --clique --gomory --mir -m mrp_c3.mod Reading model section from mrp_c3.mod... mrp_c3.mod:28: function ord2 unknown Context: minimize objective : sum { i in PP , t in TT } ( T - ord2 ( MathProg model processing error >Exit code: 1 Time: 0.206 _______________________________________________ Help-glpk mailing list [email protected] http://lists.gnu.org/mailman/listinfo/help-glpk
