On Mon, Feb 8, 2010 at 6:13 PM, Noli Sicad
<address@hidden> wrote:
I search the archive regarding this topic -ord
Andrew's reply below but hard to understand.
http://www.mail-archive.com/address@hidden/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
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