There is an inhomogeneity between AMPL and MathProg in the way sets of
ordered pairs are being iterated over by two (or more) sum{} statements
which are linked by an iterator variable.
Consider the following sample:
---------------------------
set A :={1..5};
set B :={"b1", "b2", "b3", "b4", "b5"};
set D within {A,B} := {(1,"b2"), (1,"b3"), (1,"b5"), (3,"b3")};
var X {D};
minimize z:
sum{a in (1..5)} sum {(a,b) in D} X[1,b];
---------------------------
AMPL generates:
MIN X[1,b2] + 2 X[1,b3] + X[1,b5]
MathProg generates:
MIN 5 X[1,b2] + 5 X[1,b3] + 5 X[1,b5]
Obviously AMPL links the inner and outer sum{} statements by variable 'a'
and MathProg doesn't.
Bug or feature?
Dr. Peter Ingerfeld
MOPS Optimierungssysteme GmbH & Co KG
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