hello everyone,
i have a question about my aimms project:
i have two variables: x(t,k) and y(t,k)
now i want to determine, that
if x(t,k) < y(t,k) then y(t,k) = x(t,k)
i already know that this is not possible with an if-statement.
has anybody an idea?
Thanks in advance.
Seb
Best answer by akumar
One way to approach this is to introduce an auxillary variable z(t,k) and solve for following
Max z(t,k)
s.t
z(t,k) <= x(t,k)
z(t,k) <= y(t,k)
Other way, you can try out is:
Write following constraints (introduce dummy binary variable delta(t,k) and build following relations)
x(t,k) <= y(t,k) + (big-M)*delta(t,k)
x(t,k) >= y(t,k) -(big-M) *(1-delta(t,k))
Write Indicator constraints in AIMMS as
if delta(t,k)=0 then z(t,k) = x(t,k)
if delta(t,k)=1 then z(t,k) = y(t,k)
Best Wishes,
Kumar.
+7What type of variables are x and y? Binary, integer, or continuous?
+7But kan x also be greater than y? That is not completely clear to me from what you write.
yes, that’s right. x can also be greater than y.
so in short i compare two variables and want both to adopt the lower value.
One way to approach this is to introduce an auxillary variable z(t,k) and solve for following
Max z(t,k)
s.t
z(t,k) <= x(t,k)
z(t,k) <= y(t,k)
Other way, you can try out is:
Write following constraints (introduce dummy binary variable delta(t,k) and build following relations)
x(t,k) <= y(t,k) + (big-M)*delta(t,k)
x(t,k) >= y(t,k) -(big-M) *(1-delta(t,k))
Write Indicator constraints in AIMMS as
if delta(t,k)=0 then z(t,k) = x(t,k)
if delta(t,k)=1 then z(t,k) = y(t,k)
Best Wishes,
Kumar.
Hi
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