[Coin-lpsolver] help solve a lp problem please
George Cao
george_cao at hotmail.com
Sun Feb 1 11:29:04 EST 2004
Hi everyone,
For the lp gurus in the group, can you guys take a look at this problem
and see if you can provide some pointers?
maximize:
r1* x1a + r2 * x1b + r2*x2 (note: r1, r2 are constants and r2 is
always greater than r1)
Subject to:
x1a + x1b <= d1
x2 <= d2
10 * x1b <= d1
x1a <= c1
x1b + x2 <= c2
x1a, x1b, x2 >=0
This works fine so far. But I need to add a couple more constraints:
if (c1 - d1) >= 0 let x1b = 0
if (c1 - d1) < 0 x1b can be any number >= 0
I can't figure out how to incorporate these constraints into the lp
problem. Adding (c1 - x1a - x1b) >= 1000000 * x1b works when (c1 - x1a
- x1b) >= 0, but will make the whole problem not feasible when (c1 - x1a
- x1b) < 0.
Some help please?
Thanks in advance.
George
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