Re: Counting number of non zeros ?

[Paul]

If the array is a parameter array, rather than a variable array, then yes. If it is a variable array, I think you'll need a binary variable array of equal dimension and a whole bunch of constraints.

Paul

[victor.z...@gmail.com]

Just want to add that there is a count operator that can be used for this purpose both with parameters and variables. The count operator for variables is only supported by the ilogcp solver currently, but there is no such limitation for parameters. See http://www.ampl.com/NEW/LOGIC/index.html#cardop for details.

Here's an example:

set S = 1..10;

var x{S} integer, >= 0;

minimize o: sum{s in S} x[s];

s.t. c: count{s in S} (x[s] != 0) >= 3;

option solver ilogcp;

solve;

display x;

x [*] :=

 1  1

 2  0

 3  0

 4  0

 5  1

 6  1

 7  0

 8  0

 9  0

10  0

;

Victor

On Wed, Oct 31, 2012 at 1:56 PM, Paul <paru...@gmail.com> wrote:

If the array is a parameter array, rather than a variable array, then yes. If it is a variable array, I think you'll need a binary variable array of equal dimension and a whole bunch of constraints.

Paul

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