# Gurobi solver in matlab

 0 I want to use Gurobi solver in Matlab, but I don't know how to calculate the required matrices (qrow and qcol). For your reference I am copying the example provided in documentation. 0.5 x^2 - xy + y^2 - 2x - 6y subject to x + y <= 2 -x + 2y <= 2 2x + y <= 3 x >= 0, y >= 0 c = [-2 -6]; objective linear term objtype = 1; minimization A = sparse([1 1; -1 2; 2 1]); % constraint coefficients b = [2; 2; 3]; % constraint right-hand side lb = []; [ ] means 0 lower bound ub = []; [ ] means inf upper bound contypes = '\$<< vtypes = [ ]; [ ] means all variables are continuous QP.qrow = int32([0 0 1]); indices of x, x, y as in (0.5 x^2 - xy + y^2); use int64 if sizeof(int) is 8 for you system QP.qcol = int32([0 1 1]); indices of x, y, y as in (0.5 x^2 - xy + y^2); use int64 if sizeof(int) is 8 for you system QP.qval = [0.5 -1 1]; coefficients of (0.5 x^2 - xy + y^2) Does it mean that if I have 4 decision varaibles than i should use 0,1,2,3 as indices for my decision variables x_1, x_2, x_3, x_4.? Thanks Note: I tried to use mathurl.com but I don't get how to write in proper format show that it will appear as latex text. Sorry for the notation. asked 11 Mar '11, 23:35 Shailesh 1●1●1 accept rate: 0%

 2 I'm not sure this is the right forum to ask questions about usage of a particular piece of software i.e. Gurobi; try this mailing list instead: http://groups.google.com/group/gurobi That said, it seems to me that qrow and qcol are interchangeable. The quadratic expression is obtained through a element-wise multiplication of qrow, qcol and qval. For instance, suppose we have the following expression (where the variables are x0, x1, x2 and x3): 2*x0^2 + 0.2*x0*x3 + 0.1*x0*x2 + x2^2 + 3x1*x3 + 5*x3^2  From the instructions given, I would write the coefficients in qval: qval = [ 2 0.2 0.1 1 3 5 ]  And qrow, qcol would simply be: qrow = [ 0 0 0 2 1 3 ] qcol = [ 0 3 2 2 3 3 ]  If I would assume then that the quadratic part of the objective is then reconstructed as follows: Quads = sum(qval .* x(qrow) .* x(qcol));  where x is some vector with 0...n indexing (n being the number of terms minus 1). answered 12 Mar '11, 04:10 Gilead ♦ 2.3k●5●14 accept rate: 15% Nothing wrong with questions on particular software, though I agree that a gurobi specific group might work better. (12 Mar '11, 09:09) Michael Trick ♦♦ Thank you very much for the detailed explanation. (12 Mar '11, 20:39) Shailesh
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