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.TH min_qcost_flow 1 "September 1995" "Scilab Group" "Scilab function"
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min_qcost_flow - minimum quadratic cost flow
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[c,phi,flag] = min_qcost_flow(eps,g)
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: row vector of the value of flow on the arcs
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: feasible problem flag (0 or 1)
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\fVmin_qcost_flow\fR computes the minimum quadratic cost flow in the network
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\fVg\fR. It returns the total cost of the flows on the arcs \fVc\fR and
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the row vector of the flows on the arcs \fVphi\fR. \fVeps\fR is the precision
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of the iterative algorithm. If the problem is not feasible (impossible to
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find a compatible flow for instance), \fVflag\fR is equal to 0, otherwise it
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The bounds of the flow are given by the elements \fVedge_min_cap\fR and
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\fVedge_max_cap\fR of the graph list.
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The value of the maximum capacity must be greater than or equal to the
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value of the minimum capacity.
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If the value of \fVedge_min_cap\fR or \fVedge_max_cap\fR is not given (empty
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row vector \fV[]\fR), it is assumed to be equal to 0 on each edge.
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The costs on the edges are given by the elements \fVedge_q_orig\fR and
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\fVedge_q_weight\fR of the graph list. The cost on arc \fVu\fR is given by:
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\fV(1/2)*edge_q_weight[u](phi[u]-edge_q_orig[u])^2\fR
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The costs must be non negative.
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If the value of \fVedge_q_orig\fR or \fVedge_q_weight\fR is not given (empty
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row vector \fV[]\fR), it is assumed to be equal to 0 on each edge.
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This function uses an algorithm due to M. Minoux.
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ta=[1 1 2 2 2 3 4 4 5 6 6 6 7 7 7 8 9 10 12 12 13 13 13 14 15 14 9 11 10 1 8];
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he=[2 6 3 4 5 1 3 5 1 7 10 11 5 8 9 5 8 11 10 11 9 11 15 13 14 4 6 9 1 12 14];
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g=make_graph('foo',1,15,ta,he);
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g('node_x')=[194 191 106 194 296 305 305 418 422 432 552 550 549 416 548];
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g('node_y')=[56 221 316 318 316 143 214 321 217 126 215 80 330 437 439];
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g1=g; ma=arc_number(g1);
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g1('edge_min_cap')=round(5*rand(1,ma));
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g1('edge_max_cap')=round(20*rand(1,ma))+30*ones(1,ma);
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g1('edge_q_orig')=0*ones(1,ma);
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g1('edge_q_weight')=ones(1,ma);
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[c,phi,flag]=min_qcost_flow(0.001,g1);
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if flag==1 then break; end;
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x_message(['The cost is: '+string(c);
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'Showing the flow on the arcs']);
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ii=find(phi<>0); edgecolor=phi; edgecolor(ii)=11*ones(ii);
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g1('edge_color')=edgecolor;
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edgefontsize=8*ones(1,ma); edgefontsize(ii)=18*ones(ii);
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g1('edge_font_size')=edgefontsize;
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g1('edge_label')=string(phi);
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min_lcost_cflow, min_lcost_flow1, min_lcost_flow2