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gams:mcp_pair_..._has_empty_equation_but_associated_variable_is_not_fixed

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 gams:mcp_pair_..._has_empty_equation_but_associated_variable_is_not_fixed [2008/01/10 10:41]Franz Nelissen created gams:mcp_pair_..._has_empty_equation_but_associated_variable_is_not_fixed [2020/05/26 13:06]Lutz Westermann model format 2020/05/26 13:06 Lutz Westermann model format2008/01/10 10:41 Franz Nelissen 2008/01/10 10:41 Franz Nelissen created Next revision Previous revision 2020/05/26 13:06 Lutz Westermann model format2008/01/10 10:41 Franz Nelissen 2008/01/10 10:41 Franz Nelissen created Line 5: Line 5: The message indicates that one of the equations is empty -- essentially,​ you have too many variables to be determined uniquely from the given equations. The message indicates that one of the equations is empty -- essentially,​ you have too many variables to be determined uniquely from the given equations. - The model below will give (correctly) the same error : + The model below will give (correctly) the same error: - + <​code>​ - set i /i1,i2/; + Set i /i1,i2/; - alias (i,ii); + Alias (i,ii); - variables ​x(i); + Variables ​x(i); - equations ​e(i); + Equations ​e(i); e(i).. sum(ii\$(ord(ii)=-1),​ x(ii)) =e= 0; e(i).. sum(ii\$(ord(ii)=-1),​ x(ii)) =e= 0; - model m /e.x/; + Model m /e.x/; solve m using mcp; solve m using mcp; + ​ The equation above is a  "​degenerate"​ case in the sense that the lhs vanishes. In that case the matching variable must be fixed (''​x.fx(i)=0;''​). ​ The equation above is a  "​degenerate"​ case in the sense that the lhs vanishes. In that case the matching variable must be fixed (''​x.fx(i)=0;''​). ​ Most likely however you want to prevent such a situation from happening. Use an appropriate dollar condition on Most likely however you want to prevent such a situation from happening. Use an appropriate dollar condition on the equation such that this equation is not generated. the equation such that this equation is not generated. -