gams:undefined_real_power

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gams:undefined_real_power [2008/10/24 15:45] (current) support created |
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+ | ====== UNDEFINED REAL POWER ====== | ||

+ | <code> | ||

+ | **** ERRORS(S) IN EQUATION XXX(S,M) | ||

+ | 1 INSTANCE OF - UNDEFINED REAL POWER (RETURNED 0.0E+00) | ||

+ | </code> | ||

+ | Without seeing the definition of equation XXX, it is not possible to say what the problem is exactly, but I can speculate a bit. This type of message is often the result of raising a variable to a power less than one, and trying to evaluate this with a zero or negative argument. For example, | ||

+ | |||

+ | ''x**0.5'' is not defined for ''x=-.1'', and if ''x = 0,'' the derivative is not defined, so there is still going to be an evaluation error. | ||

+ | |||

+ | One common approach to fixing this is to place a bound on the variable in question (say ''x.lo = 1e-5'') and make sure that none of these bounds are active at the solution to the model. | ||

+ | |||

+ | If you are raising an expression to a power, you can either add an equation to bound that expression, or set this expression to a new variable you introduce (via a new equation) and bound the new variable as above. |

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gams/undefined_real_power.txt ยท Last modified: 2008/10/24 15:45 by support