Re: [Help-glpk] How I do for write a restriction with binary variables, with dynamic restriction

[Andrew Makhorin]

> I have a model which  has the next lines
> 
> set J:={1..3}; #Número de centrales hidroeléctricas del sistema
> set T:={1..3}; #Número de periodos del horizonte temporal
> 
> param Pmin{j in J, t in T};
> param Pmax{j in J, t in T};
> var v{j in J, t in T}, binary, >=0;
> #constraint:
> prodTer{j in J, t in T}: Pmin[j,t]*v[j,t] <= p[j,t] <= Pmax[j,t]*v[j,t];
> 
> when I try to compile appear the next error:
> 
> "leftmost expression in double inequality cannot be linear form
> Context:  , t in T } : Pmin [ j , t ] * v [ j , t ] <= p [ j , t ] <=
> MathProg model processing error"
> 
> What's wrong in the restriction?

Split your double inequality into two single inequalities:

prodTer1{j in J, t in T}: Pmin[j,t]*v[j,t] <= p[j,t];
prodTer2{j in J, t in T}: p[j,t] <= Pmax[j,t]*v[j,t];

> 
> On the other hand, if I have a restriction like:
> 
> ContHidrica {i in I, t in T}: V[i,t] = V[i,t-1] + r[i,t]
> 
> How can I  supply the value V[i,0] at the begining?  or If I have
> 
> rampaBaj{j in J, t in T}: p[j,t] - p[j,t+1] <= X[j]
> 
> How  can I  for manipulate the subscripts to avoid  go beyond limits?
> 

Use predicates on specifying subscript domains, e.g.

ContHidrica {i in I, t in T: t != 0}: V[i,t] = V[i,t-1] + r[i,t]
rampaBaj{j in J, t in T: t != card(T)}: p[j,t] - p[j,t+1] <= X[j]

For more details see the language reference. See also examples included
in subdirectory glpk/examples.