Originally posted by: SystemAdmin

[tksung said:]

HI!
I am not good in programming , hope this question is not too trivial.  Really need some help.


  I am trying to retrive the rhs valuse of a presolved LP through
  CPXgetredlp and CPXgetrhs.

In the manual
The routine CPXgetredlp returns a pointer for the presolved problem.
    I am using function:
CPXPUBLIC CPXgetredlp(CPXCENVptr env, CPXCLPptr lp, CPXCLPptr * redlp_p)
  where Parameters:
  env: A pointer to the CPLEX environment, as returned by CPXopenCPLEX.

    lp: A pointer to a CPLEX LP problem object, as returned by CPXcreateprob.

  redlp_p: A pointer to receive the problem object pointer that results when presolve has been applied to the LP problem object.

and The routine CPXgetrhs is used to access the right-hand side coefficients for a range of constraints in a CPLEX problem object.
    I am using function:
CPXgetrhs(CPXCENVptr env, CPXCLPptr lp, double * rhs, int begin, int end)
where Parameters:
    env: A pointer to the CPLEX environment as returned by CPXopenCPLEX.

    lp: A pointer to a CPLEX problem object as returned by CPXcreateprob.

    rhs: An array where the specified right-hand side coefficients are to be returned. 
   
-----------------------
My question is
Does "lp"  parameter in CPXgetrhs(env,  lp,  rhs, begin, end) have to be "returned by CPXcreateprob", as mentioned in manual?

Can I use redlp_p, instead of lp, in CPXgetrhs(env,  redlp_p,  rhs, begin, end) where redlp_p is returned in CPXgetredlp(env,  lp, redlp_p)

The redlp_p is  "a pointer to receive the problem object pointer that results when presolve has been applied to the LP problem object",  not  "returned by CPXcreateprob".

I did this in my codes try to get RHS of the presolved problem, but it did not wrok.
Do my codes have bugs?  or redlp_p cant be passed to CPXgetrhs as the lp parameter?

Thanks!




#CPLEXOptimizers
#DecisionOptimization

Originally posted by: SystemAdmin

[MaryFenelon said:]

You should use

  CPXCLPptr redlp;
 
  CPXgetredlp (env, lp, &redlp);
  CPXgetrhs (env,  redlp,  rhs, begin, end);

The "&" notation tells C to use the address of the argument, which makes "&redlp" a pointer to a CPXLPptr object, which is what "CPXCLPptr *" means.  I still think the best C book is Kernighan & Ritchie's book; give it a look.


#CPLEXOptimizers
#DecisionOptimization