Re: Solver with Constraints failure

---Reply to mail from Afonso Celso Medina about Solver with Constraints failure


When I changed my 1.4.2 gnumeric (linux) to the 1.5.2 version(win32), I
have noticed that the Solver tool didn't work never more. Using the
Program report, I could discover that it is not a problem in Target
Cell, but there is a problem in Constraints parsing. Now, all my
correct old models runs to Unbounded Solution.

Hi, Afonso,

  could You please, supply a small representative example, 
of LP program, where your problem is demonstrated?

  I can confirm, that in following problem:

            x1 + x2

Subject to:

             2 x1+ x2   <= 2
              x1 + 2 x2 <= 2

(x1, x2 >=0)
the constraints are parsed incorrectly as:

            -x1 + x2  <= 0
          -2 x1 +2 x2 <= 0

  Solver seems to be broken in 1.5.2.

  I suggested patches for working with 
affine expressions of type c0 + sum(i=1..n, c_i * x_i),
they worked in 1.4.3; hope someone of Gnumeric developers
could quickly identify the cause of solver failures in 1.5 series, 
altough I am not sure the problem is connected 
with my suggestions. 
  I will try to compile myself the sources of 1.5.2 and see,
if I can do something with the mentioned problem.


Michal Kaukic                                  (mike frcatel fri utc sk)         
Dept. of Math. Methods, Fac. of Manag. & Informatics
University of Zilina,   Slovak Republic

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