Solver delivers wrong answer when 2 constraints are close

Hi.
I've found a strange behaviour in glpk which I don't know how to fix nor
how to contour it. It seems like GLPK can't distinguish constraints that
differs from about 1e-4.

Follows simple examples that explain and reproduce the problem.

*The first model gives the desired answer (x = 1.0001):*

*param min_bound default 0;*


*var x >= 0;minimize y: x;*










*  s.t. PART_MIN_X: x >= 1 + min_bound;solve;display min_bound;display x; #
EXPECTED RESULT: X ==  1.0001data;param min_bound := 1e-4;end;*
*_____________________________________*
*OUTPUT:*
*x.val = 1.0001*
*_____________________________________  *

*Now, if I add a second constraint "close" to the first one, the solver
will deliver an answer that is actually infeasible:*

*param min_bound default 0;*


*var x >= 0;minimize y: x;*



*s.t. LIM_INF_X: x >= 1;*







*s.t. PART_MIN_X: x >= 1 + min_bound;solve;display min_bound;display x; #
EXPECTED RESULT: X ==  1.0001data;param min_bound := 1e-4;end;*
*_____________________________________*
*OUTPUT:*
x.val = 1
*_____________________________________  *

*If I change the "min_bound" parameter to 1e-2, the second model works as
expected (x = 1.01):*

*param min_bound default 0;*



*var x >= 0;minimize y: x;*



*s.t. LIM_INF_X: x >= 1;*

*s.t. PART_MIN_X: x >= 1 + min_bound;solve;*





*display x; # EXPECTED RESULT: X ==  1.01data;param min_bound := 1e-2;end;*
*_____________________________________*
*OUTPUT:*
x.val = 1.01
*_____________________________________  *


Att,

*Thiago H. Neves*
(31) 98608-0666