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[Help-glpk] Is this a bug I see before me?
From: |
Nigel Galloway |
Subject: |
[Help-glpk] Is this a bug I see before me? |
Date: |
Mon, 2 Mar 2009 16:53:43 +0300 |
Is this a bug I see before me, or the mere manifestation of a new feature?
Running a variation on my favorite mathprog:
param a, integer;
param b, integer;
param guess, integer;
var x, integer;
var y, integer;
s1: 1 <= a*x+b*y <= guess;
solve;
printf "x= %i y= %i a*x+b*y= %i\n",x,y,a*x+b*y;
data;
param a := 75;
param b := 15;
param guess := 14;
end;
Produces:
address@hidden:~/myGLPK/mods$ /opt/glpk.4.36/bin/glpsol --math t1.mod
Reading model section from t1.mod...
Reading data section from t1.mod...
20 lines were read
Generating s1...
Model has been successfully generated
ipp_basic_tech: 0 row(s) and 0 column(s) removed
ipp_reduce_bnds: 1 pass(es) made, 0 bound(s) reduced
ipp_basic_tech: 0 row(s) and 0 column(s) removed
ipp_reduce_coef: 1 pass(es) made, 0 coefficient(s) reduced
glp_intopt: presolved MIP has 1 row, 2 columns, 2 non-zeros
glp_intopt: 2 integer columns, none of which are binary
Scaling...
A: min|aij| = 1.500e+01 max|aij| = 7.500e+01 ratio = 5.000e+00
GM: min|aij| = 1.000e+00 max|aij| = 1.000e+00 ratio = 1.000e+00
EQ: min|aij| = 1.000e+00 max|aij| = 1.000e+00 ratio = 1.000e+00
2N: min|aij| = 9.375e-01 max|aij| = 1.172e+00 ratio = 1.250e+00
Crashing...
Size of triangular part = 1
Solving LP relaxation...
* 0: obj = 0.000000000e+00 infeas = 0.000e+00 (0)
OPTIMAL SOLUTION FOUND
Integer optimization begins...
+ 0: mip = not found yet >= -inf (1; 0)
+398442: mip = not found yet >= 0.000000000e+00 (2; 0)
+797967: mip = not found yet >= 0.000000000e+00 (2; 0)
+1194797: mip = not found yet >= 0.000000000e+00 (2; 0)
+1593432: mip = not found yet >= 0.000000000e+00 (2; 0)
+1991942: mip = not found yet >= 0.000000000e+00 (2; 0)
+2389899: mip = not found yet >= 0.000000000e+00 (2; 0)
+2788043: mip = not found yet >= 0.000000000e+00 (2; 0)
+3186585: mip = not found yet >= 0.000000000e+00 (2; 0)
+3584825: mip = not found yet >= 0.000000000e+00 (2; 0)
+3982340: mip = not found yet >= 0.000000000e+00 (2; 0)
+3997277: >>>>> 0.000000000e+00 >= 0.000000000e+00 0.0% (2; 0)
+3997277: mip = 0.000000000e+00 >= tree is empty 0.0% (0; 3)
INTEGER OPTIMAL SOLUTION FOUND
Time used: 50.2 secs
Memory used: 0.1 Mb (146581 bytes)
x= 1333334 y= -6666670 a*x+b*y= 0
Model has been successfully processed
address@hidden:~/myGLPK/mods$
Ever since 0 has been considered a number, 1 <= 0 <= 14 has been considered
false.
As the only constraint is that 1 <= a*x+b*y <= 14, and a*x+b*y = 0 is not so
constrained, is the optimistic conclusion of the model misconceived?
- [Help-glpk] Is this a bug I see before me?,
Nigel Galloway <=