[Help-glpk] very small "infeas=" values in glpsol

[Yaron Kretchmer]

Hi All.
I'm solving a semiconductor routing problem, and running glpsol, I'm
running into very long solution times, accompanied by very small
infeasibility numbers.

Some questions:
*) What do the infeasibility numbers mean? Does it matter that they're
very small?
*) Is there a way/runtime-option I can use to speed up the solution times?

Thanks
Yaron


Here's an example:
----------------Begin Example---------------------------------------------------
>c:\gusek\glpsol.exe --mostf -m ".."    --cuts
GLPSOL: GLPK LP/MIP Solver 4.39
Reading model section from Sep26_Giles_mcf.mod...
Reading data section from Sep26_Giles_mcf.mod...
3856 lines were read
...
Generating obj...
Model has been successfully generated
ipp_basic_tech:  276317 row(s) and 221492 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 58300 rows, 34866 columns, 163658 non-zeros
glp_intopt: 34866 integer columns, all of which are binary
Scaling...
 A: min|aij| = 1.000e+000  max|aij| = 1.000e+000  ratio = 1.000e+000
Problem data seem to be well scaled
Constructing initial basis...
Size of triangular part = 58300
Solving LP relaxation...
      0: obj =  0.000000000e+000  infeas = 1.532e+003 (0)
   ...
* 20600: obj =  2.330000000e+002  infeas = 2.545e-015 (0)
* 20682: obj =  2.400000000e+002  infeas = 2.643e-015 (0)
OPTIMAL SOLUTION FOUND
Integer optimization begins...
Gomory's cuts enabled
MIR cuts enabled
Cover cuts enabled
Clique cuts enabled
Creating the conflict graph...
The conflict graph is either empty or too big
+ 20682: mip =     not found yet <=              +inf        (1; 0)
| 22200: obj =  2.400000000e+002  infeas = 1.517e-013 (0)
| 22400: obj =  2.400000000e+002  infeas = 7.154e-014 (0)
| 22600: obj =  2.400000000e+002  infeas = 5.790e-016 (0)
| 22800: obj =  2.400000000e+002  infeas = 2.508e-014 (0)
| 23000: obj =  2.400000000e+002  infeas = 3.359e-014 (0)
...
...
+124073: mip =     not found yet <=  2.400000000e+002        (14; 9)
Time used: 999.5 secs.  Memory used: 763.1 Mb.
|125200: obj =  2.400000000e+002  infeas = 0.000e+000 (709)
|125400: obj =  2.400000000e+002  infeas = 5.262e-014 (708)
|125600: obj =  2.400000000e+002  infeas = 2.227e-015 (708)
|125800: obj =  2.400000000e+002  infeas = 0.000e+000 (708)
|126000: obj =  2.400000000e+002  infeas = 0.000e+000 (708)
|126200: obj =  2.400000000e+002  infeas = 8.301e-014 (698)
|126202: obj =  2.400000000e+002  infeas = 8.301e-014 (698)
+126202: mip =     not found yet <=  2.400000000e+002        (14; 9)
|127400: obj =  2.400000000e+002  infeas = 0.000e+000 (693)
|127600: obj =  2.400000000e+002  infeas = 0.000e+000 (693)
|127800: obj =  2.400000000e+002  infeas = 0.000e+000 (693)
|128000: obj =  2.400000000e+002  infeas = 0.000e+000 (693)
|128200: obj =  2.400000000e+002  infeas = 0.000e+000 (693)
|128400: obj =  2.400000000e+002  infeas = 4.223e-014 (693)
|128600: obj =  2.400000000e+002  infeas = 0.000e+000 (681)
|128800: obj =  2.400000000e+002  infeas = 0.000e+000 (677)
|129000: obj =  2.400000000e+002  infeas = 0.000e+000 (677)
|129044: obj =  2.400000000e+002  infeas = 0.000e+000 (677)
+129044: mip =     not found yet <=  2.400000000e+002        (14; 9)
|130400: obj =  2.400000000e+002  infeas = 0.000e+000 (664)
|130600: obj =  2.400000000e+002  infeas = 0.000e+000 (663)
|130800: obj =  2.400000000e+002  infeas = 1.988e-014 (662)
|131000: obj =  2.400000000e+002  infeas = 0.000e+000 (662)
|131075: obj =  2.400000000e+002  infeas = 0.000e+000 (662)
+131075: mip =     not found yet <=  2.400000000e+002        (14; 9)
Time used: 1065.0 secs.  Memory used: 763.3 Mb.
|132400: obj =  2.400000000e+002  infeas = 1.216e-014 (659)
|132600: obj =  2.400000000e+002  infeas = 0.000e+000 (637)
|132800: obj =  2.400000000e+002  infeas = 0.000e+000 (631)
|133000: obj =  2.400000000e+002  infeas = 0.000e+000 (631)
|133102: obj =  2.400000000e+002  infeas = 0.000e+000 (631)
+133102: mip =     not found yet <=  2.400000000e+002        (15; 9)
|134400: obj =  2.400000000e+002  infeas = 0.000e+000 (719)
|134600: obj =  2.400000000e+002  infeas = 0.000e+000 (716)
|134800: obj =  2.400000000e+002  infeas = 1.084e-014 (716)
|135000: obj =  2.400000000e+002  infeas = 0.000e+000 (714)
|135200: obj =  2.400000000e+002  infeas = 3.699e-014 (710)
|135275: obj =  2.400000000e+002  infeas = 0.000e+000 (709)
+135275: mip =     not found yet <=  2.400000000e+002        (16; 9)
|136600: obj =  2.400000000e+002  infeas = 0.000e+000 (629)
|136800: obj =  2.400000000e+002  infeas = 5.870e-015 (629)
|137000: obj =  2.400000000e+002  infeas = 0.000e+000 (629)
|137045: obj =  2.400000000e+002  infeas = 4.670e-014 (629)
+137045: mip =     not found yet <=  2.400000000e+002        (15; 10)
|138400: obj =  2.400000000e+002  infeas = 0.000e+000 (627)
|138450: obj =  2.400000000e+002  infeas = 0.000e+000 (627)
+138450: mip =     not found yet <=  2.400000000e+002        (15; 10)
Time used: 1133.6 secs.  Memory used: 763.6 Mb.
|139736: obj =  2.400000000e+002  infeas = 0.000e+000 (627)
+139736: mip =     not found yet <=  2.400000000e+002        (15; 10)
|141000: obj =  2.400000000e+002  infeas = 0.000e+000 (623)
|141200: obj =  2.400000000e+002  infeas = 0.000e+000 (623)
|141400: obj =  2.400000000e+002  infeas = 0.000e+000 (623)
|141513: obj =  2.400000000e+002  infeas = 4.446e-014 (623)
+141513: mip =     not found yet <=  2.400000000e+002        (15; 10)
|142800: obj =  2.400000000e+002  infeas = 0.000e+000 (623)
|142817: obj =  2.400000000e+002  infeas = 0.000e+000 (623)
+142817: mip =     not found yet <=  2.400000000e+002        (15; 10)
|144000: obj =  2.400000000e+002  infeas = 0.000e+000 (623)
|144200: obj =  2.400000000e+002  infeas = 0.000e+000 (622)
|144400: obj =  2.400000000e+002  infeas = 0.000e+000 (618)
|144495: obj =  2.400000000e+002  infeas = 0.000e+000 (618)
+144495: mip =     not found yet <=  2.400000000e+002        (16; 10)
|145800: obj =  2.340000000e+002  infeas = 0.000e+000 (972)
|146000: obj =  2.340000000e+002  infeas = 0.000e+000 (972)
|146200: obj =  2.340000000e+002  infeas = 0.000e+000 (971)
|146367: obj =  2.340000000e+002  infeas = 0.000e+000 (971)
+146367: mip =     not found yet <=  2.400000000e+002        (17; 10)
Time used: 1207.9 secs.  Memory used: 763.8 Mb.
|147600: obj =  2.400000000e+002  infeas = 0.000e+000 (707)
|147800: obj =  2.400000000e+002  infeas = 6.921e-014 (707)
|148000: obj =  2.400000000e+002  infeas = 0.000e+000 (707)
|148200: obj =  2.400000000e+002  infeas = 0.000e+000 (707)
|148234: obj =  2.400000000e+002  infeas = 0.000e+000 (707)
+148234: mip =     not found yet <=  2.400000000e+002        (16; 11)
|149400: obj =  2.400000000e+002  infeas = 1.332e-014 (700)
|149600: obj =  2.400000000e+002  infeas = 0.000e+000 (699)
--------------------End
Example---------------------------------------------------------------------------