Sunday, May 1, 2016

LP solve problems with tiny model

From this post:

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Model name:  'LPSolver' - run #1
Objective:   Maximize(R0)

SUBMITTED
Model size:        3 constraints,       4 variables,            6 non-zeros.
Sets:                                   0 GUB,                  0 SOS.

Using DUAL simplex for phase 1 and PRIMAL simplex for phase 2.
The primal and dual simplex pricing strategy set to 'Devex'.

Relaxed solution                   4 after          4 iter is B&B base.

Feasible solution                  2 after          6 iter,         3 nodes (gap 40.0%)

Optimal solution                   2 after          7 iter,         4 nodes (gap 40.0%).
Excellent numeric accuracy ||*|| = 0

MEMO: lp_solve version 5.5.2.0 for 32 bit OS, with 64 bit REAL variables.
In the total iteration count 7, 1 (14.3%) were bound flips.
There were 2 refactorizations, 0 triggered by time and 0 by density.
... on average 3.0 major pivots per refactorization.
The largest [LUSOL v2.2.1.0] fact(B) had 8 NZ entries, 1.0x largest basis.
The maximum B&B level was 3, 0.8x MIP order, 3 at the optimal solution.
The constraint matrix inf-norm is 3, with a dynamic range of 3.
Time to load data was 0.001 seconds, presolve used 0.010 seconds,
... 0.020 seconds in simplex solver, in total 0.031 seconds
.