Huge memory usage difference

[Domingo Alvarez Duarte]

Hello !

I just found a class of models that can exhibit a huge memory usage 
difference depending on if we add or not add parameter missing values 
when there is a default value declaration for then.

See this model for example 
https://github.com/mingodad/GLPK/commit/539dd9774829dee4a0b8c8199a9d2b94a3c7d9cb:

GLPK-4.65 from pacakage manager    69.85s    3001.9 Mb    1x 1x

GLPK-4.65 with several optimizations    26.02s    1506.0 Mb 0.37x    0.5x

GLPK-4.65 prev + no param add missing    16.36s    21.2 Mb Mb 0.23x    
0.007x

This huge difference is due to this changes 
https://github.com/mingodad/GLPK/commit/70d4ad7e97cdb34ee6348c864bd3a941cdb0d422 
.

If you have big models/data and can test then with the master branch of 
https://github.com/mingodad/GLPK and report your results I would 
appreciate it and hope this can lead to more performance improvements in 
GMPL/GLPK.

Notice right now the changes mainly affect GMPL model/data generation 
not solver/solving the generated problem.

====

/usr/bin/time glpsol-from-package-manager -m mem-default.mod -d 
mem-default.dat
GLPSOL: GLPK LP/MIP Solver, v4.65
Parameter(s) specified in the command line:
 -m mem-default.mod -d mem-default.dat
Reading model section from mem-default.mod...
mem-default.mod:23: warning: unexpected end of file; missing end 
statement inserted
23 lines were read
Reading data section from mem-default.dat...
mem-default.dat:32660: warning: unexpected end of file; missing end 
statement inserted
32660 lines were read
Generating omax...
Generating c1...
Generating c2...
Model has been successfully generated
GLPK Integer Optimizer, v4.65
13589 rows, 14037 columns, 42743 non-zeros
449 integer variables, all of which are binary
Preprocessing...
9 constraint coefficient(s) were reduced
4056 rows, 4495 columns, 12792 non-zeros
448 integer variables, all of which are binary
Scaling...
 A: min|aij| =  1.310e-05  max|aij| =  2.660e+02  ratio = 2.031e+07
GM: min|aij| =  7.228e-02  max|aij| =  1.384e+01  ratio = 1.914e+02
EQ: min|aij| =  5.224e-03  max|aij| =  1.000e+00  ratio = 1.914e+02
2N: min|aij| =  2.620e-03  max|aij| =  1.750e+00  ratio = 6.679e+02
Constructing initial basis...
Size of triangular part is 4056
Solving LP relaxation...
GLPK Simplex Optimizer, v4.65
4056 rows, 4495 columns, 12792 non-zeros
*     0: obj =   1.000000000e+00 inf =   0.000e+00 (2721)
*  3122: obj =   5.173823646e+02 inf =   0.000e+00 (0) 3
OPTIMAL LP SOLUTION FOUND
Integer optimization begins...
Long-step dual simplex will be used
+  3122: mip =     not found yet <=              +inf (1; 0)
+  3122: >>>>>   5.173823646e+02 <= 5.173823646e+02   0.0% (1; 0)
+  3122: mip =   5.173823646e+02 <=     tree is empty   0.0% (0; 1)
INTEGER OPTIMAL SOLUTION FOUND
Time used:   0.3 secs
Memory used: 3001.9 Mb (3147772544 bytes)
69.85user 0.88system 1:10.73elapsed 99%CPU (0avgtext+0avgdata 
3083108maxresident)k
0inputs+0outputs (0major+770102minor)pagefaults 0swaps

====

====

/usr/bin/time myglpsol-with-several-optmizations -m mem-default.mod -d 
mem-default.dat
GLPSOL: GLPK LP/MIP Solver, v4.65
Parameter(s) specified in the command line:
 -m mem-default.mod -d mem-default.dat
Reading model section from mem-default.mod...
mem-default.mod:23: warning: unexpected end of file; missing end 
statement inserted
23 lines were read
Reading data section from mem-default.dat...
mem-default.dat:32660: warning: unexpected end of file; missing end 
statement inserted
32660 lines were read
Generating omax...
Generating c1...
Generating c2...
Model has been successfully generated
GLPK Integer Optimizer, v4.65
13589 rows, 14037 columns, 42743 non-zeros
449 integer variables, all of which are binary
Preprocessing...
9 constraint coefficient(s) were reduced
4056 rows, 4495 columns, 12792 non-zeros
448 integer variables, all of which are binary
Scaling...
 A: min|aij| =  1.310e-05  max|aij| =  2.660e+02  ratio = 2.031e+07
GM: min|aij| =  7.228e-02  max|aij| =  1.384e+01  ratio = 1.914e+02
EQ: min|aij| =  5.224e-03  max|aij| =  1.000e+00  ratio = 1.914e+02
2N: min|aij| =  2.620e-03  max|aij| =  1.750e+00  ratio = 6.679e+02
Constructing initial basis...
Size of triangular part is 4056
Solving LP relaxation...
GLPK Simplex Optimizer, v4.65
4056 rows, 4495 columns, 12792 non-zeros
*     0: obj =   1.000000000e+00 inf =   0.000e+00 (2721)
*  3122: obj =   5.173823646e+02 inf =   0.000e+00 (0) 3
OPTIMAL LP SOLUTION FOUND
Integer optimization begins...
Long-step dual simplex will be used
+  3122: mip =     not found yet <=              +inf (1; 0)
+  3122: >>>>>   5.173823646e+02 <= 5.173823646e+02   0.0% (1; 0)
+  3122: mip =   5.173823646e+02 <=     tree is empty   0.0% (0; 1)
INTEGER OPTIMAL SOLUTION FOUND
Time used:   0.3 secs
Memory used: 1506.0 Mb (1579147056 bytes)
26.02user 0.57system 0:26.61elapsed 99%CPU (0avgtext+0avgdata 
1547792maxresident)k
1952inputs+0outputs (9major+386354minor)pagefaults 0swaps

====

====

/usr/bin/time myglpsol-master -m mem-default.mod -d mem-default.dat
GLPSOL: GLPK LP/MIP Solver, v4.65
Parameter(s) specified in the command line:
 -m mem-default.mod -d mem-default.dat
Reading model section from mem-default.mod...
mem-default.mod:23: warning: unexpected end of file; missing end 
statement inserted
23 lines were read
Reading data section from mem-default.dat...
mem-default.dat:32660: warning: unexpected end of file; missing end 
statement inserted
32660 lines were read
Generating omax...
Generating c1...
Generating c2...
Model has been successfully generated
GLPK Integer Optimizer, v4.65
13589 rows, 14037 columns, 42743 non-zeros
449 integer variables, all of which are binary
Preprocessing...
9 constraint coefficient(s) were reduced
4056 rows, 4495 columns, 12792 non-zeros
448 integer variables, all of which are binary
Scaling...
 A: min|aij| =  1.310e-05  max|aij| =  2.660e+02  ratio = 2.031e+07
GM: min|aij| =  7.228e-02  max|aij| =  1.384e+01  ratio = 1.914e+02
EQ: min|aij| =  5.224e-03  max|aij| =  1.000e+00  ratio = 1.914e+02
2N: min|aij| =  2.620e-03  max|aij| =  1.750e+00  ratio = 6.679e+02
Constructing initial basis...
Size of triangular part is 4056
Solving LP relaxation...
GLPK Simplex Optimizer, v4.65
4056 rows, 4495 columns, 12792 non-zeros
*     0: obj =   1.000000000e+00 inf =   0.000e+00 (2721)
*  3122: obj =   5.173823646e+02 inf =   0.000e+00 (0) 3
OPTIMAL LP SOLUTION FOUND
Integer optimization begins...
Long-step dual simplex will be used
+  3122: mip =     not found yet <=              +inf (1; 0)
+  3122: >>>>>   5.173823646e+02 <= 5.173823646e+02   0.0% (1; 0)
+  3122: mip =   5.173823646e+02 <=     tree is empty   0.0% (0; 1)
INTEGER OPTIMAL SOLUTION FOUND
Time used:   0.2 secs
Memory used: 21.2 Mb (22256384 bytes)
16.36user 0.02system 0:16.39elapsed 99%CPU (0avgtext+0avgdata 
24516maxresident)k
2600inputs+0outputs (11major+7226minor)pagefaults 0swaps

====

Cheers !