[Bug-glpk] slow model generation

[Zewei Chen]

Hi,

I found glpk model generation to be quite slow.
It's about 15 times slower compared to the
ampl interpreter from cplex.  Is that well-known?
Are there obvious work-arounds (to reduce model
generation time in general, not just this example)?  
Is this related to any known performance bugs that
will be fixed in the next release?

Thanks for your insights.

Zewei

Here's an example model file and summary of
the comparison results (transcript attached):

$ cat t3.mod

set X := 1.._SIZE_;
set Y := 1.._SIZE_;
set Z := 1.._SIZE_;
display sum {x in X, y in Y, z in Z} 1;
end;

$ for s in 50 100 200 400 800; do sed -e "s/_SIZE_/$s/" t3.mod > t.mod; 
time ampl t.mod; done
$ for s in 50 100 200 400 800; do sed -e "s/_SIZE_/$s/" t3.mod > t.mod; 
time glpsol -m t.mod; done

size    size^3        ampl time    glpk time
----------------------------------------------------
50    125000        0m0.135s    0m0.222s
100    1e+06        0m0.144s    0m1.491s
200    8e+06        0m0.913s    0m11.558s
400    6.4e+07        0m6.916s    1m48.853s
800    5.12e+08    0m55.370s    13m59.423s

$ cat t3.mod
set X := 1.._SIZE_;
set Y := 1.._SIZE_;
set Z := 1.._SIZE_;
display sum {x in X, y in Y, z in Z} 1;

end;


$ for s in 50 100 200 400 800; do sed -e "s/_SIZE_/$s/" t3.mod > t.mod; time 
ampl t.mod; done
+ sed -e s/_SIZE_/50/ t3.mod
+ ampl t.mod
sum{x in X, y in Y, z in Z} 1 = 125000


real    0m0.135s
user    0m0.020s
sys     0m0.000s
+ sed -e s/_SIZE_/100/ t3.mod
+ ampl t.mod
sum{x in X, y in Y, z in Z} 1 = 1e+06


real    0m0.144s
user    0m0.110s
sys     0m0.000s
+ sed -e s/_SIZE_/200/ t3.mod
+ ampl t.mod
sum{x in X, y in Y, z in Z} 1 = 8e+06


real    0m0.913s
user    0m0.860s
sys     0m0.000s
+ sed -e s/_SIZE_/400/ t3.mod
+ ampl t.mod
sum{x in X, y in Y, z in Z} 1 = 6.4e+07


real    0m6.916s
user    0m6.910s
sys     0m0.000s
+ sed -e s/_SIZE_/800/ t3.mod
+ ampl t.mod
sum{x in X, y in Y, z in Z} 1 = 5.12e+08


real    0m55.370s
user    0m55.320s
sys     0m0.000s
$ for s in 50 100 200 400 800; do sed -e "s/_SIZE_/$s/" t3.mod > t.mod; time 
glpsol -m t.mod; done
+ sed -e s/_SIZE_/50/ t3.mod
+ glpsol -m t.mod
Reading model section from t.mod...
7 lines were read
Display statement at line 4
125000
Model has been successfully generated
Problem has no rows

real    0m0.222s
user    0m0.180s
sys     0m0.000s
+ sed -e s/_SIZE_/100/ t3.mod
+ glpsol -m t.mod
Reading model section from t.mod...
7 lines were read
Display statement at line 4
1000000
Model has been successfully generated
Problem has no rows

real    0m1.491s
user    0m1.480s
sys     0m0.000s
+ sed -e s/_SIZE_/200/ t3.mod
+ glpsol -m t.mod
Reading model section from t.mod...
7 lines were read
Display statement at line 4
8000000
Model has been successfully generated
Problem has no rows

real    0m11.558s
user    0m11.560s
sys     0m0.000s
+ sed -e s/_SIZE_/400/ t3.mod
+ glpsol -m t.mod
Reading model section from t.mod...
7 lines were read
Display statement at line 4
64000000
Model has been successfully generated
Problem has no rows

real    1m48.853s
user    1m48.810s
sys     0m0.010s
+ sed -e s/_SIZE_/800/ t3.mod
+ glpsol -m t.mod
Reading model section from t.mod...
7 lines were read
Display statement at line 4
512000000
Model has been successfully generated
Problem has no rows

real    13m59.423s
user    13m59.470s
sys     0m0.000s


+ cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 2
model name      : Intel(R) Pentium(R) 4 CPU 2.40GHz
stepping        : 9
cpu MHz         : 2394.061
cache size      : 512 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov 
pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm
bogomips        : 4771.02

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 15
model           : 2
model name      : Intel(R) Pentium(R) 4 CPU 2.40GHz
stepping        : 9
cpu MHz         : 2394.061
cache size      : 512 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 2
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov 
pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm
bogomips        : 4784.12