Hello,
I have a large MIP model (lots of data) for a location - allocation
problem. The model fails due to lack of memory, so I have reduced the
data set to validate the model.
I am using a Windows XP 32 bit with 4GB ram (usable is <3GB after system
resources - as I understand this stuff). I will be acquiring a 64bit
workstation with lots more memory.
I have used the "build MPS" option in Gusek, creating a 28Mb file - if
that provides any indication of the size of the model.
Since having trouble some time ago reading input data from MS Access, I
have used the update provided by Xypron successfully (thanks very much
and my apologies for not having thanked you earlier).
Now, however, writing the output causes a lack of memory error and the
model fails even with the reduced data set. I have been watching the
memory monitor through Windows Task Manager and note that the reduced
data set finds an integer (they are all binary) optimal solution after
about 2500 secs at which time the reported available memory is c.c.
1.9GB.
When I include the Access table output the memory reduces rapidly and
the program fails. The following is one of the Access output table
syntax (which I assume is correct, because the smaller output tables
update correctly).
table result_flow_pl_dc {pl in PLANTS, ma in MACHINES, dc in WAREHOUSES,
pm in PRODUCTS:flow_pl_dc[pl,ma,dc,pm]>0} OUT "ODBC"
'DSN=glpk_Yorke'
'DELETE FROM glpk_flow_pl_dc;'
'INSERT INTO glpk_flow_pl_dc VALUES (?,?,?,?,?)':
pl~PL, ma~MACHINE, dc~DC, pm~MATERIAL,
flow_pl_dc[pl,ma,dc,pm]~QTY;
I have checked and confirmed that the Access table has the same field
names and the following is the table structure / data types:
PL Number - Long Integer (which is the same as the
input data
MACHINE Number - Long Integer (which is the same as the input
data
DC Number - Long Integer (which is the same as the
input data
MATERIAL Text - 50 (the input data table has 255, but the
actual maximum length is 18).
QTY Number - Double (same as the input table)
Is this problem expected or is there something that I can do to get it
to complete?
The reason that I am doing this is that the output file that I get from
--output is very large, with many zeros. I adopted this approach after
reading some of the help archives. If there are better / preferred
methods, I would be grateful for any advice / suggestions.
(I have tried the csv output with the same outcome).
Regards, Alex
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