Re: st: Operations Research Bin-packing Problem

[dicke126@umn.edu]

Happy Holidays Statalisters,

Here is the code I'm using for the problem described below. It works except 
for failing to carry forward the "new" remaining job time. As a result I 
end up with most of my jobs "scheduled" in the first block except for those 
that are too large for it. Jobs that are too large are compared with 
succeeding blocks until one is that it fits in.
local obsno = 0
while `obsno' <= _N {
local ++obsno
foreach day of numlist 1/5 {
foreach block of numlist 1/2 {
replace RemainingDay`day'Block`block'=Day`day'Block`block' if logid==000001
replace RemainingDay`day'Block`block'=RemainingDay`day'Block`block'[_n-1] 
if logid!=000001
local priorday=`day'-1
replace D`day'B`block'=.b if schedmins>RemainingDay`day'Block`block'
replace D`day'B`block' = logid if D`day'B`block'==. & 
D`priorday'B`block'!=. & D`priorday'B`block'!=logid & 
schedmins<RemainingDay`day'Block`block'
replace D`day'B2 =.f if D`day'B1==logid
replace D`day'B`block'=.f if D`priorday'B`block'==logid | 
D`priorday'B`block'==.f
replace 
RemainingDay`day'Block`block'=RemainingDay`day'Block`block'-schedmins if 
D`day'B`block'==logid
}
}
}


Any assistance in getting the adjusted time to to be transferred forward 
before the next job is scheduled would be appreciated.
Thank you,
Christopher Dickerson
PhD Student
University of Minnesota


On Dec 16 2010, dicke126@umn.edu wrote:

> I am trying to develop an initial solution to a bin-packing problem using 
> Stata.
> I have 2 time blocks (different lengths) over a series of 5 days (10 total 
> blocks). Various processes of differing lengths need to be scheduled into 
> the time blocks depending on how much time remains available.
> As far as I can tell I need to loop over observations one at a time 
> completing all the calculations in one observation before moving forward. 
> This is because scheduling in one observation changes the available time 
> for all remaining observations.
> In plain language:
1: schedule process in block if estimated process time < time available 
for
> block (initially first fit but in future some form of best fit)
2: do not schedule in additional blocks (or replace as some form of 
missing
> if the process is scheduled in a prior block)
> 3: reduce time available in block scheduled by estimated processing time 
> for all remaining attempts to schedule a process
> I can get it to run in such a fashion that:
>
> 1: all processes get scheduled in the first block on the first day because 
> the time remaining in that block is not adjusted before the comparison 
> between available time and estimated processing time occurs.
> 2: or the first observation works correctly, the available time is 
> correctly carried forward to the second (and only the second) observation 
> but the comparison and scheduling of additional processes does not occur.
> If the code I have created thus far would be useful, I will post.
>
> Thank you in advance for the assistance,
> Christopher Dickerson
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