topic Data Rate holes in Mathematical Optimization, Discrete-Event Simulation, and OR

Data Rate holes

Santha — Mon, 06 Dec 2021 17:12:41 GMT

I have four nodes. Call it p,t,c, and d. Products flow from p (that is the actual origin) and go to d (actual destination). The input data is in terms of quantities from p to d (origin to destination). However, there are carriers (c) and transits (t). The quantity from a given p to given d can flow from any combination of c and d. Each combination of p,t,c,d has its own rates. Model is set to solve the optimal cost.

SAS modeling works just fine. However, I have problem with my data that i am trying to see if we can have ideas with SAS to resolve.

For example, for p1 to d1, lets say there are 5 carriers and 4transits. so there are 20 combination possible. however, i do not have a real rate for all the 20 combinations. Reason is that not all carries operate via all ports. As a result there are some holes. I tried to fill in those holes by giving those holes a big number (max rate of that p-d pair). That works fine when i do not have many constraints. But when i do have constraints like this c can handle only x quantities (capacity constraints for a carrier), then the model picks a combination that is a fake rate meaning the big number that i artificially tried to fill in. SAS is perfectly fine that it results in infeasibility. But I was just looking for ideas to see if there is anything that you guys encountered similar to this and/or to prevent this.

Re: Data Rate holes

ballardw — Mon, 06 Dec 2021 17:48:33 GMT

Did you try including a missing values for the input data instead of a "large value" for c*t combinations that don't actually occur?

You might also want to post your code so someone with more familiarity than I have can see the options you are using. That would eliminate suggestions of what you have tried that might appear.

Re: Data Rate holes

Santha — Tue, 07 Dec 2021 14:13:27 GMT

proc optmodel;

set <str> P;
set <str> D; 
set <str> C; 
set <str> T;

read data STDOPT.PN3510_P into P=[PortSource];
read data STDOPT.PN3510_D into D=[RateMatchDest];
read data STDOPT.PN3510_L into L=[LSP];
read data STDOPT.PN3510_T into T=[Transit];

num Containers {P,D} init 0;
read data STDOPT.Data into [PortSource RateMatchDest] Containers=FEU;


num InboundLinehaul {P,T,C,D}; 
read data STDOPT.RATES into [PortSource Transit LSP RateMatchDest] InboundLinehaul=Rate;

Re: Data Rate holes

Santha — Tue, 07 Dec 2021 14:14:09 GMT

thank you for your reply. i tried that earlier but did not help. I have posted my code above.

Re: Data Rate holes

RobPratt — Tue, 07 Dec 2021 15:53:07 GMT

You can use sparse index sets of tuples as follows:

set <str,str> PD;
num Containers {PD} init 0;
read data STDOPT.Data into PD=[PortSource RateMatchDest] Containers=FEU;

set <str,str,str,str> PTCD;
num InboundLinehaul {PTCD}; 
read data STDOPT.RATES into PTCD=[PortSource Transit LSP RateMatchDest] InboundLinehaul=Rate;

Please see SAS Help Center: Sparse Modeling for another example.

Re: Data Rate holes

Santha — Wed, 08 Dec 2021 13:06:07 GMT

Rob

Thank you. that makes sense.

Is there a way where I can tell SAS when we do the READ DATA step to omit/ignore the values where we have a null or 0 values in the rates? This question I am asking when we declare num InboundLinehaul {Ports,Transit,LSP,DC}; ie. 4 individual sets?

Re: Data Rate holes

RobPratt — Wed, 08 Dec 2021 15:04:00 GMT

You can use a WHERE clause in the READ DATA statement:

read data STDOPT.RATES(where=(Rate ne 0)) into [PortSource Transit LSP RateMatchDest] InboundLinehaul=Rate;

Re: Data Rate holes

Santha — Thu, 09 Dec 2021 02:12:41 GMT

oh thank you very much