Thanks for the help Rob.  With the attempt to minimize number of builds based on both minimizing drivetimes and the known locations to build I came up with this.  If this looks off to you let me know but it appears to work with the following data as expected (sites 1, 2, and 3 are built with the only customer assiged to site 3 being C11).   proc optmodel; set <str, str> SITEStoDEVICES; num DriveTime {SITEStoDEVICES}; read data DTMS into SITEStoDEVICES = [destination origin] DriveTime; set CUSTOMERS = setof {<i,j> in SITEStoDEVICES} i; /*set SITES = setof {<i,j> in SITEStoDEVICES} j;*/ /*assignment variable*/ var V {SITEStoDEVICES} binary; set <str> SITES; num REQ_LOC_BY_MGMT_NUM {SITES}; read data SiteData into SITES = [site] REQ_LOC_BY_MGMT_NUM; /* build variable*/ var Build {SITES} binary; /* objective functions */ /* min TotalCost = sum {<i,j> in SITEStoDEVICES} DriveTime[i,j] * V[i,j];*/ /* min totalbuilds = sum {<deviceSiteId, techSiteId> in SITEStoDEVICES} Build[techSiteId];*/ min cost = sum {i in CUSTOMERS, j in SITES} V[i,j] * DriveTime[i,j]; min totalcost = cost + sum{j in SITES} Build[j]; /*min totalbuilds = sum {<deviceSiteId, techSiteId> in SITEStoDEVICES} Build[techSiteId]*DriveTime[deviceSiteId, techSiteId];*/ /*device assigned to only one site and every device is assigned*/ con Balance {i in CUSTOMERS}: sum {<(i),j> in SITEStoDEVICES} V[i,j] = 1; /* must build sites */ con mustbuild {techSiteId in SITES: REQ_LOC_BY_MGMT_NUM[techSiteId] = 1}: Build[techSiteId] = 1; /* must build sites with assigned locations */ con link {deviceSiteId in CUSTOMERS, techSiteId in SITES}: V[deviceSiteId,techSiteId] <= Build[techSiteId]; /* do not assign customer to site more than x units away */ con distance_at_most {i in CUSTOMERS, j in SITES: DriveTime[i,j] > 1.99}: V[i,j] = 0; /* solve;*/ solve with milp/timetype=real; create data outdata from [i j] DriveTime V Build[j] REQ_LOC_BY_MGMT_NUM[j]; run;         data SiteData; input site $ REQ_LOC_BY_MGMT_NUM; datalines; S1 0 S2 0 S3 1 S4 0 ;     data DTMS; input destination : $11. origin : $11. REQ_LOC_BY_MGMT_NUM : best8. DriveTime ; datalines; C1 S1 0 .15 C2 S1 0 .10 C3 S1 0 .11 C4 S1 0 .12 C5 S1 0 .13 C6 S1 0 2.15 C7 S1 0 2.10 C8 S1 0 2.11 C9 S1 0 2.12 C10 S1 0 2.13 C11 S1 0 1.99 C1 S2 0 2.75 C2 S2 0 2.70 C3 S2 0 2.71 C4 S2 0 2.72 C5 S2 0 2.73 C6 S2 0 .15 C7 S2 0 .10 C8 S2 0 .11 C9 S2 0 .12 C10 S2 0 .13 C11 S2 0 2.99 C1 S3 1 7.15 C2 S3 1 7.10 C3 S3 1 7.11 C4 S3 1 7.12 C5 S3 1 7.13 C6 S3 1 6.15 C7 S3 1 6.10 C8 S3 1 6.11 C9 S3 1 6.12 C10 S3 1 6.13 C11 S3 1 1.05 C1 S4 0 0.15 C2 S4 0 0.10 C3 S4 0 0.11 C4 S4 0 0.12 C5 S4 0 7.13 C6 S4 0 0.15 C7 S4 0 0.10 C8 S4 0 0.11 C9 S4 0 7.12 C10 S4 0 7.13 C11 S4 0 8.79 ; ... View more

the line   var Build {SITEStoDEVICES} binary;   should read var Build {SITES} binary;   in the example code.  My apologies for being unclear there.       ... View more

Thanks for the quick reply Rob.  I'm running into errors when trying to read the data "REQ_LOC_BY_MGMT_NUM" into the model initially.    I've placed the statement "num REQ_LOC_BY_MGMT_NUM {SITES};" both before and after the SITES node creation.  in both cases I get an error.  The first case I get the error ERROR 525-782: The symbol 'SITES' is unknown.   and in the second case (placement after the SITES node create) ERROR 525-782: The symbol 'REQ_LOC_BY_MGMT_NUM' is unknown.   Specifically an example of what I've got is here:   /* Data Example */ data DTMS; input destination : $11. origin : $11. REQ_LOC_BY_MGMT_NUM : best8. DriveTime ; datalines; C1 S1 0 .15 C2 S1 0 .10 C3 S1 0 .11 C4 S1 0 .12 C5 S1 0 .13 C1 S2 0 5.15 C2 S2 0 5.10 C3 S2 0 5.11 C4 S2 0 5.12 C5 S2 0 5.13 C1 S3 0 7.15 C2 S3 1 7.10 C3 S3 1 7.11 C4 S3 1 7.12 C5 S3 1 7.13 C6 S1 0 5.15 C7 S1 0 5.10 C8 S1 0 5.11 C9 S1 0 5.12 C10 S1 0 5.13 C6 S2 0 .15 C7 S2 0 .10 C8 S2 0 .11 C9 S2 0 .12 C10 S2 0 .13 C6 S3 1 6.15 C7 S3 1 6.10 C8 S3 1 6.11 C9 S3 1 6.12 C10 S3 1 6.13 ; 　 proc optmodel; set <str, str> SITEStoDEVICES; num DriveTime {SITEStoDEVICES}; read data DTMS into SITEStoDEVICES = [destination origin] DriveTime REQ_LOC_BY_MGMT_NUM; set CUSTOMERS = setof {<i,j> in SITEStoDEVICES} i; set SITES = setof {<i,j> in SITEStoDEVICES} j; num REQ_LOC_BY_MGMT_NUM {SITES}; /*assignment variable*/ var V {SITEStoDEVICES} binary; var Build {SITEStoDEVICES} binary; /* objective functions */ min TotalCost = sum {<i,j> in SITEStoDEVICES} DriveTime[i,j] * V[i,j]; min totalbuilds = sum {<deviceSiteId, techSiteId> in SITEStoDEVICES} Build[techSiteId];   /*device assigned to only one site*/ con Balance {i in CUSTOMERS}: sum {<(i),j> in SITEStoDEVICES} V[i,j] = 1; /* must build sites with assigned locations */ con link {deviceSiteId in CUSTOMERS, techSiteId in SITES}: V[deviceSiteId,techSiteId] <= Build[techSiteId]; /*must build certain sites*/ con mustbuild {techSiteId in SITES: REQ_LOC_BY_MGMT_NUM[techSiteId] = 1}: Build[techSiteId] = 1; /*for {techSiteId in SITES: REQ_LOC_BY_MGMT_NUM[techSiteId] = 1}*/ /* fix Build[techSiteId] = 1;*/ solve; /* print V;*/ create data outdata from [i j] DriveTime V Build REQ_LOC_BY_MGMT_NUM; run;   ... View more

Good Day Rob,   As a follow up to this question I am now attempting to place a constraint on the model in which certain sites are known to be built for this facility location problem.  In short, we know from a business persepective specific locations must be built and want the remaining locations to be greefield solutioned.   Here's what I've got.   Variable in my data frame "REQ_LOC_BY_MGMT_NUM" has 1's where the site is a known location to build and 0's otherwise.   I've tried the following: added to the preamble of the code num REQ_LOC_BY_MGMT_NUM {SITEStoDEVICES};   added to the objective function statements min TotalDriveTime = sum {<customerName, siteName> in SITEStoDEVICES} DriveTimeMin[customerName, siteName] * V[customerName, siteName]; min totalbuilds = sum {<deviceSiteId, techSiteId> in SITEStoDEVICES} Build[techSiteId];   and new constraint /* must build specific sites */ con mustbuild {deviceSiteId in CUSTOMERS, techSiteId in SITES}: REQ_LOC_BY_MGMT_NUM[deviceSiteId,techSiteId] <= Build[techSiteId];     it's throwing the error: ERROR: The array subscript 'V['xxxxxxxxxxxxx','xxxxxxxxxxxxxxxxx']' is invalid at line 53 column 7.   Thoughts on how to make this work?  It's probably me just not understainding the example from here:  http://go.documentation.sas.com/?docsetId=ormpug&docsetTarget=ormpug_optmodel_examples07.htm&docsetVersion=14.2&locale=en   Thanks again! ... View more

good to know. I'll play around with it now that I've seen a working example and should be able to self serve for the needed finale! ... View more

wow that was quick.  Thank you @RobPratt; much appreciated.  The solution worked for my simple case and I'm figuring it'll do for the full scope case.   i see where you're going with the straight up minimum selection for this simple situation.  however, i needed to know how to make the optimization portion work for the second phase of the project which is coming up.   the issue i ran into with the referenced example is this portion of the code /* distance from customer i to site j */ num dist {i in CUSTOMERS, j in SITES} = sqrt((x[i] - x[j])^2 + (y[i] - y[j])^2); read data cdata into CUSTOMERS=[name] x y demand; read data sdata into SITES=[name] x y fixed_charge; specifically I ran into was the fact that my data is vertically strutured with all the customer/site combos with their associated drive times.  The example assumed two data sets, one for customers and one for sites with both having x/y coordinants and the "cost" is distance which is calculable using the euclidian metric; I was able to easily enough chage that to use lat/longs and geo distances but distances doen't equate to drive times.   I wasn't sure how to modify the code to do a "group by" sort of thing with a single data frame.   I could easily enough get the data into three frames where I had customers, sites, and then drive times in a third frame but wasn't sure how to get the dist variable from the third frame by looking up the customer / site combo; and unfortunantly the drive times is not a calculable metric given the lat/longs of my customers/sites.   I would love to see how you'd modify the referenced code to do either 1) a look up for the dist variable from a third data frame and/or 2) use a single data frame with customer/site combos and a seperate third column with the "dist" or cost variable.   being so new SAS for these types of problems has really been fun but challenging.  Your help has been infinately valuable and I thank you again!     ... View more

hey @RobPratt, I am struggling with a simple modification to the above code.  I'm really really new to SAS so please do forgive me if this is something very simple -- also new to the forum;  I've looked all over the web and this example is the closest I've found where the data is in the format which I've got and the problem statement is similar.   In my case I have different constraints:  i have destinations(n=15Kish) and origins(100ish)  (i=destinations and j=origins) and must have every i assigned to only one j (that is each customer is assigned to only one distribution site).  The costs are drive times from the distribution hub to the customer and the objective is to minimize the drive times -- in short it's basically assigning a customer to it's associated site with the shortest drive time.  heres the mod i attempted which isn't working for me; sas tells me that the solution is "infeasible" which seems a bit odd to me.  in the simple case of 10 destinations and 3 distribution sites i also get the "infeasible" issue so I'm thinking it's my constraint line which is off.   specifically I used the following constraint code: /*device assigned to only one site*/   con Balance {i in NODES}:       sum {<(i),j> in SITEStoDEVICES} V[i,j] = 1;   which is a modification of the constraints from the OP.    Without the constraint I get all V's as zero -- I think thats meaning no assignemnts are made which of course minimized drive time to be zero overall.  However, I set this up to ensure C1-C5 are assigned to S1 while C6-C10 are assigned to S2 with non assigned to S3.   Please help!  I'm just not understanding something simple here.   in short the overall project objective that I'm trying to achieve is 1) assign customers to the associated sites with lowest drive times 2) get the all customers outside of a specified drive time 3) take the group from (2) and determine  where would be the best new sites to have as distribution hubs to ensure all customers are within the specified drive time.   next phase would be to optimize on lowest number of distro hubs such that all customers are within a certain drive time but thats outsie the scope of my imediate need.   below is the example data/code.   data DTMS; input destination  : $11. origin : $11. DriveTime; datalines; C1 S1 .15 C2 S1 .10 C3 S1 .11 C4 S1 .12 C5 S1 .13 C1 S2 5.15 C2 S2 5.10 C3 S2 5.11 C4 S2 5.12 C5 S2 5.13 C1 S2 7.15 C2 S3 7.10 C3 S3 7.11 C4 S3 7.12 C5 S3 7.13 C6  S1 5.15 C7  S1 5.10 C8  S1 5.11 C9  S1 5.12 C10 S1 5.13 C6  S2 .15 C7  S2 .10 C8  S2 .11 C9  S2 .12 C10 S2 .13 C6  S3 6.15 C7  S3 6.10 C8  S3 6.11 C9  S3 6.12 C10 S3 6.13 ; proc optmodel; set <str, str> SITEStoDEVICES; num DriveTime {SITEStoDEVICES}; read data DTMS into SITEStoDEVICES = [destination origin] DriveTime; set NODES = union {<i,j> in SITEStoDEVICES} {i,j}; /*assignment variable*/ var V {SITEStoDEVICES} binary; /*objective function*/    min TotalCost = sum {<i,j> in SITEStoDEVICES} DriveTime[i,j] * V[i,j];   /*device assigned to only one site*/   con Balance {i in NODES}:       sum {<(i),j> in SITEStoDEVICES} V[i,j] = 1;     solve; /*   print V;*/    create data outdata from [i j] DriveTime V; run;         ... View more