Re: [Help-glpk] Problems with Connecting GLPK to Excel

[glpk xypron]

Hello Aly,

> In AMPL, there is some kind of a "cross" statement that might solve that,
> but I don't know a corresponding one in GLPK, and how to use it if it
> exists!

See glpk-4.44\doc\gmpl.pdf chapter 3.4 Set expressions

> In Access, there is a table called Channels, that contains three fields,
> one called Channel ID, another for origin facilities and a third for the
> corresponding destination facilities for all pairs that have flow between
> them. 
> 
> Then, there is a table called ChannelsProducts that has a field for
> Channel ID, another for products, a third for transportation cost (from which
> t_ijp should be read), and a fourth for the flow variable values (which is the
> one x_ijp needs to be written back in).
> 
> The question is: how can I read t_ijp from and write x_ijp to this table?
> As you see there are only two fields for the indices (channel and product),
> while t_ijp and x_ijp have three indices (origin facility, destination
> facility, and product).

You don't need operator "cross", you can use the following SQL
statements

SELECT a.orig, a.dest, b.prod, b.cost 
FROM Channels a, ChannelProducts b 
WHERE a.id = b.id;

UPDATE Channels a, ChannelProducts b SET b.flow = ? 
WHERE a.id = b.id AND a.orig = "?" AND a.dest="?" AND b.prod="?"

Best regards

Xypron



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