A
Alec Erskine
I am delighted to see that Microsoft have made an important development in
Excel 2007 with their optimiser. You have effectively introduced a
combinatorial optimiser in Excel 2007 which was not available in Excel 2003.
This allows us to solve the “Knapsack problem†in Excel. The Knapsack
problem, sometimes called the Capital Investment problem is as follows.
Suppose we have a list of schemes, each with defined cost and defined
benefit, and we have a budget ceiling. Which schemes should we do to
maximise the total benefit, while keeping the total cost under budget? The
Excel version appears to use the fairly robust method of a standard linear
simplex optimiser combined with a branch-and-bound searcher. Can you
confirm?
An example involving 70 schemes with randomised C and B is easy to create.
There seems to be a small starting position effect in that you seem to have
to run the optimiser twice from 0’s to get it to work properly, it only gets
the “right†answer – or what I hope is the right answer on the second attempt.
I would have assumed that this optimser is independent of starting position
and am quite worried that it claims to have optimised when it has not. This
is a bug, really. Any thoughts as to why it is finishing at the wrong answer?
I cannot find any email addresses on your site to send this to and am being
warned not to send contact information. So I guess that's it then.
----------------
This post is a suggestion for Microsoft, and Microsoft responds to the
suggestions with the most votes. To vote for this suggestion, click the "I
Agree" button in the message pane. If you do not see the button, follow this
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click "I Agree" in the message pane.
http://www.microsoft.com/office/com...4-2fe17d84f7fe&dg=microsoft.public.excel.misc
Excel 2007 with their optimiser. You have effectively introduced a
combinatorial optimiser in Excel 2007 which was not available in Excel 2003.
This allows us to solve the “Knapsack problem†in Excel. The Knapsack
problem, sometimes called the Capital Investment problem is as follows.
Suppose we have a list of schemes, each with defined cost and defined
benefit, and we have a budget ceiling. Which schemes should we do to
maximise the total benefit, while keeping the total cost under budget? The
Excel version appears to use the fairly robust method of a standard linear
simplex optimiser combined with a branch-and-bound searcher. Can you
confirm?
An example involving 70 schemes with randomised C and B is easy to create.
There seems to be a small starting position effect in that you seem to have
to run the optimiser twice from 0’s to get it to work properly, it only gets
the “right†answer – or what I hope is the right answer on the second attempt.
I would have assumed that this optimser is independent of starting position
and am quite worried that it claims to have optimised when it has not. This
is a bug, really. Any thoughts as to why it is finishing at the wrong answer?
I cannot find any email addresses on your site to send this to and am being
warned not to send contact information. So I guess that's it then.
----------------
This post is a suggestion for Microsoft, and Microsoft responds to the
suggestions with the most votes. To vote for this suggestion, click the "I
Agree" button in the message pane. If you do not see the button, follow this
link to open the suggestion in the Microsoft Web-based Newsreader and then
click "I Agree" in the message pane.
http://www.microsoft.com/office/com...4-2fe17d84f7fe&dg=microsoft.public.excel.misc