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Re: [Help-glpk] Use of LP for experimental trials


From: Brady Hunsaker
Subject: Re: [Help-glpk] Use of LP for experimental trials
Date: Thu, 20 Apr 2006 16:46:08 -0400
User-agent: Mail/News 1.5 (X11/20060228)

address@hidden wrote:
Hi,

I'd like to know if I can use glpk to solve a problem where the solver in glpk would call a function. I'm an engineer who no longer does any real coding. I used simplex methods years back with good success on several types of problems. I'm working to determine the best set of test conditions for a semiconductor chip. These correspond to internal voltage levels and delays. They are set as bits. There are a total of 55 bits, in 20 variables for 3E16 combinations. I'd like to try a simplex type algo that runs a point or trial in X dimensional space, evaluates the results and selects the vectors for the next trial. Each trial takes 5 minutes.

As Andrew points out, this can't be modeled as an LP/MIP. I would recommend that you consider a local search approach, which is basically what you are outlining below. There is open-source software to do Tabu Search in Java called Open Tabu Search, available at COIN-OR (www.coin-or.org). That's one option for you.

Other questions along this line might be best directed to the sci.op-research newsgroup.

Brady


So the problem is:

1) Must be evaluated as an external function with the values passed in. The return is a value to be minimized. In other words, there are no constraints or known equation for the function.

2) Should be efficient in trials, due to the 5 min per iteration (thus my interest in Simplex over a genetic code)

3) I have to be able to convert it to integer points

4) Each variable has upper and lower limits expressed as 0-7 or 0-15.

5) The space has local minima, so if it can bounce out great. However, I am just looking for improvement over the current "optimum" not a global solution.

6) I don't need to evaluate the whole space at once, I can fix X variables and look for improvements in the settings of 20-X variables.

7) A PERL shell would set up the seed and track outputs. The glpk would be called and in turn call the function which is really a chip tester.

8) The current method employed is full matrix search on 1-3 variables at a time.

Can glpk work for this problem? If so which modules should I try and what mods to the code do I need if any? Is there other software out there better suited to this application?

Thanks in advance,

Dan





------------------------------------------------------------------------

Hi,
I'd like to know if I can use glpk to solve a problem where the solver in glpk would call a function. I'm an engineer who no longer does any real coding. I used simplex methods years back with good success on several types of problems. I'm working to determine the best set of test conditions for a semiconductor chip. These correspond to internal voltage levels and delays. They are set as bits. There are a total of 55 bits, in 20 variables for 3E16 combinations. I'd like to try a simplex type algo that runs a point or trial in X dimensional space, evaluates the results and selects the vectors for the next trial. Each trial takes 5 minutes. So the problem is: 1) Must be evaluated as an external function with the values passed in. The return is a value to be minimized. In other words, there are no constraints or known equation for the function. 2) Should be efficient in trials, due to the 5 min per iteration (thus my interest in Simplex over a genetic code)
3) I have to be able to convert it to integer points
4) Each variable has upper and lower limits expressed as 0-7 or 0-15.
5) The space has local minima, so if it can bounce out great. However, I am just looking for improvement over the current "optimum" not a global solution. 6) I don't need to evaluate the whole space at once, I can fix X variables and look for improvements in the settings of 20-X variables. 7) A PERL shell would set up the seed and track outputs. The glpk would be called and in turn call the function which is really a chip tester. 8) The current method employed is full matrix search on 1-3 variables at a time. Can glpk work for this problem? If so which modules should I try and what mods to the code do I need if any? Is there other software out there better suited to this application?

Thanks in advance,
Dan


------------------------------------------------------------------------

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--
Brady Hunsaker
Assistant Professor
Industrial Engineering
University of Pittsburgh
http://www.engr.pitt.edu/hunsaker/




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