Dear Experts,

I solved my model with cplex solver with objective function equal 109. Then I tried to solve the model with xpress solver, the xpress gave me an objective function equal 111 and it says “fixed LP solved successfully, objective = 111.”. of course its not optimal because Cplex found the smaller amount. Maybe the reason is that xpress solver says that it “Will try to keep branch and bound tree memory usage below 1.2Gb” in my system, so my question is how to increase the memory usage for xpress solver?

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Tino,

By default, GAMS runs MIP models with a relative optimality gap of 10%, i.e. optcr = 0.1. You don’t mention if or how you reset this, so I’d start by looking at that, not memory issues for XPRESS.

-Steve

On Sun, May 17, 2015 at 6:15 AM, Tino wrote:

Dear Experts,

I solved my model with cplex solver with objective function equal 109. Then I tried to solve the model with xpress solver, the xpress gave me an objective function equal 111 and it says “fixed LP solved successfully, objective = 111.”. of course its not optimal because Cplex found the smaller amount. Maybe the reason is that xpress solver says that it “Will try to keep branch and bound tree memory usage below 1.2Gb” in my system, so my question is how to increase the memory usage for xpress solver?

Steven Dirkse, Ph.D.

GAMS Development Corp., Washington DC

Voice: (202)342-0180 Fax: (202)342-0181

sdirkse@gams.com

http://www.gams.com

thank you Steven

On Monday, May 18, 2015 at 7:21:50 PM UTC+3, Steven Dirkse wrote:

Tino,

By default, GAMS runs MIP models with a relative optimality gap of 10%, i.e. optcr = 0.1. You don’t mention if or how you reset this, so I’d start by looking at that, not memory issues for XPRESS.

-Steve

On Sun, May 17, 2015 at 6:15 AM, Tino wrote:

Dear Experts,

I solved my model with cplex solver with objective function equal 109. Then I tried to solve the model with xpress solver, the xpress gave me an objective function equal 111 and it says “fixed LP solved successfully, objective = 111.”. of course its not optimal because Cplex found the smaller amount. Maybe the reason is that xpress solver says that it “Will try to keep branch and bound tree memory usage below 1.2Gb” in my system, so my question is how to increase the memory usage for xpress solver?

Steven Dirkse, Ph.D.

GAMS Development Corp., Washington DC

Voice: (202)342-0180 Fax: (202)342-0181

sdi...@gams.com

http://www.gams.com

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