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FICO's avatar
FICO
Community Manager
6 years ago

xpress.InterfaceError: Incorrect control name error

I upgraded FICO Xpress Optimization from version 8.8.0 to 8.9.3. The following used to work in the python3 interface of version 8.8.0: import xpress as xp xp.controls.outputlog = 0 # disable all s...
fico® xpress
FICO's avatar
FICO
Community Manager
6 years ago

Hi Chris, it seems you are correct. I'm indeed using an OEM license with linux, and the XPRESS environment variable points to the OEM license file. 

import xpress as xp
oemnum = hidden
string= ""
n,string = xp.license(0,string)
lic = oemnum - n*n//19
n,string = xp.license(lic,string)
 
xp.controls.outputlog = 0
 
S = range(5)          # that's the set {0,1,2,3,4}
value = [102, 512, 218, 332, 41]  # or just read them from file
weight = [21, 98, 44, 59, 9]
 
x = [xp.var(vartype=xp.binary) for i in S]
profit = xp.Sum(value[i] * x[i] for i in S)
 
p = xp.problem("knapsack")
p.addVariable(x)
p.addConstraint(xp.Sum(weight[i] * x[i] for i in S) <= 130)
p.setObjective(profit, sense=xp.maximize)
 
p.solve()

The code snippet above didn't work and produced the aforementioned error. However, replacing lines 3-6 with:

if (xp.beginlicensing()):
    string = ""
    n,string = xp.license(0,string)
    lic = oemnum - n*n//19
    n,string = xp.license(lic,string)
    xp.init()
    xp.endlicensing()

solved the problem.

Also note that, the first code block works fine if line 8 is commented out. This is very confusing and should probably throw a more descriptive error than 'xpress.InterfaceError: Incorrect control name', i.e. some error that points to the licensing issue.

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