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FICO's avatar
FICO
Community Manager
1 year ago

Issue building a nonlinear expressions with Xpress python package

Hello, I was building a nonlinear expression but came across a strange behavior. I am trying to produce (1 / (a + b) ) but all that I am getting is (1 / a + b ). Below is a minimal example that s...
fico® xpress
FICO's avatar
FICO
Community Manager
1 year ago

Thanks for reporting this! This seems to be a bug in printing expressions in Python :-(

The bug is only in printing expressions in Python. If I add these lines to your code:

  p.addConstraint(f == 1)
  p.addConstraint(g == 1)
  p.write('nonlinear.lp')

then the generated nonlinear.lp file contains these lines, which look correct:

R1: { 1 / ( lambda(A) + lambda(B) ) } = 1 
R2: { ( 10 * lambda(A) + 10 * lambda(B) ) / lambda(C) } = 1

I will file an internal defect to get this fixed.

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