[Ipopt] AMPL options problem

[Juan Ignacio Laiglecia]

Dear,
I have had problem when I used this IPOPT option: 
ma57_pivot_order 
 
I am solving an entire natural gas plant in AMPL and I am very interested in reducing the computational times. In the ipopt option line I introduced it in this way: 
 
option ipopt_options " linear_solver ma57 ma57_pivot_order 4 ";
option solver ipopt ;
 
When I run the problem, AMPL send me: Unknown Keyword “ma57_pivot_order”
Do you know what would the problem be? I should mention that I have the ipopt3.8 version.

Thank you very much in advance.
Juan
 		 	   		  
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