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MINLPLib Changelog
==================

02/17/13:
---------
Nick Sahinidis recognized that the models nuclear14 and nuclear24,
          nuclear14a and nuclear24a, and nuclear14b and nuclear24b
          are equal, respectively. As a consequence, the nuclear24*
          models have been removed from the MINLPLib.

08/08/12:
---------
Replaced infeasible point chp_partload_p2 by chp_partload_p3 and
          infeasible points tln6_p2 and tln7_p2 by feasible ones.
          Added $offlisting to the top of all model files to
          allow for shorter listing files.

08/06/12:
---------
Nick Sahinidis recognized that the models detf1 and saa_2 are
          equal. As a consequence, model detf1 has been removed
          from the MINLPLib. The new best known solution for saa_2
          is 12.1613.

05/25/12:
---------
Updated MINLPLib statistics to correctly reflect best known value
          for water4 (907.017) as updated on 11/05/11.

02/14/12:
---------
Removed solution points chp_partload_p4.gdx and contvar_p2.gdx,
          since they were not feasible. This increases the best
          known value for contvar to 809149.8272.

01/17/12:
---------
New improved solutions for models eg_all_s (7.6578), mbtd(4.8333),
          saa_2 (12.6922), water3 (907.017), waters (913.776),
          watersym2 (940.9189), and watersbp (913.7757).
          The points have been found by SCIP.

11/09/11:
---------
New improved solutions for models saa_2 (12.7375), tls7 (15.5),
          waters (935.6923), and watersbp (947.2880). The points have
          been found by SCIP. The new solutions for waters, watersbp
          and tls7 replace the ones added on 11/05/11.

11/05/11:
---------
New improved solutions for models tls5 (10.3), tls6 (15.3), tls7 (15.8),
          nuclear25b (-1.1010), water3 (920.6722), water4 (907.017),
          watersbp (961.2847), waters (938.9031), watersym1 (913.7757)
          have been added. These points have been found by SCIP.

08/29/11:
---------
CS Norman Shiau contributed 3 new models that perform an optimal vehicle
          allocation for minimizing greenhouse gas emissions:
          ghg_1veh, ghg_2veh, ghg_3veh


08/08/11:
---------
Toni Lastusilta pointed out that for some of the fo7, mo7, and o7 instances,
          some provided points are only feasible w.r.t. very loose tolerance,
          e.g., 1e-3. As a consequence, the points fo7_p1, fo8_p1, fo9_p1,
          o7_2_p1, and o7_p1 have been removed and the points fo7_2_p1 and
          m7_p1 have been replaced by more accurate ones. Note that this
          increases the best known value for fo7_2 to 17.7493 (previously
          17.7489).


08/01/11:
---------
Toni Lastusilta contributed improved solutions for models
          nuclear14b (-1.1169), nuclear24b (-1.1169), nuclear49b (-1.1169),
          nuclearvd (-1.0344), tls12 (112.8), water3 (930.9874),
          waterful2 (1012.6093), watersym1 (941.5144), waterx (909.0401).
          The solutions were found via AlphaECP.


06/21/11:
---------
Pietro Belotti contributed an improved solution with value -115656.5
          for model cecil_13.gms. He ran Couenne/trunk for 21000 seconds,
          enumerating 2.1 million branch-and-bound nodes.


04/08/11:
---------
lop97ic.gms: A solution of value 4041.83 has been found by
          LindoGlobal. The solution is recorded in point
          lop97ic_p2.gdx.


01/11/11:
---------
Giacomo Nannicini contributed global solutions for the models water4
          and waterz. He used Couenne with strong branching and a new
          aggressive probing bound tightening technique.


09/14/09:
---------
Stefan Vigerske kindly agreed to become the next managing editor of
          MINLPWorld. Thanks to Michael Bussieck for more than eight
          years of service. Michael remains with MINLPWorld as a new 
          member of the advisory board.


09/14/09:
---------
Tapio Westerlund and Toni Lastusilta contributed four new models:
          netmod_dol1,_dol2,_kar1, and _kar2 with points.


09/14/09:
---------
Tapio Westerlund and Toni Lastusilta contributed various new points
          and pointed out some bugs in the points file. Jon Lee (IBM)
          contributed the global solution to tln12. Stefan Vigerske
          contributed the global optimum solution to lop97icx. Klaus
          Schittkowski and Thomas Lehmann reported a new solution for
          eg_all_s.

          Stefan Vigerske suggested to change the quadratic term **2
          to sqr() in model product and product2.


08/26/08:
---------
Tapio Westerlund and Toni Lastusilta contributed improved points for
          the models fo7, fo8, fo9, o7, o7_2, tln12, and waters using
          AlphaECP. SBB when restarted from the AlphaECP solution
          found an even better point for tln12 (p2). The incorrect
          point p1 for nvs14 has updated.


04/22/08:
---------
Stefan Vigerske contributed a new model chp_partload related to the 
          super* models already in the library. He also provide four 
          points found by SBB, LaGO, and OQNLP.


06/14/07:
---------
Reorganization of the point files: The ASCII point files have been
          changed into GDX files for easier use. The GAMS command
          'execute_loadpoint "m_p1.gdx"' reads the point into GAMS. A
          wrapper called loadpoint has been added to the library, so
          loading of points from the command line can be used as
          follows:

          gams batch u1=loadpoint --pfile batch_p1.gdx 
          
          In case you liked the old point format. You can use the GDX
          utility gdxdump to generate ASCII based point format:
          'gdxdump batch_p1.gdx format=gamsbas > batch.p1' and then
          run the model: 'gams batch u1=batch.p1'.

Tapio Westerlund contributed two models: csched1a and csched2a.
          These models are the corrected ones from the paper. The
          printed version of the paper had some data inconsistencies.
          The objective of the models also has been reformulated.
          Points for these models also available.

Monique Guignard contributed instances from the generalized quadratic
          assignment problem: pb302035, pb302055, pb302075, pb302095,
          pb351535, pb351555, pb351575, pb351595. AO and ECP methods
          do very well on those. Points have been given for all of
          them.

Toni Lastusilta added bounds to some existing models to avoid
          evaluation errors with using the AlphaECP solver. The new
          models are: enpro48pb, enpro56pb, ex3pb, ravempb, and
          risk2bpb. Points have been given for all of them.

New points: There were a few models without an integer solution. We
          added some solutions using various solvers: waterful2_p2,
          m7_p1, m6_p1, m3_p1, fo7_2_p1, fo7_p1, fo8_p1, fo9_p1,
          o7_2_p1, o7_p1, tls5, tls6.

          The only models in MINLPLib without an integer solution are
          nuclear104, nuclear10a, nuclear10b, and space960.

The listing of the best known solution on the model page contains now
          a comment. This might indicate that the solution is the
          global optimum solution. We give the reason why we think
          this is the global optimum. In most cases, a global solver
          like BARON provided the solution. Please note that all
          solvers work with tolerances, so globally optimal is subject
          to the solver tolerances (optimality as well as
          feasibility).

Starting with GAMS22.5 there is a new global solver called LINDOGLOBAL
          from Lindo Systems, Inc. LINDOGLOBAL accepts models with
          trigonometric functions (sin, cos, ...). With that we have
          been able to mark some more solutions to problems as
          globally optimal.

There are 103 quadratic problems among the 260 models in MINLPLib. The
          model minlplib.gms contains the set m_miqcp with these
          models. The scalar models have been adjusted so the model
          type on the solve statement can be adjusted. This is also
          useful, if one wants to solve the relaxed model. Just add
          --minlp=miqcp or --minlp=rminlp to your model line to set
          the model type in the solve statement.


01/11/07:
---------
Stefan Vigerske provided new solutions for models pump (p2) and
          eq_int_s (p1), Both solutions were found with LaGO/Conopt
          and verified using SBB and CONOPT.

01/02/06:
---------
Stefan Vigerske provided new solutions (p2) for models nuclear14b,
          nuclear24b, and nuclear25b.  Both solutions were found with
          LaGO and verified using SBB and CONOPT. 

          These points have been improved by SBB/CONOPT (p3). The
          tryint option in SBB lets one reproduce a given point by
          setting branching directions on discrete variables. The SBB
          option "dfsstay" does a couple of node explorations in the
          neigborhood of the integer solution found and find the
          "best" solution within a neighborhood. Using this approach
          all three points have been slightly improved.

12/29/05:
---------
Tapio Westerlund also provided solutions for the models added on 12/19/05. 
          All solutions were found with AlphaECP and verified using SBB 
          and CONOPT.

12/19/05:
---------
32 new models fo[7,8,9]_ar*, m7_ar*, no7_ar* o[7,8,9]_ar* added: Tapio 
          Westerlund contributed these model. They comes from the
          paper 'Castillo, I, Westerlund, J, Emetb, S, and Westerlund,
          T, Optimization of block layout design problems with unequal
          areas: A comparison of MILP and MINLP optimization methods. 
          Computers and Chemical Engineering 30 (2005), 54-769.

02/19/05:
---------
Two new GAMS Client models added: uselinear and blendgap. Furthermore,
          Stefan Vigerske contributed four model (super1,2,3,and 3t)
          together with points generated by LaGO.

11/30/04:
---------
New improved point for tls4. The solution was obtained by Nick
          Sahinidis and Mohit Tawarmalani using BARON in the paper
          "A polyhedral branch-and-cut approach to global
          optimization" to appear in Math. Prog.

10/26/04:
--------
Facility layout problems fo7_2, fo7, fo8, fo9, m3, m6, m7, o7_2, and
          o7 added. Tapio Westerlund contributed these. The original
          models are part of the AlphaECP package. These are difficult
          convex models.

New improved points for def1, dosemin3d, eniplac, fuzzy, hda and
          waterz. The solutions were obtained by AOA, the AIMMS Outer
          Approximation algorithm. The points were contributed by
          Marcel Hunting.

07/17/03:
--------
tls4.gms: A solution of value 9.30 has been found by by a novel
           simplicial-approximation based algorithm (Goyal and
           Ierapetritou). The solution is recorded in point tls4.p2.

07/02/03:
---------
mbtd.gms added: A GAMS Development client model.

prob02.gms, prob03.gms, prob10.gms added: Example models from the AlphaECP
           system by T. Westerlund and K. Lundqvist.

11/06/02:
---------
Updated URL for MacMINLP.

7/25/02:
--------
nvs01.gms-nvs24.gms added: A collection of small non-convex models from a 1985
           paper by Gupta and Ravindran. The global optimum solution is known
           for these problems. Contributed by Nick Sahinidis.

product.gms and product2.gms: Two product positioning models contributed by Aldo
           Vecchietti.

fuzzy.gms and risk2b.gms: Two GAMS Development client models.

du-opt5.gms, du-opt.gms, eg_all_s.gms eg_disc_s.gms eg_disc2_s.gms eg_int_s.gms:
           Examples from Bram Schoonen's Master Thesis 'Mixed Integer Non-linear
           Programming in Design Optimization"

For all new models feasible (for nvs* problems even global optimal) points have
been found and added to the library.

07/24/02:
---------
windfac.gms, elf.gms, sep1.gms, pump.gms: Added initial values.

10/15/01:
---------
lop97ic.gms: A solution of value 4284.59 has been found by
           SBB/CONOPT3. The solution is recorded in point
           lop97ic.p1.

08/08/01:
---------
eniplac.gms added.

06/28/01:
---------
nous1.gms N. Sahinidis reported an error in this model which caused
          the infeasibility of the model. The RHS of equation e27
          reads now 50 instead of 70. A global optimum point is also
          added to the library.

06/25/01:
---------
lop97icx.gms and lop97ic.gms added. The first one is derived from the
latter by fixing variables that were zero in the relaxed problem. A
solution of lop97icx.gms can be transfered into a solution of lop97ic.

The references for the models have been redone.

For models where the original source is available we have a link to
this source.

05/08/01:
---------
tln6.gms   The global solution of value 15.3 has been found by
           BARON. The solution is recorded in point tln6.p2. This
           updates the best know solution of value 15.6 which is
           recorded in tln6.p1

tln7.gms   The global solution of value 15.0 has been found by
           BARON. The solution is recorded in point tln7.p2. This
           updates the best know solution of value 19.5 which is
           recorded in tln7.p1

05/04/01:
---------
waste.gms: A solution of value 598.919176 has been found by
           SBB/SNOPT/CONOPT. The solution is recorded in point
           waste.p2. This updates the best know solution of value
           696.69 which is recorded in waste.p1

05/01/01:
--------- 
MINLPLib released with 136 model from 43 applications with 130 points.
126 of the models have some best known solution. For 10 models we do
not have an integer solution including 4 models for which we can't
provide a solution of the relaxation.