Make some enumint options more informative in the option definition file

Author: 0x17

assets/optcuopt.def

@@ -4,8 +4,8 @@
 num_cpu_threads integer 0 -1 -1 maxint 1 1 Controls the number of CPU threads used in the LP and MIP solvers (default GAMS Threads)
 num_gpus integer 0 1 1 2 1 2 Controls the number of GPUs to use for the solve. This setting is only relevant for LP problems that uses concurrent mode and supports up to 2 GPUs at the moment. Using this mode will run PDLP and barrier in parallel on different GPUs to avoid sharing single GPU resources.
 presolve enumint 0 -1 1 1 Modify chosen presolve procedure
- -1 1 default
-  0 1 off
+ -1 1 default (Papilo for MIP, PSLP for LP)
+  0 1 off (disable presolve)
   1 1 papilo
   2 1 pslp
 dual_postsolve boolean 0 0 1 2 Controls whether dual postsolve is enabled. Disabling dual postsolve can improve solve time at the expense of not having access to the dual solution. Enabled by default for LP when presolve is enabled. This is not relevant for MIP problems
@@ -14,14 +14,14 @@ prob_read string 1 "" 1 1 Reads a problem from an MPS file
 pdlp_solver_mode enumint 0 4 1 2 Controls the mode under which PDLP should operate
  0 1 stable1
  1 1 stable2
- 2 1 methodical1
- 3 1 fast1
- 4 1 stable3
+ 2 1 methodical1 Takes slower individual steps, but fewer are needed to converge.
+ 3 1 fast1 Fastest mode, but with less success in convergence.
+ 4 1 stable3 Best overall mode from experiments; balances speed and convergence success. If you want to use the legacy version, use Stable1. (default)
 method enumint 0 0 1 2 Controls the method to solve the linear programming problem
- 0 1 concurrent
- 1 1 pdlp
- 2 1 dual_simplex
- 3 1 method_barrier
+ 0 1 concurrent Use PDLP, dual simplex, and barrier in parallel (default).
+ 1 1 pdlp Use the PDLP method.
+ 2 1 dual_simplex Use the dual simplex method.
+ 3 1 method_barrier Use the barrier (interior-point) method.
 iteration_limit integer 0 maxint 0 maxint 1 2 Controls the iteration limit after which the solver will stop and return the current solution (default GAMS IterLim)
 infeasibility_detection boolean 0 0 1 2 Controls whether PDLP should detect infeasibility   
 strict_infeasibility boolean 0 0 1 2 Controls the strict infeasibility mode in PDLP