Optimization Settings - Revision history

Jonare at 10:38, 25 August 2023

2023-08-25T10:38:21Z

Peder at 09:41, 18 June 2010

2010-06-18T09:41:53Z

Hah at 10:56, 21 January 2010

2010-01-21T10:56:24Z

Hah at 10:54, 21 January 2010

2010-01-21T10:54:20Z

Peder at 11:24, 20 January 2010

2010-01-20T11:24:41Z

Peder at 11:21, 20 January 2010

2010-01-20T11:21:40Z

Peder at 11:20, 20 January 2010

2010-01-20T11:20:09Z

Peder at 11:19, 20 January 2010

2010-01-20T11:19:34Z

Peder at 11:16, 20 January 2010

2010-01-20T11:16:23Z

Hah at 15:12, 26 September 2009

2009-09-26T15:12:23Z

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 ** Time limit: The maximum time for the solving a problem. If the time limit has been passed but an optimal solutions has not been found, the best solution found is returned. For difficult problems it is possible that no feasible solution is found.
 ** Round to integer: If check, decision variables are rounded to the nearest 0/1 integer value.
 *'''The SCIP/SoPlex Settings-tab''': Here you select the [[Optimization#Solvers | SCIp/SoPlex]] binary file (.exe) that you must have on your disk, see [[Optimization#Solvers]].

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 ** Round to integer: If check, decision variables are rounded to the nearest 0/1 integer value.
-*'''The Lpsolve Settings-tab''' allows the user to select default settings in presolving.
+*'''The Cplex Settings-tab''' shows whether you have av valid licence file.
-*'''The Cplex Settings-tab''' allows the user to set and test the validity of the licence file.
+*'''The SCIP/SoPlex Settings-tab''': Here you select the [[Optimization#Solvers | SCIp/SoPlex]] binary file (.exe) that you must have on your disk, see [[Optimization#Solvers]].

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 ** Relative mip gap: Relative optimization tolerance. The optimization algorithm stops when an integer solution is quaranteed to be within this percentage of the true optimal solution.
 ** Absolute mip gap: Absolute optimization tolerance (not available in Lp_Solve). The optimization algorithm stops when an integer solution is proven to be within this absolute difference of the optimal solution.
-** Time limit: The maximum time for the solving a problem. If the time limit has been passed but an optimal solutions has not been found, the best solution found is returned. For difficult problems it is possible that no feasible solutions is found.
+** Time limit: The maximum time for the solving a problem. If the time limit has been passed but an optimal solutions has not been found, the best solution found is returned. For difficult problems it is possible that no feasible solution is found.
 ** Round to integer: If check, decision variables are rounded to the nearest 0/1 integer value.
 *'''The Lpsolve Settings-tab''' allows the user to select default settings in presolving.
 *'''The Cplex Settings-tab''' allows the user to set and test the validity of the licence file.

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-Applying a LP-optimization model in forest management planning, integer solutions are sometimes of interest. A stand is usually regarded as a treatment unit to be completely treated according to a certain treatment in a certain period. This might be of certain interest when it comes to short term-planning, i.e. what to do now and in the next year - couple of years.
+Applying a LP-optimization model in forest management planning, integer solutions are sometimes of interest. A stand is usually regarded as a treatment unit to be completely treated according to a certain treatment in a certain period. This might be of special interest when it comes to short term-planning, i.e. what to do now and in the next year - couple of years.
 The most straightforward way to obtain integer solutions is to allow only integer values of the decision variable, i.e. constrain the range type of ''x<sub>i, j</sub>'' to "Binary". However, this might lead to infeasible solutions. Another way is to round off to closest integer value (0 or 1), hence forcing the results to be a set of complete treatment programmes for each stand in the analysis area. In menu "Optimization" > "Settings...":
-*'''The General-tab''' allows the user to, e.g., selecting "Round to integer solution". Do observe that this is done after solving the optimization problem. Any results shown in the output window will not be rounded off (except the decision variable, with its actual values within parentheses). Results derived from the result database will however be of integer solutions, if this was selected. Optimization results are saved to the database by pressing the "Save"-button in the optimization model builder-window. As an alternative to rounding off, the "Mip Gap" gives an opportunity to accept a solution not certainly optimal. A relative gap of 1% imply that the solution might be one percentage from the optimum. An absolute gap in defined in the same unit as the objective function. The "Time Limit" defines the time, in seconds, for the optimization model to search for a feasible solution.
+*'''The General-tab''' allows the user to, e.g., selecting "Round to integer solution". Do observe that this is done after solving the optimization problem. Any results shown in the output window will not be rounded off (except the decision variable, with its actual value within parentheses). Results derived from the result database will however be of integer solutions, if this was selected. Optimization results are saved to the database by pressing the "Save"-button in the optimization model builder-window. As an alternative to rounding off, the "Mip Gap" gives an opportunity to accept a solution not certainly optimal. A relative gap of 1% imply that the solution might be one percentage from the optimum. An absolute gap is defined in the same unit as the objective function. The "Time Limit" defines the time, in seconds, for the optimization model to search for a feasible solution.
 ** Relative mip gap: Relative optimization tolerance. The optimization algorithm stops when an integer solution is quaranteed to be within this percentage of the true optimal solution.
 ** Absolute mip gap: Absolute optimization tolerance (not available in Lp_Solve). The optimization algorithm stops when an integer solution is proven to be within this absolute difference of the optimal solution.

@@ Line 7: / Line 7: @@
 ** Absolute mip gap: Absolute optimization tolerance (not available in Lp_Solve). The optimization algorithm stops when an integer solution is proven to be within this absolute difference of the optimal solution.
 ** Time limit: The maximum time for the solving a problem. If the time limit has been passed but an optimal solutions has not been found, the best solution found is returned. For difficult problems it is possible that no feasible solutions is found.
 *'''The Lpsolve Settings-tab''' allows the user to select default settings in presolving.
 *'''The Cplex Settings-tab''' allows the user to set and test the validity of the licence file.

← Older revision		Revision as of 11:20, 20 January 2010
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	#'''The Lpsolve Settings-tab''' allows the user to select default settings in presolving.		#'''The Lpsolve Settings-tab''' allows the user to select default settings in presolving.
	#'''The Cplex Settings-tab''' allows the user to set and test the validity of the licence file.		#'''The Cplex Settings-tab''' allows the user to set and test the validity of the licence file.
−
−
−	*'''Note'''
−	:Values, in SEK/ha, can obviously be less than zero (negative) for stands and analysis areas in one or several periods. Make sure that this variable has a "RangeType" set to "All" (and not "Default" that only allows for positive values).

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 #'''The General-tab''' allows the user to, e.g., selecting "Round to integer solution". Do observe that this is done after solving the optimization problem. Any results shown in the output window will not be rounded off (except the decision variable, with its actual values within parentheses). Results derived from the result database will however be of integer solutions, if this was selected. Optimization results are saved to the database by pressing the "Save"-button in the optimization model builder-window. As an alternative to rounding off, the "Mip Gap" gives an opportunity to accept a solution not certainly optimal. A relative gap of 1% imply that the solution might be one percentage from the optimum. An absolute gap in defined in the same unit as the objective function. The "Time Limit" defines the time, in seconds, for the optimization model to search for a feasible solution.
-## Relative mip gap: Relative optimization tolerance. The optimization algorithm stops when an integer solution is quaranteed to be within this percentage of the true optimal solution.
+** Relative mip gap: Relative optimization tolerance. The optimization algorithm stops when an integer solution is quaranteed to be within this percentage of the true optimal solution.
-## Absolute mip gap: Absolute optimization tolerance (not available in Lp_Solve). The optimization algorithm stops when an integer solution is proven to be within this absolute difference of the optimal solution.
+** Absolute mip gap: Absolute optimization tolerance (not available in Lp_Solve). The optimization algorithm stops when an integer solution is proven to be within this absolute difference of the optimal solution.
 #'''The Lpsolve Settings-tab''' allows the user to select default settings in presolving.
 #'''The Cplex Settings-tab''' allows the user to set and test the validity of the licence file.
 *'''Note'''
 :Values, in SEK/ha, can obviously be less than zero (negative) for stands and analysis areas in one or several periods. Make sure that this variable has a "RangeType" set to "All" (and not "Default" that only allows for positive values).