public static LPModel RunGomory(LPModelDto dto)
{
Func <LPModel, IEnumerable <Equation> > findEquationsWithFractionConstant = (lm) => lm.Constraints.Where(
dictionaryRow => IsDecisionVariable(dictionaryRow.LeftSide.Single().Variable.Value, lm) &&
!(dictionaryRow.RightSide.SingleOrDefault(term => term.Constant)?.SignedCoefficient.Integer ?? true) // if no contstant term can be found it is equivalent with the zero constant
);
LPModel lpModel;
IEnumerable <Equation> equationsWithFractionConstant;
//IList<Equation> gomoryConstraints = new List<Equation>();
lpModel = dto.MapTo(new LPModel());
lpModel.TwoPhaseSimplex();
// constraints are in dictionary form here... we need those rows where the contstant is not an integer
equationsWithFractionConstant = findEquationsWithFractionConstant(lpModel);
#region Changing aim to minimize
lpModel.ChangeOptimizationAimTo(OptimizationAim.Minimize);
#endregion
while (equationsWithFractionConstant.Any())
{
// its form like (dictionary row): <basis variable> = <constant> +/- <coefficient><non-basis variable> +/- ... +/- <coefficient><non-basis variable>
var eqWithFracConst = equationsWithFractionConstant.First();
var varForGomory = new Variable {
Name = lpModel.DecisionVariableName.ToString(), Index = lpModel.AllVariables.Max(var => var.Index) + 1
};
var gomoryConstraint = MakeGomoryConstraint(eqWithFracConst);
gomoryConstraint.Add(gomoryConstraint.LeftSide.Copy().Multiply(-1));
gomoryConstraint.LeftSide.Add(new Term {
SignedCoefficient = 1,
Variable = varForGomory
});
gomoryConstraint.SideConnection = SideConnection.Equal;
lpModel.Constraints.Add(gomoryConstraint);
lpModel.AllVariables.Add(varForGomory);
lpModel.InterpretationRanges.Add(varForGomory.GreaterOrEqualThanZeroRange());
lpModel.DualSimplex();
equationsWithFractionConstant = findEquationsWithFractionConstant(lpModel);
/*lpModel = dto.MapTo(new LPModel());
* gomoryConstraints.ForAll(constraint =>
* {
* lpModel.Constraints.Add(constraint.Copy());
* var newVariablesFromGomoryConstraint = constraint.LeftSide.Select(term => term.Variable).Where(variable => !lpModel.AllVariables.Contains(variable.Value));
* newVariablesFromGomoryConstraint.ForAll(variable =>
* {
* lpModel.AllVariables.Add(variable.Value);
* lpModel.InterpretationRanges.Add(variable.Value.GreaterOrEqualThanZeroRange());
* });
* });*/
}
// only integers we are done...
return(lpModel);
}
public IActionResult DualSimplex([FromBody] LPModelDto lpModelDto)
{
bool wrongFormat = false;
string message = null;
try
{
lpModelDto.Validate();
}
catch (ArgumentException e)
{
wrongFormat = true;
message = string.Format(Messages.WRONG_FORMAT_CHECK_ARG, e.ParamName);
}
if (wrongFormat)
{
return(BadRequest(new { success = false, message = message }));
}
var lpModel = lpModelDto.MapTo(new LPModel());
try
{
lpModel.DualSimplex();
var solution = lpModel.GetSolutionFromDictionary(lpModelDto.MapTo(new LPModel()).Objective.Function);
}
catch (SimplexAlgorithmExectionException e)
{
message = e.ExecutionError == SimplexAlgorithmExectionErrorType.NoSolution ?
Messages.SIMPLEX_RESULT_NO_SOLUTION :
Messages.SIMPLEX_RESULT_NO_LIMIT;
}
return(Json(new { success = true, message = message }));
}
public async Task <IActionResult> Solve([FromBody] LPModelDto lpModelDto, bool integerProgramming = false)
{
bool wrongFormat = false;
string message = null;
SimplexSolutionDto solution = null;
LPModel lpModel = null;
try
{
lpModelDto.Validate();
}
catch (ArgumentException e)
{
wrongFormat = true;
message = string.Format(Messages.WRONG_FORMAT_CHECK_ARG, e.ParamName);
}
if (wrongFormat)
{
return(BadRequest(new { success = false, message = message }));
}
if (integerProgramming)
{
try
{
lpModel = Gomory.RunGomory(lpModelDto);
solution = lpModel.GetSolutionFromDictionary(lpModelDto.MapTo(new LPModel()).Objective.Function);
}
catch (SimplexAlgorithmExectionException e)
{
message = e.ExecutionError == SimplexAlgorithmExectionErrorType.NoSolution ?
Messages.SIMPLEX_INT_RESULT_NO_SOLUTION :
Messages.SIMPLEX_INT_RESULT_NO_LIMIT;
}
}
else
{
lpModel = lpModelDto.MapTo(new LPModel());
try
{
lpModel.TwoPhaseSimplex();
solution = lpModel.GetSolutionFromDictionary(lpModelDto.MapTo(new LPModel()).Objective.Function);
}
catch (SimplexAlgorithmExectionException e)
{
message = e.ExecutionError == SimplexAlgorithmExectionErrorType.NoSolution ?
Messages.SIMPLEX_RESULT_NO_SOLUTION :
Messages.SIMPLEX_RESULT_NO_LIMIT;
}
catch (Exception)
{
message = Messages.GENERAL_ERROR;
}
}
if (message == Messages.GENERAL_ERROR)
{
return(StatusCode(500, new { success = false, message = message }));
}
var lpTask = new LpTask
{
LPModelAsJson = JsonConvert.SerializeObject(lpModelDto),
SolutionAsJson = JsonConvert.SerializeObject(new LPTaskResultDto {
SolutionFound = solution != null, Message = message, Solution = solution
}),
SolvedAt = DateTimeOffset.Now,
IntegerProgramming = integerProgramming
};
await _lpTaskOperations.Add(lpTask);
return(Json(new { success = true, taskId = lpTask.Id }));
}
