Question

我正在运行一个代码，需要计算构成动物食品的适当成分百分比。为了做到这一点，我正在使用MS求解器基础。我设定模型通过成分和营养素的最小值和最大值（成分百分比干扰或多或少的营养素）。我需要组成动物食品的最便宜（最小化）成本。这是我的代码。

  private Solution FormularRacao()
    {
        var ingredientesRacao = _formulacaoRacao.CarregarIngredientesNutrientesFormulacao(true);
        var nutrientes = _formulacaoRacao.CarregarIngredientesNutrientesFormulacao(false);
        var formulacao = _formulacaoRacao.CarregarFormulacao();

        SolverContext context = SolverContext.GetContext();
        context.ClearModel();

        Model model = context.CreateModel();

        var objetivo = new SumTermBuilder(ingredientesRacao.Count);
        var totalIngrediente = new SumTermBuilder(ingredientesRacao.Count);

        List<SumTermBuilder> listaTotalNutriente = new List<SumTermBuilder>();

        //Set decisions
        foreach (var item in ingredientesRacao)
        {
            item.Nome = TratarNome(item.Nome);

            Decision d = new Decision(Domain.RealRange(Convert.ToDouble(item.Minimo), Convert.ToDouble(item.Maximo)), "d_" + item.Nome);

            model.AddDecision(d);

            objetivo.Add(Model.Product(d, Convert.ToDouble(item.Custo)));
            totalIngrediente.Add(d);
            listaTotalNutriente.Add(new SumTermBuilder(nutrientes.Count));
        }

        var SomaIngrediente = totalIngrediente.ToTerm();

        //sum of decisions values must be equal 100
        model.AddConstraint("c_totalIngrediente", SomaIngrediente == 100);

        //totalIngrediente;
        model.AddGoal("racao", GoalKind.Minimize, objetivo.ToTerm());

        int indexIngrediente = 0;
        int indexNutriente = 0;

        //each ingredient contributes with nutrients
        //each nutrient has a min and max set            
        foreach (var ingredienteRacao in ingredientesRacao)
        {
            Ingrediente ingrediente = _formulacaoRacao.CarregarIngrediente(ingredienteRacao.Id);
            indexNutriente = 0;
            ingredienteRacao.Nome = TratarNome(ingredienteRacao.Nome);
            Decision d = model.Decisions.First(x => x.Name == "d_" + ingredienteRacao.Nome);

            foreach (var nutriente in nutrientes)
            {
                var valor = new object();

                if (nutriente.AminoacidoDigestivo.Equals("S"))
                {
                    var aminoacidoDigestivo = _formulacaoRacao.CarregarAminoacidoDigestivo(ingredienteRacao.Id);
                    valor = aminoacidoDigestivo.GetType().GetProperty(nutriente.Nome).GetValue(aminoacidoDigestivo, null);
                }
                else
                {
                    nutriente.Nome = TratarNomeNutriente(nutriente.Nome);
                    valor = ingrediente.GetType().GetProperty(nutriente.Nome).GetValue(ingrediente, null);
                }

                var proporcaoNutriente = Convert.ToDouble(valor.ToString()) * d;

                listaTotalNutriente[indexNutriente].Add(proporcaoNutriente / 100);

                if (indexIngrediente == ingredientesRacao.Count - 1) //last iteration
                {
                    var totalNutriente = listaTotalNutriente[indexNutriente].ToTerm();
                    if (nutriente.Minimo == nutriente.Maximo)
                       model.AddConstraint("c_" + nutriente.Nome, totalNutriente == Convert.ToDouble(nutriente.Maximo));                        
                    else
                        model.AddConstraint("c" + nutriente.Nome, Convert.ToDouble(nutriente.Minimo) <= totalNutriente <= Convert.ToDouble(nutriente.Maximo));                        
                }

                indexNutriente++;
            }
            indexIngrediente++;
        }            

        //saves the model
        TextWriter tw = new StreamWriter("Path\file.oml");
        context.SaveModel(FileFormat.OML, tw);
        tw.Close();

        //Imprime o modelo
        TextWriter txt = new StreamWriter("Path\file.txt");
        foreach (var item in model.Constraints.ToList())
        {
            txt.WriteLine(item.Name + ":  " + item.Expression);
            txt.WriteLine();
        }
        txt.Close();

        Solution solution = context.Solve();

        return solution;
    }

我得到了设置决策的最小值，这意味着找不到解决方案。我的问题是：为什么求解者考虑决策中设定的最小值而不是为每个决策计算适当的值？

Answer 1

模型建模时我的错误。代码工作正常。但它确实帮助我通过创建一个txt文件并添加了我所有的约束来解决问题，所以我可以仔细检查我设置的约束，还可以创建一个模型文件（oml）并将其导入Excel，这样我就可以检查了所有约束设置为解决模型。代码在我的问题中更新，如果您需要，可以检查如何创建txt和oml文件。

求解器获得决策中设置的最小值

1 个答案: