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我正在运行一个代码，该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。我将模型设置为传递成分和营养素的最小值和最大值（成分百分比会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;
    }

结果，我得到了它所设置的决定的最小值，这意味着没有找到解决方案。我的问题是：为什么求解器要考虑决策中设置的最小值，而不是为每个决策计算适当的值？

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1 回答 1

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这是我在建模模型时的错误。代码运行良好。但它确实帮助我通过创建一个 txt 文件并将我的所有约束添加到它来解决问题，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 以便我可以检查为求解模型而设置的所有约束。我的问题中的代码已更新，因此如果您需要，可以检查如何创建 txt 和 oml 文件。

于 2016-08-24T19:41:37.980 回答