1

我试图做 ML.net 的例子来预测纽约的出租车票价，但是当我完成教程时有消息：程序不包含适合入口点的静态“主要”方法

这是我做的代码：

类程序.cs

using System;
using System.IO;
using Microsoft.ML;
using Microsoft.ML.Data;
using Microsoft.ML.Models;
using Microsoft.ML.Trainers;
using Microsoft.ML.Transforms;
using System.Threading.Tasks;

namespace TaxiFarePrediction2
{
    public class Program
    {
        static readonly string _datapath = Path.Combine(Environment.CurrentDirectory, "Data", "taxi-fare-train.csv");
        static readonly string _testdatapath = Path.Combine(Environment.CurrentDirectory, "Data", "taxi-fare-test.csv");
        static readonly string _modelpath = Path.Combine(Environment.CurrentDirectory, "Data", "Model.zip");


        static async Task Main(string[] args)
        {
            PredictionModel<TaxiTrip, TaxiTripFarePrediction> model = await Train();
            Evaluate(model);
            TaxiTripFarePrediction prediction = model.Predict(TestTrips.Trip1);
            Console.WriteLine("Predicted fare: {0}, actual fare: 29.5", prediction.FareAmount);
        }


        public static async Task<PredictionModel<TaxiTrip, TaxiTripFarePrediction>> Train()
        {
            var pipeline = new LearningPipeline
            {
                new TextLoader(_datapath).CreateFrom<TaxiTrip>(useHeader: true, separator: ','),
                new ColumnCopier(("FareAmount", "Label")),
                new CategoricalOneHotVectorizer(
                    "VendorId",
                    "RateCode",
                    "PaymentType"),
                new ColumnConcatenator(
                    "Features",
                    "VendorId",
                    "RateCode",
                    "PassengerCount",
                    "TripDistance",
                    "PaymentType"),
                new FastTreeRegressor()
            };
            PredictionModel<TaxiTrip, TaxiTripFarePrediction> model = pipeline.Train<TaxiTrip, TaxiTripFarePrediction>();
            await model.WriteAsync(_modelpath);
            return model;
        }

        private static void Evaluate(PredictionModel<TaxiTrip, TaxiTripFarePrediction> model)
        {
            var testData = new TextLoader(_testdatapath).CreateFrom<TaxiTrip>(useHeader: true, separator: ',');
            var evaluator = new RegressionEvaluator();
            RegressionMetrics metrics = evaluator.Evaluate(model, testData);
            Console.WriteLine($"Rms = {metrics.Rms}");
            Console.WriteLine($"RSquared = {metrics.RSquared}");
        }


    }
}

类 TaxiTrip.cs

using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.ML.Runtime.Api;

namespace TaxiFarePrediction2
{
    public class TaxiTrip
    {
        [Column("0")]
        public string VendorId;

        [Column("1")]
        public string RateCode;

        [Column("2")]
        public float PassengerCount;

        [Column("3")]
        public float TripTime;

        [Column("4")]
        public float TripDistance;

        [Column("5")]
        public string PaymentType;

        [Column("6")]
        public float FareAmount;
    }

    public class TaxiTripFarePrediction
    {
        [ColumnName("Score")]
        public float FareAmount;
    }
}

类 TestTrips.cs

using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.ML.Runtime.Api;

namespace TaxiFarePrediction2
{
    public class TaxiTrip
    {
        [Column("0")]
        public string VendorId;

        [Column("1")]
        public string RateCode;

        [Column("2")]
        public float PassengerCount;

        [Column("3")]
        public float TripTime;

        [Column("4")]
        public float TripDistance;

        [Column("5")]
        public string PaymentType;

        [Column("6")]
        public float FareAmount;
    }

    public class TaxiTripFarePrediction
    {
        [ColumnName("Score")]
        public float FareAmount;
    }
}

该教程位于：https ://docs.microsoft.com/en-us/dotnet/machine-learning/tutorials/taxi-fare

请帮我做这个例子。

4

1 回答 1

4

在 c# 7.1 之前，main 方法不支持 asycn，如果您使用早期版本，您可以启动一次 main，然后在 main 方法中创建可以异步的任务。

你可以写Chris Moschini提到的东西

class Program
{
static void Main(string[] args)
{
    Task.Run(async () =>
    {
        // Do any async anything you need here without worry
    }).GetAwaiter().GetResult();
}

您发布的链接清楚地提到了指定的 c# 版本...

因为 async Main 方法是 C# 7.1 中添加的功能，并且项目的默认语言版本是 C# 7.0，所以您需要将语言版本更改为 C# 7.1 或更高版本。为此，请右键单击解决方案资源管理器中的项目节点并选择属性。选择构建选项卡并选择高级按钮。在下拉列表中，选择 C# 7.1（或更高版本）。选择确定按钮。

一个很好的阅读 main 与 async

于 2018-08-27T06:23:20.723 回答