Zedgraph plotting real time graph with fast input rate

Question

I am plotting real time graph using RollingPointPairList of Zedgraph. I am receiving 100 point per second and trying to plot 100 point per second. But zedgraph shows lag and is able to plot only maximum 20 point per second. I am using following code for plotting

    RollingPointPairList samp = new RollingPointPairList(105);

    private void Form1_Load(object sender, EventArgs e)
    {
        CreateGraph(zg1);
        SetSize();
    }
    int x1 = 0;
    private void TimerEventProcessor(int[] diff)
    {
        zg1.GraphPane.XAxis.Scale.MaxAuto = true;
        x1 += 1;
        samp.Add(diff[0], x1);
        if (samp.Count >= 100)
        {
            zg1.AxisChange();
            zg1.Invalidate();
            zg1.Refresh();
            Thread.Sleep(50);
        }
    }

    private void Form1_Resize(object sender, EventArgs e)
    {
        SetSize();
    }

    private void SetSize()
    {
        zg1.Location = new Point(10, 10);
        zg1.Size = new Size(this.ClientRectangle.Width - 10, this.ClientRectangle.Height - 10);
    }

    private void CreateGraph(ZedGraphControl zgc)
    {

        GraphPane myPane = zgc.GraphPane;
        myPane.Title.Text = "Test";
        myPane.XAxis.Title.Text = "X Value";
        myPane.YAxis.Title.Text = "Y Axis";

        LineItem myCurve;
        myCurve= myPane.AddCurve("Curve 1", samp, Color.Blue, SymbolType.Star);

        myCurve.Symbol.Fill = new Fill(Color.White);
        myPane.Chart.Fill = new Fill(Color.White, Color.LightGoldenrodYellow, 45F);
        myPane.Fill = new Fill(Color.White, Color.FromArgb(220, 220, 255), 45F);

        zgc.AxisChange();
        zgc.Refresh();
    }

Thus is their any way of improving my code so that I can plot 100 points or more per second.

Answer 1

Drawing 100 dots per seconds is far from ZedGraph limits. I suspect the bottleneck is not ZedGraph. To be able to reproduce your use case the best I can, I quickly did this piece of code that throws the maximum dots per seconds it can through a ZedGraph control I initialized the same way as you:

using System;
using System.ComponentModel;
using System.Drawing;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;
using ZedGraph;

namespace WindowsFormsApplication1 {

    static class Program {
        /// <summary>
        /// Point d'entrée principal de l'application.
        /// </summary>
        [STAThread]
        static void Main() {
            Application.Run(new Form1());
        }

        class Form1 : Form {
            ZedGraphControl zgc;
            System.Windows.Forms.Label lbl;

            public Form1() {
                this.WindowState = FormWindowState.Maximized;


                lbl = new System.Windows.Forms.Label { Parent = this, Dock = DockStyle.Bottom, AutoSize = false, TextAlign = ContentAlignment.MiddleCenter };
                zgc = new ZedGraphControl {
                    Parent = this,
                    Dock = DockStyle.Fill,
                    Margin = new Padding(10)
                };

                var myPane = zgc.GraphPane;
                myPane.Title.Text = "Test";
                myPane.XAxis.Title.Text = "X Value";
                myPane.YAxis.Title.Text = "Y Axis";
                myPane.XAxis.Scale.MaxAuto = true;

                var myCurve = myPane.AddCurve("Curve 1", samp, Color.Blue, SymbolType.Star);
                myCurve.Symbol.Fill = new Fill(Color.White);
                myPane.Chart.Fill = new Fill(Color.White, Color.LightGoldenrodYellow, 45F);
                myPane.Fill = new Fill(Color.White, Color.FromArgb(220, 220, 255), 45F);
            }

            RollingPointPairList samp = new RollingPointPairList(105);
            int c;

            CancellationTokenSource cts = new CancellationTokenSource();

            protected override void OnLoad(EventArgs e) {
                base.OnLoad(e);

                var t = new System.Timers.Timer { Interval = 1000 };
                t.Elapsed += (sender, eventargs) => { this.BeginInvoke(new Action(() => { lbl.Text = "Dot per seconds: " + c.ToString(); c = 0; })); };
                t.Start();

                Task.Run(() => {
                    var r = new Random();
                    while(!cts.IsCancellationRequested) {
                        TimerEventProcessor(r.Next(-10, 10));
                    };
                });

            }

            protected override void OnClosing(CancelEventArgs e) {
                cts.Cancel();
                cts.Token.WaitHandle.WaitOne();
                base.OnClosing(e);
            }

            int x1 = 0;

            void TimerEventProcessor(int d) {
                x1++; c++;
                samp.Add(d, x1);
                zgc.AxisChange();
                zgc.Invalidate();
            }
        }
    }
}

If I wrongly assumed how your code is supposed to run, please let me know. However, it runs fine on my machine.

IMHO, the advices I use to give when someone uses ZedGraph in my team are:

• Do not invoke the Invalidate method more than necessary. (Your code is using Invalidate, then Refresh. As Refresh performs an invalidation, your code do it twice)
• AxisChange method is only useful if Auto scaling is used (Your code is ok with this)
• Do not perform CPU intensive processing on the UI thread.

I suspect this last point to be the reason of your bottleneck: receiving the packet could be better achieved on a separate thread that invokes Invalidate on the ZedGraph control using the windows Forms SynchronizationContext.