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Concurrency Hazards: False Sharing

, 10 Jan 2010
False sharing and how to detect and avoid it.
FalseSharing_bin.zip
FalseSharing_src.zip
FalseSharing
FalseSharingDemo
Properties
Settings.settings
ZedGraph.dll
namespace FalseSharingDemo
{
	partial class Form1
	{
		/// <summary>
		/// Required designer variable.
		/// </summary>
		private System.ComponentModel.IContainer components;

		/// <summary>
		/// Clean up any resources being used.
		/// </summary>
		/// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
		protected override void Dispose( bool disposing )
		{
			if ( disposing && ( components != null ) )
			{
				components.Dispose();
			}
			base.Dispose( disposing );
		}

		#region Windows Form Designer generated code

		/// <summary>
		/// Required method for Designer support - do not modify
		/// the contents of this method with the code editor.
		/// </summary>
		private void InitializeComponent()
		{
			this.components = new System.ComponentModel.Container();
			this.zg = new ZedGraph.ZedGraphControl();
			this.btnTest = new System.Windows.Forms.Button();
			this.pb = new System.Windows.Forms.ProgressBar();
			this.tbAccuracy = new System.Windows.Forms.TrackBar();
			this.label2 = new System.Windows.Forms.Label();
			this.cbOneWriter = new System.Windows.Forms.CheckBox();
			this.groupBox1 = new System.Windows.Forms.GroupBox();
			this.label4 = new System.Windows.Forms.Label();
			this.label3 = new System.Windows.Forms.Label();
			this.gbGraphOptions = new System.Windows.Forms.GroupBox();
			this.rbEfficiency = new System.Windows.Forms.RadioButton();
			this.rbSpeedup = new System.Windows.Forms.RadioButton();
			this.groupBox1.SuspendLayout();
			this.gbGraphOptions.SuspendLayout();
			this.SuspendLayout();
			// 
			// zg
			// 
			this.zg.Anchor = ( ( System.Windows.Forms.AnchorStyles ) ( ( ( ( System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Bottom )
						| System.Windows.Forms.AnchorStyles.Left )
						| System.Windows.Forms.AnchorStyles.Right ) ) );
			this.zg.Location = new System.Drawing.Point( 12, 157 );
			this.zg.Name = "zg";
			this.zg.ScrollGrace = 0D;
			this.zg.ScrollMaxX = 0D;
			this.zg.ScrollMaxY = 0D;
			this.zg.ScrollMaxY2 = 0D;
			this.zg.ScrollMinX = 0D;
			this.zg.ScrollMinY = 0D;
			this.zg.ScrollMinY2 = 0D;
			this.zg.Size = new System.Drawing.Size( 560, 393 );
			this.zg.TabIndex = 7;
			// 
			// btnTest
			// 
			this.btnTest.Location = new System.Drawing.Point( 134, 39 );
			this.btnTest.Name = "btnTest";
			this.btnTest.Size = new System.Drawing.Size( 75, 23 );
			this.btnTest.TabIndex = 3;
			this.btnTest.Text = "Start";
			this.btnTest.UseVisualStyleBackColor = true;
			this.btnTest.Click += new System.EventHandler( this.btnTest_Click );
			// 
			// pb
			// 
			this.pb.Anchor = ( ( System.Windows.Forms.AnchorStyles ) ( ( ( System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Left )
						| System.Windows.Forms.AnchorStyles.Right ) ) );
			this.pb.Location = new System.Drawing.Point( 12, 128 );
			this.pb.Name = "pb";
			this.pb.Size = new System.Drawing.Size( 560, 23 );
			this.pb.TabIndex = 6;
			// 
			// tbAccuracy
			// 
			this.tbAccuracy.Location = new System.Drawing.Point( 6, 35 );
			this.tbAccuracy.Maximum = 9;
			this.tbAccuracy.Minimum = 1;
			this.tbAccuracy.Name = "tbAccuracy";
			this.tbAccuracy.Size = new System.Drawing.Size( 104, 45 );
			this.tbAccuracy.TabIndex = 1;
			this.tbAccuracy.Value = 3;
			// 
			// label2
			// 
			this.label2.AutoSize = true;
			this.label2.Location = new System.Drawing.Point( 33, 19 );
			this.label2.Name = "label2";
			this.label2.Size = new System.Drawing.Size( 51, 13 );
			this.label2.TabIndex = 0;
			this.label2.Text = "accuracy";
			// 
			// cbOneWriter
			// 
			this.cbOneWriter.AutoSize = true;
			this.cbOneWriter.Location = new System.Drawing.Point( 12, 96 );
			this.cbOneWriter.Name = "cbOneWriter";
			this.cbOneWriter.Size = new System.Drawing.Size( 197, 17 );
			this.cbOneWriter.TabIndex = 2;
			this.cbOneWriter.Text = "Only first thread writes ( others read )";
			this.cbOneWriter.UseVisualStyleBackColor = true;
			// 
			// groupBox1
			// 
			this.groupBox1.Controls.Add( this.label4 );
			this.groupBox1.Controls.Add( this.label3 );
			this.groupBox1.Location = new System.Drawing.Point( 239, 13 );
			this.groupBox1.Name = "groupBox1";
			this.groupBox1.Size = new System.Drawing.Size( 212, 69 );
			this.groupBox1.TabIndex = 4;
			this.groupBox1.TabStop = false;
			this.groupBox1.Text = " #define ";
			// 
			// label4
			// 
			this.label4.AutoSize = true;
			this.label4.Location = new System.Drawing.Point( 14, 42 );
			this.label4.Name = "label4";
			this.label4.Size = new System.Drawing.Size( 180, 13 );
			this.label4.TabIndex = 1;
			this.label4.Text = "Spacing: distance between counters";
			// 
			// label3
			// 
			this.label3.AutoSize = true;
			this.label3.Location = new System.Drawing.Point( 14, 22 );
			this.label3.Name = "label3";
			this.label3.Size = new System.Drawing.Size( 184, 13 );
			this.label3.TabIndex = 0;
			this.label3.Text = "Padding: index of first counter in array";
			// 
			// gbGraphOptions
			// 
			this.gbGraphOptions.Controls.Add( this.rbEfficiency );
			this.gbGraphOptions.Controls.Add( this.rbSpeedup );
			this.gbGraphOptions.Location = new System.Drawing.Point( 464, 13 );
			this.gbGraphOptions.Name = "gbGraphOptions";
			this.gbGraphOptions.Size = new System.Drawing.Size( 108, 100 );
			this.gbGraphOptions.TabIndex = 5;
			this.gbGraphOptions.TabStop = false;
			this.gbGraphOptions.Text = "Graph Options";
			// 
			// rbEfficiency
			// 
			this.rbEfficiency.AutoSize = true;
			this.rbEfficiency.Checked = true;
			this.rbEfficiency.Location = new System.Drawing.Point( 17, 52 );
			this.rbEfficiency.Name = "rbEfficiency";
			this.rbEfficiency.Size = new System.Drawing.Size( 71, 17 );
			this.rbEfficiency.TabIndex = 1;
			this.rbEfficiency.TabStop = true;
			this.rbEfficiency.Text = "Efficiency";
			this.rbEfficiency.UseVisualStyleBackColor = true;
			// 
			// rbSpeedup
			// 
			this.rbSpeedup.AutoSize = true;
			this.rbSpeedup.Location = new System.Drawing.Point( 17, 29 );
			this.rbSpeedup.Name = "rbSpeedup";
			this.rbSpeedup.Size = new System.Drawing.Size( 68, 17 );
			this.rbSpeedup.TabIndex = 0;
			this.rbSpeedup.Text = "Speedup";
			this.rbSpeedup.UseVisualStyleBackColor = true;
			// 
			// Form1
			// 
			this.AutoScaleDimensions = new System.Drawing.SizeF( 6F, 13F );
			this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
			this.ClientSize = new System.Drawing.Size( 584, 562 );
			this.Controls.Add( this.gbGraphOptions );
			this.Controls.Add( this.groupBox1 );
			this.Controls.Add( this.cbOneWriter );
			this.Controls.Add( this.label2 );
			this.Controls.Add( this.tbAccuracy );
			this.Controls.Add( this.pb );
			this.Controls.Add( this.btnTest );
			this.Controls.Add( this.zg );
			this.Name = "Form1";
			this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
			this.Text = "False Sharing Demo";
			this.groupBox1.ResumeLayout( false );
			this.groupBox1.PerformLayout();
			this.gbGraphOptions.ResumeLayout( false );
			this.gbGraphOptions.PerformLayout();
			this.ResumeLayout( false );
			this.PerformLayout();

		}

		#endregion

		private ZedGraph.ZedGraphControl zg;
		private System.Windows.Forms.Button btnTest;
		private System.Windows.Forms.ProgressBar pb;
		private System.Windows.Forms.TrackBar tbAccuracy;
		private System.Windows.Forms.Label label2;
		private System.Windows.Forms.CheckBox cbOneWriter;
		private System.Windows.Forms.GroupBox groupBox1;
		private System.Windows.Forms.Label label4;
		private System.Windows.Forms.Label label3;
		private System.Windows.Forms.GroupBox gbGraphOptions;
		private System.Windows.Forms.RadioButton rbEfficiency;
		private System.Windows.Forms.RadioButton rbSpeedup;
	}
}

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About the Author

Nicholas Butler

United Kingdom United Kingdom

I built my first computer, a Sinclair ZX80, on my 11th birthday in 1980.
In 1992, I completed my Computer Science degree and built my first PC.
I discovered C# and .NET 1.0 Beta 1 in late 2000 and loved them immediately.
I have been writing concurrent software professionally, using multi-processor machines, since 1995.
 
In real life, I have spent 3 years travelling abroad,
I have held a UK Private Pilots Licence for 20 years,
and I am a PADI Divemaster.
 
I now live near idyllic Bournemouth in England.
 
If you would like help with multithreading, please contact me via my website:
 
 
I can work 'virtually' anywhere!

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