Question

I am using such code in multithreading:

Old example:

  class All
     {
        object lockAll = new object();
        public All ()
        {
           lock(lockAll)
           {
               double res= Magnitude(1d, 0.1d , 0.2d);
           }
        }
        private double Magnitude(double X, double Y, double Z)
        {
           return Math.Sqrt(X * X + Y * Y + Z * Z);
        }
     }

But i see that sometimes res is 1.3 * 10 ^-314. Why??? All is locked.:
Part of real code:

class PointSensors : IDisposable
    {
object lockAcs = new object(); //Can it be non static? I think yes
object lockMag = new object();
// When i got info from sensors. Multitheading method called many times every time in new thread
 public void OnSensorChanged(SensorEvent ev)
        {
            Sensor curS = ev.Sensor;
            long timeStamp = ev.Timestamp;
              // Vector from sensors
             Vector3 vector = new Vector3(ev.Values[0], ev.Values[1], ev.Values[2]);
                if (curS.Type == SensorType.Accelerometer)
                {
                    lock (lockAcs)
                    {
                       double TotalAcseleration = vector.Magnitude - 9.8d;
                       ...
                    }
                }

                if (curS.Type == SensorType.MagneticField))
                {
                    lock (lockMag)
                    {
                       double TotalMagVect = vector.Magnitude ;
                       ...
                    }
                }


        }
}

And sometimes Math functions give crazy results.

Answer 1

Your lock doesn’t make sense since res is not a shared variable. Its scope only exists within the lock so no other thread will have access to it anyway.