CODEWITHSUNDEEP
c#math
user21139719
user21139719

Reputation:

Is there a faster way to compare these decimals?

I have a stream of decimals and I am trying to compare the most recent decimal to the difference of the last 6 decimals, I may increase this number

I have the following class

public class CompareRandom
{
    private const decimal DIFFERENCE = 1.8m;

    public decimal a;
    public decimal b;
    public decimal c;
    public decimal d;
    public decimal e;
    public decimal f;
    public decimal g;

    public bool Compare(decimal num)
    {
        this.g = this.f;
        this.f = this.e;
        this.e = this.d;
        this.d = this.c;
        this.c = this.b;
        this.b = this.a;
        this.a = num;

        if (b != decimal.Zero && b / DIFFERENCE > a)
        {
            return true;
        }

        if (c != decimal.Zero && c / DIFFERENCE > a)
        {

            return true;
        }

        if (d != decimal.Zero && d / DIFFERENCE > a)
        {
            return true;
        }

        if (e != decimal.Zero && e / DIFFERENCE > a)
        {
            return true;
        }

        if (f != decimal.Zero && f / DIFFERENCE > a)
        {
            return true;
        }

        if (g != decimal.Zero && g / DIFFERENCE > a)
        {
            return true;
        }

        return false;
    }
}

Then I initialize it as volatile

volatile static CompareRandom CompareRandom = new CompareRandom();

Then I call CompareRandom.Compare(value) synchronously as part of a loop that updates every 1ms to compare the values.

The part I am the most interested in knowing if there is a faster way to do is this part

    this.g = this.f;
    this.f = this.e;
    this.e = this.d;
    this.d = this.c;
    this.c = this.b;
    this.b = this.a;
    this.a = num;

A successful answer will demonstrate a faster execution of the method Compare

See if you can make it faster:

https://dotnetfiddle.net/tLw8qM

https://dotnetfiddle.net/jd0bSF

Upvotes: 0

Views: 165

Answers (1)

Jon Skeet
Jon Skeet

Reputation: 1500135

You don't need to perform the division every time. Instead, multiply a by DIFFERENCE to obtain a threshold:

// Name changed to be more conventional
private const decimal Difference = 1.8m;

public bool Compare(decimal num)
{
    g = f;
    f = e;
    e = d;
    d = c;
    c = b;
    b = a;
    a = num;
    var threshold = num * Difference;
    return (b != decimal.Zero && b > threshold) ||
           (c != decimal.Zero && c > threshold) ||
           (d != decimal.Zero && d > threshold) ||
           (e != decimal.Zero && e > threshold) ||
           (f != decimal.Zero && f > threshold) ||
           (g != decimal.Zero && g > threshold);
};

As asides:

  • It's odd for a Compare method to return bool rather than an integer; given that it's not the "common" meaning of Compare, it's probably worth renaming it for clarity
  • It's very odd for a comparison method to change the state of an object, as this is doing (assigning to a) - another good reason to change the name.

Using a collection instead of separate variables would make all of this more maintainable, but I'd be surprised if it improved the speed.

Upvotes: 2

Related Questions