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Editorial Team
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Asked: 2026-05-26T11:43:39+00:00

I’ve read several articles and questions/answers that conclude the best practice is to let

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I’ve read several articles and questions/answers that conclude the best practice is to let the JIT compiler do all the optimization for inline function calls. Makes sense.

What about inline variable declarations? Does the compiler optimize these as well?

That is, will this:

        Dim h = (a + b + c) / 2       'Half-Perimeter

        If maxEdgeLength / (Math.Sqrt(h * (h - a) * (h - b) * (h - c)) / h) <= MaximumTriangleAspectRatio Then
           'Do stuff here.
        End If

Have better performance than this:

        Dim perimeter = a + b + c   'Perimeter
        Dim h = perimeter / 2       'Half-Perimeter

        Dim area = Math.Sqrt(h * (h - a) * (h - b) * (h - c)) 'Heron's forumula.
        Dim inradius = area / h
        Dim aspectRatio = maxEdgeLength / inradius

        If aspectRatio <= MaximumTriangleAspectRatio Then
            'Do stuff here.
        End If

Of course I prefer the latter because it’s easier to read and debug, but I can’t afford the performance degradation if it exists.

Note: I have already identified this code as a bottleneck — No need for retorts about premature optimization. 🙂

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1 Answer

  1. Editorial Team

    Temporary variables having names or not is a non-issue.

    But you can optimize that inequality significantly.

    Your code was:

    If maxEdgeLength / (Math.Sqrt(h * (h - a) * (h - b) * (h - c)) / h) <= MaximumTriangleAspectRatio Then

    Multiply both sides by the square root, eliminating division (inequality is preserved, because square root cannot return a negative number):

    If maxEdgeLength <= (Math.Sqrt(h * (h - a) * (h - b) * (h - c)) / h) * MaximumTriangleAspectRatio Then

    Now, square both sides to eliminate that expensive square root:

    If maxEdgeLength * maxEdgeLength <= h * (h - a) * (h - b) * (h - c) / h / h * MaximumTriangleAspectRatio * MaximumTriangleAspectRatio Then

    Cancel, and multiply by h.

    If maxEdgeLength * maxEdgeLength * h <= (h - a) * (h - b) * (h - c) * MaximumTriangleAspectRatio * MaximumTriangleAspectRatio Then

    This will be a lot faster. If this calculation is repeated, consider caching the results of part of this expression for even more improvement.

    Use comments to explain the formula. Getting rid of a Math.Sqrt call in a bottleneck function is worth writing the expression in a less-than-simple format.

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