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Is there a reason for mulitplying by an integer 'x', then dividing by that same 'x' as a double? [duplicate]

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I was running through some code the other day and found this line which I thought was peculiar.

Math.Round(20 * (bytes / 1024.0 / 1024.0 / 1024.0), MidpointRounding.AwayFromZero) / 20.0);

I can't understand why they are multiplying by int 20, and then dividing by float 20.0

My initial suspicion is that it had something to do with either rounding or precision, but I couldn't find the answer on here or on Google (at least not with my search terms). What is the purpose of doing this sort of operation?

edit

For context, this line of code is intended to convert the variable bytes into Gigabytes

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Sean Sailer Avatar asked Aug 28 '19 13:08

Sean Sailer

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1 Answers

As Andrew Morton suggested in the comments, this will round to the next highest 0.05 GB increment -- here's some code and a fiddle to test it

float bytes;
for (bytes = 0; bytes < 1000000000; bytes += 5000000)
{
    var x = Math.Round(20 * (bytes / 1024.0 / 1024.0 / 1024.0), MidpointRounding.AwayFromZero) / 20.0;
    var y = Math.Round(bytes / 1024.0 / 1024.0 / 1024.0, MidpointRounding.AwayFromZero);
    Console.WriteLine("Bytes: {0} -- x: {1}, y: {2}", bytes, x , y);
}

produces the following output:


Bytes: 0 -- x: 0, y: 0
Bytes: 5000000 -- x: 0, y: 0
Bytes: 1E+07 -- x: 0, y: 0
Bytes: 1.5E+07 -- x: 0, y: 0
Bytes: 2E+07 -- x: 0, y: 0
Bytes: 2.5E+07 -- x: 0, y: 0
Bytes: 3E+07 -- x: 0.05, y: 0
Bytes: 3.5E+07 -- x: 0.05, y: 0
Bytes: 4E+07 -- x: 0.05, y: 0
Bytes: 4.5E+07 -- x: 0.05, y: 0
Bytes: 5E+07 -- x: 0.05, y: 0
Bytes: 5.5E+07 -- x: 0.05, y: 0
Bytes: 6E+07 -- x: 0.05, y: 0
Bytes: 6.5E+07 -- x: 0.05, y: 0
Bytes: 7E+07 -- x: 0.05, y: 0
Bytes: 7.5E+07 -- x: 0.05, y: 0
Bytes: 8E+07 -- x: 0.05, y: 0
Bytes: 8.5E+07 -- x: 0.1, y: 0
Bytes: 9E+07 -- x: 0.1, y: 0
Bytes: 9.5E+07 -- x: 0.1, y: 0
Bytes: 1E+08 -- x: 0.1, y: 0
Bytes: 1.05E+08 -- x: 0.1, y: 0
Bytes: 1.1E+08 -- x: 0.1, y: 0
Bytes: 1.15E+08 -- x: 0.1, y: 0
Bytes: 1.2E+08 -- x: 0.1, y: 0
Bytes: 1.25E+08 -- x: 0.1, y: 0
Bytes: 1.3E+08 -- x: 0.1, y: 0
Bytes: 1.35E+08 -- x: 0.15, y: 0
Bytes: 1.4E+08 -- x: 0.15, y: 0
Bytes: 1.45E+08 -- x: 0.15, y: 0
Bytes: 1.5E+08 -- x: 0.15, y: 0
Bytes: 1.55E+08 -- x: 0.15, y: 0
Bytes: 1.6E+08 -- x: 0.15, y: 0
Bytes: 1.65E+08 -- x: 0.15, y: 0
Bytes: 1.7E+08 -- x: 0.15, y: 0
Bytes: 1.75E+08 -- x: 0.15, y: 0
Bytes: 1.8E+08 -- x: 0.15, y: 0
Bytes: 1.85E+08 -- x: 0.15, y: 0
Bytes: 1.9E+08 -- x: 0.2, y: 0
Bytes: 1.95E+08 -- x: 0.2, y: 0
Bytes: 2E+08 -- x: 0.2, y: 0
Bytes: 2.05E+08 -- x: 0.2, y: 0
Bytes: 2.1E+08 -- x: 0.2, y: 0
Bytes: 2.15E+08 -- x: 0.2, y: 0
Bytes: 2.2E+08 -- x: 0.2, y: 0
Bytes: 2.25E+08 -- x: 0.2, y: 0
Bytes: 2.3E+08 -- x: 0.2, y: 0
Bytes: 2.35E+08 -- x: 0.2, y: 0
Bytes: 2.4E+08 -- x: 0.2, y: 0
Bytes: 2.45E+08 -- x: 0.25, y: 0
Bytes: 2.5E+08 -- x: 0.25, y: 0
Bytes: 2.55E+08 -- x: 0.25, y: 0
Bytes: 2.6E+08 -- x: 0.25, y: 0
Bytes: 2.65E+08 -- x: 0.25, y: 0
Bytes: 2.7E+08 -- x: 0.25, y: 0
Bytes: 2.75E+08 -- x: 0.25, y: 0
Bytes: 2.8E+08 -- x: 0.25, y: 0
Bytes: 2.85E+08 -- x: 0.25, y: 0
Bytes: 2.9E+08 -- x: 0.25, y: 0
Bytes: 2.95E+08 -- x: 0.25, y: 0
Bytes: 3E+08 -- x: 0.3, y: 0
Bytes: 3.05E+08 -- x: 0.3, y: 0
Bytes: 3.1E+08 -- x: 0.3, y: 0
Bytes: 3.15E+08 -- x: 0.3, y: 0
Bytes: 3.2E+08 -- x: 0.3, y: 0
Bytes: 3.25E+08 -- x: 0.3, y: 0
Bytes: 3.3E+08 -- x: 0.3, y: 0
Bytes: 3.35E+08 -- x: 0.3, y: 0
Bytes: 3.4E+08 -- x: 0.3, y: 0
Bytes: 3.45E+08 -- x: 0.3, y: 0
Bytes: 3.5E+08 -- x: 0.35, y: 0
Bytes: 3.55E+08 -- x: 0.35, y: 0
Bytes: 3.6E+08 -- x: 0.35, y: 0
Bytes: 3.65E+08 -- x: 0.35, y: 0
Bytes: 3.7E+08 -- x: 0.35, y: 0
Bytes: 3.75E+08 -- x: 0.35, y: 0
Bytes: 3.8E+08 -- x: 0.35, y: 0
Bytes: 3.85E+08 -- x: 0.35, y: 0
Bytes: 3.9E+08 -- x: 0.35, y: 0
Bytes: 3.95E+08 -- x: 0.35, y: 0
Bytes: 4E+08 -- x: 0.35, y: 0
Bytes: 4.05E+08 -- x: 0.4, y: 0
Bytes: 4.1E+08 -- x: 0.4, y: 0
Bytes: 4.15E+08 -- x: 0.4, y: 0
Bytes: 4.2E+08 -- x: 0.4, y: 0
Bytes: 4.25E+08 -- x: 0.4, y: 0
Bytes: 4.3E+08 -- x: 0.4, y: 0
Bytes: 4.35E+08 -- x: 0.4, y: 0
Bytes: 4.4E+08 -- x: 0.4, y: 0
Bytes: 4.45E+08 -- x: 0.4, y: 0
Bytes: 4.5E+08 -- x: 0.4, y: 0
Bytes: 4.55E+08 -- x: 0.4, y: 0
Bytes: 4.6E+08 -- x: 0.45, y: 0
Bytes: 4.65E+08 -- x: 0.45, y: 0
Bytes: 4.7E+08 -- x: 0.45, y: 0
Bytes: 4.75E+08 -- x: 0.45, y: 0
Bytes: 4.8E+08 -- x: 0.45, y: 0
Bytes: 4.85E+08 -- x: 0.45, y: 0
Bytes: 4.9E+08 -- x: 0.45, y: 0
Bytes: 4.95E+08 -- x: 0.45, y: 0
Bytes: 5E+08 -- x: 0.45, y: 0
Bytes: 5.05E+08 -- x: 0.45, y: 0
Bytes: 5.1E+08 -- x: 0.45, y: 0
Bytes: 5.15E+08 -- x: 0.5, y: 0
Bytes: 5.2E+08 -- x: 0.5, y: 0
Bytes: 5.25E+08 -- x: 0.5, y: 0
Bytes: 5.3E+08 -- x: 0.5, y: 0
Bytes: 5.35E+08 -- x: 0.5, y: 0
Bytes: 5.4E+08 -- x: 0.5, y: 1
Bytes: 5.45E+08 -- x: 0.5, y: 1
Bytes: 5.5E+08 -- x: 0.5, y: 1
Bytes: 5.55E+08 -- x: 0.5, y: 1
Bytes: 5.6E+08 -- x: 0.5, y: 1
Bytes: 5.65E+08 -- x: 0.55, y: 1
Bytes: 5.7E+08 -- x: 0.55, y: 1
Bytes: 5.75E+08 -- x: 0.55, y: 1
Bytes: 5.8E+08 -- x: 0.55, y: 1
Bytes: 5.85E+08 -- x: 0.55, y: 1
Bytes: 5.9E+08 -- x: 0.55, y: 1
Bytes: 5.95E+08 -- x: 0.55, y: 1
Bytes: 6E+08 -- x: 0.55, y: 1
Bytes: 6.05E+08 -- x: 0.55, y: 1
Bytes: 6.1E+08 -- x: 0.55, y: 1
Bytes: 6.15E+08 -- x: 0.55, y: 1
Bytes: 6.2E+08 -- x: 0.6, y: 1
Bytes: 6.25E+08 -- x: 0.6, y: 1
Bytes: 6.3E+08 -- x: 0.6, y: 1
Bytes: 6.35E+08 -- x: 0.6, y: 1
Bytes: 6.4E+08 -- x: 0.6, y: 1
Bytes: 6.45E+08 -- x: 0.6, y: 1
Bytes: 6.5E+08 -- x: 0.6, y: 1
Bytes: 6.55E+08 -- x: 0.6, y: 1
Bytes: 6.6E+08 -- x: 0.6, y: 1
Bytes: 6.65E+08 -- x: 0.6, y: 1
Bytes: 6.7E+08 -- x: 0.6, y: 1
Bytes: 6.75E+08 -- x: 0.65, y: 1
Bytes: 6.8E+08 -- x: 0.65, y: 1
Bytes: 6.85E+08 -- x: 0.65, y: 1
Bytes: 6.9E+08 -- x: 0.65, y: 1
Bytes: 6.95E+08 -- x: 0.65, y: 1
Bytes: 7E+08 -- x: 0.65, y: 1
Bytes: 7.05E+08 -- x: 0.65, y: 1
Bytes: 7.1E+08 -- x: 0.65, y: 1
Bytes: 7.15E+08 -- x: 0.65, y: 1
Bytes: 7.2E+08 -- x: 0.65, y: 1
Bytes: 7.25E+08 -- x: 0.7, y: 1
Bytes: 7.3E+08 -- x: 0.7, y: 1
Bytes: 7.35E+08 -- x: 0.7, y: 1
Bytes: 7.4E+08 -- x: 0.7, y: 1
Bytes: 7.45E+08 -- x: 0.7, y: 1
Bytes: 7.5E+08 -- x: 0.7, y: 1
Bytes: 7.55E+08 -- x: 0.7, y: 1
Bytes: 7.6E+08 -- x: 0.7, y: 1
Bytes: 7.65E+08 -- x: 0.7, y: 1
Bytes: 7.7E+08 -- x: 0.7, y: 1
Bytes: 7.75E+08 -- x: 0.7, y: 1
Bytes: 7.8E+08 -- x: 0.75, y: 1
Bytes: 7.85E+08 -- x: 0.75, y: 1
Bytes: 7.9E+08 -- x: 0.75, y: 1
Bytes: 7.95E+08 -- x: 0.75, y: 1
Bytes: 8E+08 -- x: 0.75, y: 1
Bytes: 8.05E+08 -- x: 0.75, y: 1
Bytes: 8.1E+08 -- x: 0.75, y: 1
Bytes: 8.15E+08 -- x: 0.75, y: 1
Bytes: 8.2E+08 -- x: 0.75, y: 1
Bytes: 8.25E+08 -- x: 0.75, y: 1
Bytes: 8.3E+08 -- x: 0.75, y: 1
Bytes: 8.35E+08 -- x: 0.8, y: 1
Bytes: 8.4E+08 -- x: 0.8, y: 1
Bytes: 8.45E+08 -- x: 0.8, y: 1
Bytes: 8.5E+08 -- x: 0.8, y: 1
Bytes: 8.55E+08 -- x: 0.8, y: 1
Bytes: 8.6E+08 -- x: 0.8, y: 1
Bytes: 8.65E+08 -- x: 0.8, y: 1
Bytes: 8.7E+08 -- x: 0.8, y: 1
Bytes: 8.75E+08 -- x: 0.8, y: 1
Bytes: 8.8E+08 -- x: 0.8, y: 1
Bytes: 8.85E+08 -- x: 0.8, y: 1
Bytes: 8.9E+08 -- x: 0.85, y: 1
Bytes: 8.95E+08 -- x: 0.85, y: 1
Bytes: 9E+08 -- x: 0.85, y: 1
Bytes: 9.05E+08 -- x: 0.85, y: 1
Bytes: 9.1E+08 -- x: 0.85, y: 1
Bytes: 9.15E+08 -- x: 0.85, y: 1
Bytes: 9.2E+08 -- x: 0.85, y: 1
Bytes: 9.25E+08 -- x: 0.85, y: 1
Bytes: 9.3E+08 -- x: 0.85, y: 1
Bytes: 9.35E+08 -- x: 0.85, y: 1
Bytes: 9.4E+08 -- x: 0.9, y: 1
Bytes: 9.45E+08 -- x: 0.9, y: 1
Bytes: 9.5E+08 -- x: 0.9, y: 1
Bytes: 9.55E+08 -- x: 0.9, y: 1
Bytes: 9.6E+08 -- x: 0.9, y: 1
Bytes: 9.65E+08 -- x: 0.9, y: 1
Bytes: 9.7E+08 -- x: 0.9, y: 1
Bytes: 9.75E+08 -- x: 0.9, y: 1
Bytes: 9.8E+08 -- x: 0.9, y: 1
Bytes: 9.85E+08 -- x: 0.9, y: 1
Bytes: 9.9E+08 -- x: 0.9, y: 1
Bytes: 9.95E+08 -- x: 0.95, y: 1
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Sean Sailer Avatar answered Sep 27 '22 20:09

Sean Sailer
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