If I execute 3*0.1, Julia prints the value as 0.30000000000000004. I believe the inaccuracy is caused by machine precision, but it doesn’t seem useful to me that Julia would display this. I also note that I have never encountered this kind of issue working with numbers greater than 1. What’s the cau…

Have you seen http://0.30000000000000004.com/ ? [image] aahaselgrove: Eg. (in C, what I would expect) That seems to print 2.9999999999999999e-01 (which Julia also does with @printf): julia> using Printf julia> @printf "%1.16e\n" .3 2.9999999999999999e-01 Anyway, Julia uses the GRISU (or Ry…

[image] aahaselgrove: but it doesn’t seem useful to me that Julia would display this. It is hard for Julia to know that you don’t want the result printed as accurately as possible. You can use the round function if you want to show fewer digits of precision. There is also the PR https://githu…

Well round does only work raliable in the windows built, see this thread

This was written in the context of “I only want to see a few digits and I don’t care about exact accuracy”.

I’d question the definition of exact accuracy - clearly, the exact solution is 0.3. Also, 0.4 cannot be represented exactly, but (0.1 + 0.1 + 0.1) + 0.1 produces 0.4. Not quite sure where the 4e-16 has gone, as I would have assumed numerical inaccuracies would compound.

[image] aahaselgrove: I’d question the definition of exact accuracy - clearly, the exact solution is 0.3. Please read through PSA: floating-point arithmetic and see if you have further questions.

I find it weird that executing 3/10 prints 0.3 but executing 3 * 0.1 prints 0.30000000000000004.

I understand how floating-point arithmetic works. The examples given there demonstrate catastrophic cancellation, and the result of all the calculations is equal to eps(). The article gives this example to demonstrate that all these calculations are performed in the same way. However, the examples w…

[image] aahaselgrove: I understand how floating-point arithmetic works. Are you sure? Cf [image] aahaselgrove: Eg. (in C, what I would expect) printf("%1.16e\n", .3); 3.0000000000000004 which is incorrect. [image] aahaselgrove: However, the examples which I am demonstrating can’…

[image] kristoffer.carlsson: That seems to print 2.9999999999999999e-01 (which Julia also does with @printf ): Must have missed a compile, that put me off track >.<. [image] kristoffer.carlsson: Anyway, Julia uses the GRISU (or Ryu) algorithm to print the float. It guarantees that the ge…

Working with machine precision

General Usage

kristoffer.carlsson October 7, 2019, 8:25am 6

Please read through PSA: floating-point arithmetic and see if you have further questions.

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Working with machine precision

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