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Created on 2021-12-21 06:59 by joshinsel, last changed 2022-04-11 14:59 by admin. This issue is now closed.
| Messages (3) | |||
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| msg408986 - (view) | Author: Joshua Insel (joshinsel) | Date: 2021-12-21 06:59 | |
math.log(536870912, 2) should return 29.0, because 2^29 = 536870912. However, it instead returns 29.000000000000004. |
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| msg408988 - (view) | Author: Joshua Insel (joshinsel) | Date: 2021-12-21 07:20 | |
The same problem occurs with the log function from the C standard library, which Python uses to implement its same-named function. |
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| msg408992 - (view) | Author: Mark Dickinson (mark.dickinson) *  |
Date: 2021-12-21 08:54 | |
Yes, confirmed that this is not a bug, but just one of the many consequences of approximating real numbers by floating-point numbers. You may be interested in math.log2 and/or int.bit_length. math.log2(x) *may* give you more accurate results than math.log(x, 2) when x is a power of two, but there are no guarantees - we're at the mercy of the C math library here. |
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| History | |||
|---|---|---|---|
| Date | User | Action | Args |
| 2022-04-11 14:59:53 | admin | set | github: 90302 |
| 2021-12-21 08:54:04 | mark.dickinson | set | resolution: not a bug messages: + msg408992 nosy: + mark.dickinson |
| 2021-12-21 07:20:48 | joshinsel | set | status: open -> closed messages: + msg408988 stage: resolved |
| 2021-12-21 06:59:34 | joshinsel | create | |