JuliaDynamics/DrWatson.jl

Inconsistent rounding for parameters in savename

Open

#350 opened on Jun 27, 2022

View on GitHub
 (3 comments) (1 reaction) (0 assignees)Julia (915 stars) (94 forks)batch import
buggood first issue

Description

When using savename, some unexpected behaviour can happen when using some parameter values with the sigdigits keyword. This seems to be due to the fact that savename uses the round function to format numbers, which is designed for outputting numbers as strings. One issue occurs when using very small or large numbers, and is due to a known bug in round, but is machine specific.

For example,

julia> savename("test", (p1=3.6e-23,), sigdigits=1)
"test_p1=4.0000000000000004e-23"

but for one order of magnitude larger

julia> savename("test", (p1=3.6e-22,), sigdigits=1)
"test_p1=4e-22"

Additionally, while it may round the correct number of significant digits, the output will not necessarily represent the specified number of significant digits. Specifically, this occurs when there should be additional zeros, which are either not be added to the given number, or are dropped when the number rounds to something that can be represented with fewer digits. For example,

julia> savename("test", (p1=3.5e-6,), sigdigits=4)
"test_p1=3.5e-6"
julia> savename("test", (p1=3.4999e-6,), sigdigits=4)
"test_p1=3.5e-6"

It would probably be more robust to use string formatting methods, for example the Printf.@sprintf macro, to produce the final string after using the round function.

I am using DrWatson v2.9.1 and julia version 1.7.3.

Contributor guide

Tech stack
None
Domain
data
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Basic Julia programmingUnderstanding of floating point arithmeticFamiliarity with DrWatson's savename function
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70
Research direction
The issue outlines a bug in the `savename` function where rounding using `round` leads to inconsistent significant digits. The proposed fix is to use `Printf.@sprintf` for string formatting. The contributor should locate the `savename` function implementation in the DrWatson source code (likely in `src/savename.jl`), identify where `round` is applied, and replace it with appropriate `Printf` formatting. Ensure to handle edge cases such as very small/large numbers and trailing zeros. After implementing, run the existing test suite and add new tests to cover the reported cases. The issue includes examples that can be used as test cases.