Enhance precision and safety in time calculations #54
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Introduce a new inline function mult_frac() to compute "x * n / d" with enhanced precision and safety. This function addresses the common issues of overflow and loss of precision that can occur with straightforward approaches to this calculation. Directly computing "x * n / d" can lead to problems: - Performing the division first can result in loss of precision due to integer truncation. - Performing multiplication before division can risk overflow. The mult_frac() function mitigates these issues by: 1. Calculating the quotient and remainder of 'x' divided by 'd'. 2. Using these intermediate results to perform the final calculation, thus avoiding intermediate overflow and preserving precision. This approach is based on the Linux kernel's mult_frac() macro [1], which follows a similar method to handle these calculations robustly. Link: https://elixir.bootlin.com/linux/v6.10.7/source/include/linux/math.h#L121 [1]
Enhance the semu_timer_clocksource() function by utilizing the mult_frac() function to improve the precision of converting time to clock ticks. This update refines the calculations for converting time derived from clock_gettime() and mach_absolute_time() into clock ticks. This ensures that the time-to-clock-ticks conversion is more reliable and precise, addressing potential precision issues effectively.
|
Thank @visitorckw for contributing! |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Introduces a new inline function, mult_frac(), to handle fractional multiplication with improved precision and safety by computing x * n / d while avoiding common issues like overflow and precision loss. Additionally, the semu_timer_clocksource() function has been refactored to use mult_frac() for time-related calculations, including the calculations for converting time derived from clock_gettime() and mach_absolute_time() into clock ticks. These updates collectively enhance the accuracy and reliability of time computations throughout the codebase.