sys/div: calculate magic numbers at compile time#9280
sys/div: calculate magic numbers at compile time#9280ZetaR60 wants to merge 12 commits intoRIOT-OS:masterfrom
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I have been tinkering with this a bit, and I cannot get it to come out exactly like what unittests expects. I was hoping that this wouldn't force me to implement floats, but there may be a loss in precision due to the general nature of the calculation method. |
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Interesting improvement. Did you compare the computed inverses against the old hard coded magic numbers? |
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Now tested and working properly via tests/unittests (tests-div). Comparison between the magic numbers (the new ones are a single bitshift from the old): Test results: |
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@ZetaR60 perhaps we can combine the frac and div modules and get the performance of div and the runtime configurable constants of frac? |
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@gebart How are you considering doing this combination? Is div still clearly better than frac when frac is used with constant parameters? I rewrote div primarily because I am working on adding multiple timer support (including RTT/RTC) to xtimer, and it is difficult to convert clocks when things are not all hard-coded. This is still very WIP, but I can create a PR early for it so that it is easier to discuss what the requirements are for clock conversion moving forward. |
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@gebart What do you think about the best way to interface something like #9308 with div or frac? When writing a function to convert ticks to us the most straightforward way is to have |
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@ZetaR60 for runtime configurable frequencies I would just add a static frac_t inside the module, or a frac_t member in the params struct. |
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Type: enhancement
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This is a rewrite of sys/div to provide much simpler division by calculating the required magic numbers at compile time, rather than hard-coding them.
tests/unittests/tests-div is partially working, with a few rounding errors that I need to fix: