fixed_power_int(9)

💅 fixed_power_int — Kernel API Manual, section 9, bestie 💅

okay so this is fixed_power_int(9) straight out of the Kernel API Manual, and it's genuinely one of those little functions that ate and left no crumbs. it does one thing: raises x to the power n, in O(log n) time. that's the whole vibe. iykyk. 🎀

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✨ NAME ✨

fixed_power_int — compute: x^n, in O(log n) time. literally that's it, that's the function, and it's iconic for it. 💖

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🌸 SYNOPSIS 🌸

unsigned long fixed_power_int (unsigned long x , unsigned int frac_bits
, unsigned int n );

copy it exactly like that, spacing and all, don't come for me, that's the manpage's formatting not mine 🫶

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🦋 ARGUMENTS 🦋

• x — the base of the power. the main character of this whole operation ngl.
• frac_bits — fractional bits of x. yes it's a parameter, yes the description doesn't elaborate, no i will not be inventing lore about it 💀
• n — the power you're raising x to. the exponent. the moment.

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🔥 DESCRIPTION 🔥

okay so here's the slay. this function exploits the relationship between two things:

1. the definition of the natural power function, x^n := x*x*...*x — that is, x multiplied by itself for n times, the classic, the original, the "i could do this with a for loop" method, and
2. the binary encoding of numbers that computers actually use, n := n_i * 2^i, where n_i \lem {0, 1} is the binary vector representing n.

put those two together and you find:

x^n := x^( n_i * 2^i) := Prod x^(n_i * 2^i)

which is, in the manpage's own words, "of course trivially computable in O(log_2 n)" — the length of our binary vector. so instead of doing n multiplications like a peasant, you're doing logarithmically many, which is giving big brain energy fr fr. 🧚✨

ngl the original page really does say "of course trivially computable" like it's the most obvious thing in the world. and honestly? for her it is. 👑

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💜 SEE ALSO 💜

• Kernel file ./kernel/sched/loadavg.c
• get_avenrun(9)

go read those if you want the full lore, bestie, i'm just the messenger 🌈

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and that's the page!! 💅 this little beauty lives in ./kernel/sched and this version is dated October 2026, title fixed_power_int(9), in case you were wondering where it came from. k byeee, go compute some powers 🍓🦋💖