dispatch_benchmark(3)

💖 dispatch_benchmark — the vibe check for your code's speed 💖

okay so bestie, we're in the dispatch_benchmark(3) page from the Library Functions Manual 🌸 and it's literally just here to tell you how fast your blocks are running. no cap.

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✨ NAME ✨

dispatch_benchmark — Measures block execution time ⏱️

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🎀 SYNOPSIS 🎀

#include <dispatch/dispatch.h>

uint64_t
dispatch_benchmark(size_t count, void (^block)(void));

uint64_t
dispatch_benchmark_f(size_t count, void *context,
    void (*function)(void *));

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💅 DESCRIPTION 💅

so the dispatch_benchmark() function takes your block and runs it over and over — however many times count says — and then hands you back the average number of nanoseconds per execution. that's it, that's the whole gig 🫶

this one is for debugging and performance analysis work. like, it's giving lab coat energy, not production energy, yk?

for the best results, pass a high count value to dispatch_benchmark(). lowkey obvious but they said it so we're saying it ✨

now, when you're benchmarking concurrent code, here's the tea 🍵:

• compare the serial version of the code against the concurrent version
• compare the concurrent version on different classes of hardware
• look for inflection points with various data sets

and keep these facts in mind, periodt:

• Code bound by computational bandwidth may be inferred by proportional changes in performance as concurrency is increased. 📈
• Code bound by memory bandwidth may be inferred by negligible changes in performance as concurrency is increased. 😐
• Code bound by critical sections may be inferred by retrograde changes in performance as concurrency is increased. 📉
  • Intentional: locks, mutexes, and condition variables. 🔒
  • Accidental: unrelated and frequently modified data on the same cache-line. 💀

bestie. the accidental one is the one that gets you. same cache-line, unrelated data, constantly getting touched?? that's not a bug, that's a crime scene 🙈

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🌈 RETURN VALUE 🌈

The dispatch_benchmark() function returns the average number of nanoseconds the given block takes to execute. that's your number, that's your truth, go off 👑

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👀 SEE ALSO 👀

• dispatch(3)

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and that's the whole page, babe 🦋 it's from Darwin, dated May 1, 2009 — yeah, 2009, this one's been iconic since before some of us could read 💜 stay fast, stay benchmarked, mwah 💋