MUL24(3clc)

✨ MUL24 (3clc) ✨

okay bestie, gather round, because today we're talking about a little OpenCL function from the OpenCL Manual that is lowkey iconic and highkey a whole performance cheat code. it's called mul24 and it's giving "I do one thing and I do it fast." 💅

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🌸 NAME 🌸

mul24 — a fast integer function that multiplies 24-bit integer values. that's it. that's the whole job description. no cap. 🎀

gentype mul24(gentype x, gentype y);

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🦋 DESCRIPTION 🦋

so here's the tea. mul24 multiplies two 24-bit integer values, x and y. ✨

but wait, plot twist: x and y are actually 32-bit integers — they're just out here only using their low 24 bits to do the multiplication. the rest of those bits? not invited to the party. 🙈

now for the vibe check that matters, because this is where people get humbled:

mul24 should only be used when the values in x and y are in the range [-2^23, 2^23-1] if x and y are signed integers, and in the range [0, 2^24-1] if x and y are unsigned integers. if x and y are not in this range, the multiplication result is implementation-defined. 💀

so like, stay in your lane, stay in the range, and everything slays. step outside it and you're in undefined-behaviour-adjacent territory where nobody can promise you anything. fr fr.

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🌈 NOTES 🌈

fast integer functions can be used for optimizing performance of kernels. that's the whole point of them existing, bestie — speed. 🔥

and we use the generic type name gentype to indicate that the function can take int, int2, int3, int4, int8, int16, uint, uint2, uint3, uint4, uint8, or uint16 as the type for the arguments. so many options, all of them valid, all of them eating. 👑

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⭐ SPECIFICATION ⭐

OpenCL Specification[1]

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💜 SEE ALSO 💜

• integerFunctions(3clc) — go read the whole squad, iykyk 🫶

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👑 AUTHORS 👑

The Khronos Group

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🎀 COPYRIGHT 🎀

Copyright © 2007-2011 The Khronos Group Inc.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and/or associated documentation files (the "Materials"), to deal in the Materials without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Materials, and to permit persons to whom the Materials are furnished to do so, subject to the condition that this copyright notice and permission notice shall be included in all copies or substantial portions of the Materials.

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🍓 NOTES (the footnote one, not the other one) 🍓

1. OpenCL Specification — page 256, section 6.12.3 - Integer Functions. yes, it's a real page, go look. 📖

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okay that's the whole page, bestie, you're officially educated on mul24. 🧚 go forth and multiply (24 bits at a time, within the documented range, please and thank you). this little gift was brought to you by The Khronos Group, dated 01/14/2021, filed under MUL24(3clc) in the OpenCL Manual. mwah. 💖✨