SIGNBIT(3clc)

🦋 SIGNBIT(3clc) — the OpenCL Manual ✨

okay bestie, welcome to the signbit page from the OpenCL Manual — she's short, she's sweet, she's literally just checking a bit for you 💅

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✨ NAME ✨

signbit — Test for sign bit. that's it. that's the whole job. 🎀

and here's the whole squad of signatures, verbatim, no cap:

int signbit(float );

intn signbit(floatn );

int signbit(double );

longn signbit(doublen );

int signbit (half)      // if half
extension enabled

shortn signbit (halfn)      // if half
extension enabled

like yes, there are six of them and two of them only show up if the half extension is enabled — read the little comment, it's right there, i'm not making this up 🫶

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🌸 DESCRIPTION 🌸

The built-in function signbit tests for the sign bit. that's the vibe check. 👑

The scalar version of the function returns a 1 if the sign bit in the float is set, else it returns 0. simple. iconic. no drama.

The vector version of the function returns the following for each component in floatn: -1 (i.e. all bits set) if the sign bit in the float is set, else it returns 0. so like... it does the same thing but per-lane and the true value is all-bits-set instead of just 1. the way that vector types do the absolute most 😭

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💜 NOTES 💜

okay important stuff, don't scroll past this, bestie:

• If an implementation extends this specification to support IEEE-754 flags or exceptions, then all built-in relational functions shall proceed without raising the invalid floating-point exception when one or more of the operands are NaNs. yes really. NaN girlies stay unbothered, no exception gets thrown. ✨
• The built-in relational functions are extended with cl_khr_fp16(3clc) to include appropriate versions of functions that take half, and half{2|3|4|8|16} as arguments and return values. that's the fp16 glow-up. 🌈
• The function returns a 0 if the specified relation is false and a 1 if the specified relation is true for scalar argument types. These functions shall return a 0 if the specified relation is false and a - 1 (i.e. all bits set) if the specified relation is true for vector argument types. scalar gets a lil 1, vector gets the whole all-bits-set situation. that's just how she is. 💅

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🎀 SPECIFICATION 🎀

OpenCL Specification[1] — go read it, it's giving authority 📚

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🔥 SEE ALSO 🔥

• relationalFunctions(3clc) — the friend group this one runs with 🫶

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👑 AUTHORS 👑

The Khronos Group. kings, honestly. 💖

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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 🌟

1. OpenCL Specification — page 264, section 6.12.6 - Relational Functions 📖

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okay so that's the whole page, bestie, you ate that. and for the cute sign-off: this lil masterpiece is brought to you by The Khronos Group, dated 01/14/2021, filed under SIGNBIT(3clc) — periodt. 💅✨🎀