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---
title: "@rianflo Explicit packed 16-bit code. FSR1 example: https://github.com/GPUOpen-E"
author: "NOTimothyLottes"
handle: "@NOTimothyLottes"
post_url: "https://x.com/NOTimothyLottes/status/1597798161665253376"
post_id: "1597798161665253376"
timestamp: "2022-11-30 03:42:22"
post_count: 7
reply_count: 0
repost_count: 0
like_count: 1
view_count: 0
---

# @NOTimothyLottes — @rianflo Explicit packed 16-bit code. FSR1 example: https://github.com/GPUOpen-E

## Post 1 (2022-11-29 18:38:24)

"The road to 16-bit floats GPU is paved with our blood"
:-/

https://www.yosoygames.com.ar/wp/2022/01/the-road-to-16-bit-floats-gpu-is-paved-with-our-blood/

## Post 2 (2022-11-29 22:19:53) — reply to Post 1

@rianflo Explicit packed 16-bit works on AMD Vulkan Vega and up. I typically get up to 30% improvement on ALU bound stuff. Lots of occupancy wins. I don't use {HLSL, RenderDoc, Reflection, RADV, or VS/PS}. All constants are packed and aliased as UINT, so no coversion overheads.

## Post 3 (2022-11-29 22:24:24) — reply to Post 2

@NOTimothyLottes Oh I know the benefits. Just no simple clear way to write it in GLSL for vulkan.

## Post 4 (2022-11-29 22:26:03) — reply to Post 3

@rianflo Sure there is. CAS/FSR1/etc all shipped with fantastic GLSL versions using 16-bit packed math (I wrote those), all which at the time got fantastic code generation using AMD's drivers.

## Post 5 (2022-11-29 22:32:10) — reply to Post 4

@NOTimothyLottes What GLSL extension did you use?

## Post 6 (2022-11-29 22:33:35) — reply to Post 5

@NOTimothyLottes Oh wait, you're saying you wrote the fp16 math manually?

## Post 7 (2022-11-30 03:42:22) — reply to Post 6

@rianflo Explicit packed 16-bit code. FSR1 example: https://github.com/GPUOpen-Effects/FidelityFX-FSR/blob/master/ffx-fsr/ffx_fsr1.h - There are different 'F' (32-bit) and 'H' and 'Hx2' (packed 16-bit) functions.