Floor and Ceil versus Denormals on CPU and GPU
The article discusses the behavior of floating-point numbers, particularly focusing on the functions floor, ceil, trunc, and round. It highlights the differences in handling subnormal numbers, also known as denormals, across various platforms. The author shares insights from tests conducted on CPU and GPU architectures regarding the preservation of denormals during these operations.
- ▪The floor function rounds down towards negative infinity, while ceil rounds up towards positive infinity.
- ▪Subnormal numbers are represented differently in floating-point formats, affecting how they are processed on different platforms.
- ▪The handling of denormals can lead to significant differences in results, especially when applying rounding functions.
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| Original publisher | Asawicki |
| Canonical URL | https://asawicki.info/news_1802_floor_and_ceil_versus_denormals_on_cpu_and_gpu |
| Publication time | Tue, 26 May 2026 13:22:13 +0000 |
| Retrieval time | 2026-05-26T13:37:49.521Z |
| Last seen | 2026-05-26T13:37:49.521Z |
| Headline source | Publisher (no WeSearch rewrite) |
| Excerpt source | publisher body |
| Excerpt method | First ~120 words (~800 chars) of extracted publisher body, fair-use limited. |
| Summary | WeSearch · cerebras-chat (WeSearch summarizer) |
| Summary source text | contentText |
| Citation coverage | Summary is a WeSearch-generated derivative; primary citation is the original publisher URL. |
| Cluster | _rgZonZdM6xj |
| Cluster logic | Grouped by semantic title/content similarity across sources within a rolling window. Same-publisher template collisions are excluded from coverage comparison. |
| Ranking reason | Story pages are not engagement-ranked. Hub feeds use recency, with optional source-diversified chronological ordering (cap consecutive stories per source). No personalized ranking. |
| Publisher visit | Yes — open original |
| Substitutes article? | No — link-out required for full text |
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| Indexing | May the item be indexed (stored, ranked, made findable)? | Allowed |
| Snippet | May a short excerpt of the publisher's text be shown? | Allowed |
| AI summary | May WeSearch generate its own short summary of the article? | Limited |
| Retrieval / RAG | May the content be exposed for third-party retrieval-augmented generation? | Not asserted |
| Model training | May the content be used to train AI models? | Not asserted |
| Commercial reuse | May the content be reused commercially? | Not permitted |
Basis: Derived from the published RSS/Atom feed. Contact: [email protected]. Reviewed: 2026-07-24.
Opening excerpt (first ~120 words) tap to expand
Sat 23 May 2026 Recently, I dove deep into floating-point numbers and their behavior. Somehow, this topic haunts me in my programming practice since I created Floating-Point Formats Cheatsheet back in 2013 and also released a comprehensive article The Secrets of Floating-Point Numbers in 2024. This time, I would like to focus on one specific question: What is the result of floor(-1.175493930432748e-38) ? Note: Hexadecimal value of our input number is 0x807FFFFD. Floor, ceil, trunc, round To recap, floor, ceil, trunc, round are functions available in the standard library of C, C++, as well as shading languages: HLSL and GLSL. Each of them transforms a floating-point number into an integral floating-point value, but using different rounding rules.
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Excerpt limited to ~120 words for fair-use compliance. The full article is at Asawicki.
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