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bremac

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Correctly-rounded evaluation of a function: why, how, and at what cost? [pdf]

hal.science
2 points·by bremac·2 yıl önce·0 comments

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bremac
·geçen yıl·discuss
Location: San Francisco, CA

Remote: Yes

Willing to relocate: Yes

Technologies: Java, C, C++, SQL, Python, Kubernetes, Linux, perf, PostgreSQL, OCaml

Résumé/CV: http://macdonell.net/resume.pdf

Email: [email protected]

Staff engineer with over a decade of experience leading products to successful delivery and beyond. Recently focused on high-performance streaming analytics at Sight Machine (I led the design and implementation of their stream processing engine, and before that, their data acquisition product), I can also work as a generalist backend developer or team lead.

Shoot me an email if you want to chat!
bremac
·2 yıl önce·discuss


  Location: San Francisco, CA
  Remote: Yes
  Willing to relocate: Yes
  Technologies: Java, C, C++, SQL, Python, Kubernetes, Linux, perf, PostgreSQL, OCaml
  Résumé/CV: http://macdonell.net/resume.pdf
  Email: [email protected]
Staff engineer with over a decade of experience leading products to successful delivery and beyond. Recently focused on high-performance streaming analytics at Sight Machine (I led the design and implementation of their stream processing product, and before that, their data acquisition product), I can also work as a generalist backend developer or team lead.

Shoot me an email if you want to chat.

No management positions, please!
bremac
·2 yıl önce·discuss
Unfortunately none of the hardware used for testing supports FP16 arithmetic. Between Intel and AMD, the only platform that supports AVX512-FP16 is currently Sapphire Rapids.
bremac
·2 yıl önce·discuss
Value types still require allocation for types larger than 128 bits if the value is either nullable or atomic — that seems like a reasonable trade-off to me.
bremac
·2 yıl önce·discuss
Keep in mind that you still need send a print job to the fake printer to trigger the exploit. If you send the job to your real printer, nothing happens.
bremac
·2 yıl önce·discuss
Per the bug report, all versions since Java 8 are affected.
bremac
·2 yıl önce·discuss
Unfortunately, unless the JIT can prove that the address you are accessing via the segment is non-negative, it can't elide the bounds check. See https://mail.openjdk.org/pipermail/panama-dev/2023-July/0194... for a bit more information.
bremac
·2 yıl önce·discuss
As the comment you replied to indicates, both of those APIs perform bounds-checking. In certain tight loops, this can add up to quite a bit of overhead [1]. However, it's not documented, but if you really know what you are doing you can convince the JIT to elide the bounds checks for MemorySegments [2].

[1] https://mail.openjdk.org/pipermail/panama-dev/2023-July/0193...

[2] https://mail.openjdk.org/pipermail/panama-dev/2023-July/0194...
bremac
·3 yıl önce·discuss
Reading between the lines, it sounds as if they're using mmap. There is no "append" operation on a memory mapping, so the file would need to be preallocated before mapping it.

If the preallocation is done using fallocate or just writing zeros, then by default it's backed by blocks on disk, and readahead must hit the disk since there is data there. On the other hand, preallocating with fallocate using FALLOC_FL_ZERO_RANGE or (often) with ftruncate() will just update the logical file length, and even if readahead is triggered it won't actually hit the disk.