From: "Valdis Klētnieks" <valdis.kletnieks@vt.edu>
To: Ruben Safir <ruben@mrbrklyn.com>
Cc: kernelnewbies@kernelnewbies.org
Subject: Re: Do I need strong mathematical bases to work in the memory subsystem?
Date: Thu, 03 Oct 2019 12:51:44 -0400 [thread overview]
Message-ID: <71184.1570121504@turing-police> (raw)
In-Reply-To: <7374125a-646f-7057-347b-f17ef51e9865@mrbrklyn.com>
[-- Attachment #1.1: Type: text/plain, Size: 1852 bytes --]
On Thu, 03 Oct 2019 06:55:50 -0400, Ruben Safir said:
> I wouldn't call that C code basic. Regardless, showing an example of a
> driver that doesn't need math, and it might if you understood the high
> level math, and your not aware of it, but predictive branching would
> need it.
See the kernel code that maintains statistical data on likely()/unlikely()
under CONFIG_PROFILE_ANNOTATED_BRANCHES. Seems like "this likely() actually
only triggers 3% of the time" isn't exactly higher math.
There may be some magic going on in the chip hardware - but that's in the
*hardware* and inaccessible to the programmer. I'll also point out that
speculative execution has *other* problems.....
> You can not calculate simple interest efficiently without calculus.
Simple interest is *easy*. Amount * percent. Done. It's compound interest
that only sort of needs calculus (and there only to understand the limiting
case) - and even there I doubt any banks actually use calculus, just apply the
iterative approach.
// yearly interest compounded monthly
for (i=0;i<num_months;i++) { balance += (balance * percent) /12;}
I'd like to see you do it more efficiently using calculus. Especially if you
have to take into account rounding to the nearest penny 36 times for a 3
year loan. That stuff is why COBOL is still around. :)
> calculus. This repeadely ends up being an issue of "if I don't know it,
> I don't need it", which is wrong. More math helps you every time. Math
Somehow I doubt that the Taniyama-Shimura-Weil conjecture is ever
going to have any relevance inside the kernel.
> is advanced logic. I can't tell you how many times I see folks brute
> force their way to solutions that they should be using integration.
Can you show an example of where the kernel needs to be using integration?
[-- Attachment #1.2: Type: application/pgp-signature, Size: 832 bytes --]
[-- Attachment #2: Type: text/plain, Size: 170 bytes --]
_______________________________________________
Kernelnewbies mailing list
Kernelnewbies@kernelnewbies.org
https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
next prev parent reply other threads:[~2019-10-03 16:52 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-29 22:48 Do I need strong mathematical bases to work in the memory subsystem? CRISTIAN ANDRES VARGAS GONZALEZ
2019-09-30 5:06 ` Valdis Klētnieks
2019-10-03 1:47 ` Ruben Safir
2019-10-03 3:35 ` Valdis Klētnieks
2019-10-03 3:42 ` Ruben Safir
2019-10-03 7:00 ` Greg KH
2019-10-03 10:55 ` Ruben Safir
2019-10-03 16:51 ` Valdis Klētnieks [this message]
2019-10-03 17:21 ` Sahil Gupta
2019-10-06 1:49 ` Grant Taylor
2019-10-16 15:18 ` Cindy Sue Causey
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=71184.1570121504@turing-police \
--to=valdis.kletnieks@vt.edu \
--cc=kernelnewbies@kernelnewbies.org \
--cc=ruben@mrbrklyn.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).