From: "Dr. Philipp Tomsich" <philipp.tomsich@theobroma-systems.com>
To: "Kumar, Venkataramanan" <Venkataramanan.Kumar@amd.com>
Cc: Benedikt Huber <benedikt.huber@theobroma-systems.com>,
"pinskia@gmail.com" <pinskia@gmail.com>,
"gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] [aarch64] Implemented reciprocal square root (rsqrt) estimation in -ffast-math
Date: Thu, 25 Jun 2015 15:52:00 -0000 [thread overview]
Message-ID: <1E4680F0-02C8-4999-958C-8B531BC850DA@theobroma-systems.com> (raw)
In-Reply-To: <7794A52CE4D579448B959EED7DD0A4723DD10430@satlexdag06.amd.com>
Kumar,
what is the relative gain that you see on Cortex-A57?
Thanks,
Philipp.
> On 25 Jun 2015, at 17:35, Kumar, Venkataramanan <Venkataramanan.Kumar@amd.com> wrote:
>
> Changing to "1 step for float" and "2 steps for double" gives better gains now for gromacs on cortex-a57.
>
> Regards,
> Venkat.
>> -----Original Message-----
>> From: gcc-patches-owner@gcc.gnu.org [mailto:gcc-patches-
>> owner@gcc.gnu.org] On Behalf Of Benedikt Huber
>> Sent: Thursday, June 25, 2015 4:09 PM
>> To: pinskia@gmail.com
>> Cc: gcc-patches@gcc.gnu.org; philipp.tomsich@theobroma-systems.com
>> Subject: Re: [PATCH] [aarch64] Implemented reciprocal square root (rsqrt)
>> estimation in -ffast-math
>>
>> Andrew,
>>
>>> This is NOT a win on thunderX at least for single precision because you have
>> to do the divide and sqrt in the same time as it takes 5 multiples (estimate
>> and step are multiplies in the thunderX pipeline). Doubles is 10 multiplies
>> which is just the same as what the patch does (but it is really slightly less than
>> 10, I rounded up). So in the end this is NOT a win at all for thunderX unless
>> we do one less step for both single and double.
>>
>> Yes, the expected benefit from rsqrt estimation is implementation specific. If
>> one has a better initial rsqrte or an application that can trade precision for
>> execution time, we could offer a command line option to do only 2 steps for
>> doulbe and 1 step for float; similar to -mrecip-precision for PowerPC.
>> What are your thoughts on that?
>>
>> Best regards,
>> Benedikt
next prev parent reply other threads:[~2015-06-25 15:43 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-18 11:57 Benedikt Huber
2015-06-18 12:03 ` [PATCH] 2015-06-15 Benedikt Huber <benedikt.huber@theobroma-systems.com> Benedikt Huber
2015-06-27 8:12 ` Andrew Pinski
2015-06-18 12:36 ` [PATCH] [aarch64] Implemented reciprocal square root (rsqrt) estimation in -ffast-math Kumar, Venkataramanan
2015-06-24 16:49 ` Evandro Menezes
2015-06-24 16:55 ` Dr. Philipp Tomsich
2015-06-24 17:16 ` Benedikt Huber
2015-06-24 18:37 ` Evandro Menezes
2015-06-24 20:11 ` Dr. Philipp Tomsich
2015-06-24 20:54 ` Evandro Menezes
2015-06-25 11:52 ` Benedikt Huber
2015-06-25 7:01 ` Kumar, Venkataramanan
2015-06-25 7:03 ` pinskia
2015-06-25 9:43 ` Ramana Radhakrishnan
2015-06-27 2:01 ` Andrew Pinski
2015-06-25 11:07 ` Benedikt Huber
2015-06-25 13:27 ` Michael Matz
2015-06-25 15:43 ` Kumar, Venkataramanan
2015-06-25 15:52 ` Dr. Philipp Tomsich [this message]
2015-06-25 16:47 ` Kumar, Venkataramanan
2015-06-28 15:13 ` pinskia
2015-06-29 8:30 ` Kumar, Venkataramanan
2015-06-29 9:07 ` Dr. Philipp Tomsich
2015-06-29 9:22 ` Kumar, Venkataramanan
2015-06-29 11:44 ` James Greenhalgh
2015-06-29 11:56 ` Dr. Philipp Tomsich
2015-06-29 16:57 ` pinskia
2015-06-29 19:07 ` Kumar, Venkataramanan
2015-07-14 22:26 ` Evandro Menezes
2015-07-20 9:46 ` Kumar, Venkataramanan
2015-07-20 15:58 ` Evandro Menezes
2015-07-13 19:09 ` Evandro Menezes
2015-07-14 22:20 ` Evandro Menezes
2015-06-29 14:20 ` Benedikt Huber
2015-06-29 17:35 ` Benedikt Huber
2015-06-29 17:44 ` Kumar, Venkataramanan
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=1E4680F0-02C8-4999-958C-8B531BC850DA@theobroma-systems.com \
--to=philipp.tomsich@theobroma-systems.com \
--cc=Venkataramanan.Kumar@amd.com \
--cc=benedikt.huber@theobroma-systems.com \
--cc=gcc-patches@gcc.gnu.org \
--cc=pinskia@gmail.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 read-only IMAP folder(s) and NNTP newsgroup(s).