From: Stephen Hemminger <stephen@networkplumber.org>
To: "Mattias Rönnblom" <hofors@lysator.liu.se>
Cc: dev@dpdk.org, "Mattias Rönnblom" <mattias.ronnblom@ericsson.com>,
"Ray Kinsella" <mdr@ashroe.eu>
Subject: Re: [PATCH v4 1/3] random: add rte_drand() function
Date: Thu, 26 May 2022 08:28:05 -0700 [thread overview]
Message-ID: <20220526082805.333892a1@hermes.local> (raw)
In-Reply-To: <84afee2e-fa4c-faf1-d046-febb0ae77c09@lysator.liu.se>
On Thu, 26 May 2022 15:20:29 +0200
Mattias Rönnblom <hofors@lysator.liu.se> wrote:
> > +#else
> > + /* Slower method requiring floating point divide
> > + *
>
> Do you know how much slower? I ran rand_perf_test on two of my systems.
>
> AMD 5900X Pi4 (ARM Cortex-A72)
> IEEE754 version 12 1.19
> Non-IEEE754 version 11 1.16
> Naive version* 24 1.16
>
> * (double)rte_rand() / (double)UINT64_MAX
>
> Numbers are TSC cycles/op.
>
> Surprisingly, it seems like the IEEE754 version is slower on both of
> these machines.
>
> Do you have a machine (or a different use case) where the supposedly
> more optimized version actually runs faster?
The direct method is based off the concept used by glibc and others
and the divide (including spelling error) are from FreeBSD.
Be careful with micro benchmarks. A better one would be do
rte_drand() compared with something to check whether it is in range.
next prev parent reply other threads:[~2022-05-26 15:28 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-24 18:46 [RFT 0/2] pie: floating point fixes Stephen Hemminger
2022-05-24 18:46 ` [RFT 1/2] rte_pie: remove unnecessary floating point Stephen Hemminger
2022-05-24 18:46 ` [RFT 2/2] rte_pie: fix incorrect floating point math Stephen Hemminger
2022-05-24 19:31 ` [RFT 0/2] pie: floating point fixes Morten Brørup
2022-05-24 22:18 ` [RFT v2 0/3] pie: fix random number issues Stephen Hemminger
2022-05-24 22:18 ` [RFT v2 1/3] random: add rte_rand_float() Stephen Hemminger
2022-05-25 11:55 ` Ray Kinsella
2022-05-25 14:45 ` Mattias Rönnblom
2022-05-25 15:26 ` Morten Brørup
2022-05-25 15:45 ` Stephen Hemminger
2022-05-25 15:47 ` Stephen Hemminger
2022-05-24 22:18 ` [RFT v2 2/3] rte_pie: remove unnecessary floating point Stephen Hemminger
2022-05-24 22:18 ` [RFT v2 3/3] rte_pie: fix incorrect floating point math Stephen Hemminger
2022-05-25 17:12 ` [PATCH v3 0/3] introduce random floating point function Stephen Hemminger
2022-05-25 17:12 ` [PATCH v3 1/3] random: add rte_drand() funciton Stephen Hemminger
2022-05-25 17:12 ` [PATCH v3 2/3] rte_pie: remove unnecessary floating point Stephen Hemminger
2022-05-25 17:12 ` [PATCH v3 3/3] rte_pie: fix incorrect floating point math Stephen Hemminger
2022-05-25 20:31 ` [PATCH v4 0/3] introduce random floating point function Stephen Hemminger
2022-05-25 20:31 ` [PATCH v4 1/3] random: add rte_drand() function Stephen Hemminger
2022-05-26 9:56 ` Ray Kinsella
2022-05-26 13:20 ` Mattias Rönnblom
2022-05-26 15:25 ` Stephen Hemminger
2022-05-26 15:28 ` Stephen Hemminger [this message]
2022-05-26 20:19 ` Stephen Hemminger
2022-05-25 20:31 ` [PATCH v4 2/3] rte_pie: remove unnecessary floating point Stephen Hemminger
2022-05-25 20:31 ` [PATCH v4 3/3] rte_pie: fix incorrect floating point math Stephen Hemminger
2022-05-26 7:06 ` [PATCH v4 0/3] introduce random floating point function Morten Brørup
2022-05-26 20:26 ` [PATCH v5 " Stephen Hemminger
2022-05-26 20:26 ` [PATCH v5 1/3] random: add rte_drand() function Stephen Hemminger
2022-05-26 20:26 ` [PATCH v5 2/3] rte_pie: remove unnecessary floating point Stephen Hemminger
2022-05-30 11:50 ` Dumitrescu, Cristian
2022-06-21 8:18 ` Singh, Jasvinder
2022-05-26 20:26 ` [PATCH v5 3/3] rte_pie: fix incorrect floating point math Stephen Hemminger
2022-05-30 11:50 ` Dumitrescu, Cristian
2022-06-21 8:18 ` Singh, Jasvinder
2022-06-22 9:21 ` [PATCH v5 0/3] introduce random floating point function Thomas Monjalon
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