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From: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
To: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Romain Naour <romain.naour@gmail.com>,
	Buildroot List <buildroot@buildroot.org>
Subject: Re: [Buildroot] [PATCH] utils/genrandconfig: reduce the maximum "size" of random configurations
Date: Sun, 14 Nov 2021 14:00:55 +0100	[thread overview]
Message-ID: <20211114140055.61997bd6@windsurf> (raw)
In-Reply-To: <20211113180206.GT247986@scaer>

Hello,

On Sat, 13 Nov 2021 19:02:06 +0100
"Yann E. MORIN" <yann.morin.1998@free.fr> wrote:

> On IRC, we discussed about using a normal distrobution rather than the
> uniform distribution that randint() provides.

Yeah, but after thinking more about it, I'm wondering whether this
makes sense or not. Indeed, why are we more interested by
configurations having ~10% of options enabled compared to the ones
having 1% or 20% ? All of them are equally interesting, aren't they?

> And here is the (10,7) gaussian (which has my preference):
> 
>      1: ###############    3%
>      2: #################    3%
>      3: ####################    4%
>      4: #######################    4%
>      5: #########################    5%
>      6: ###########################    5%
>      7: #############################    5%
>      8: ##############################    6%
>      9: ###############################    6%
>     10: ###############################    6%
>     11: ##############################    6%
>     12: #############################    5%
>     13: ###########################    5%
>     14: #########################    5%
>     15: #######################    4%
>     16: ####################    4%
>     17: #################    3%
>     18: ###############    3%
>     19: ############    2%
>     20: ##########    2%
>     21: ########    1%
>     22: ######    1%
>     23: ####    0%
>     24: ###    0%
>     25: ##    0%
>     26: #    0%
>     27: #    0%

I think the reality of Buildroot configurations is probably even more
biased towards having just a few percents of options enabled.

> Since a gaussian can output values all over ℝ, we must limit the range
> explicitly (note that the 0% above are not representing 0 occurences!):
> 
>     proba = 0
>     while proba < 1 or proba > 100:
>         proba = int(random.gauss(15, 5))

How much CPU is this loop going to consume before it gives a value that
is within 1 and 100 ? Would a % 100 be better ?

Best regards,

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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  reply	other threads:[~2021-11-14 13:01 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-13 14:17 [Buildroot] [PATCH] utils/genrandconfig: reduce the maximum "size" of random configurations Thomas Petazzoni
2021-11-13 18:02 ` Yann E. MORIN
2021-11-14 13:00   ` Thomas Petazzoni [this message]
2021-11-14 18:35     ` Yann E. MORIN
2021-11-14 12:48 ` Peter Korsgaard
2021-11-14 13:01   ` Thomas Petazzoni
2021-11-17 22:15   ` Peter Korsgaard

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