R devel - Sep 2021 - WISH: set.seed(seed) to produce error if length(seed) != 1 (now silent)

Hello,

A vector with a length >= 2 to set.seed would probably be a bug. An error
message will help the user to fix his R code. The bug may be accidental or due
to bad understanding of the set.seed function. For instance, a user may think
that the whole state of the PRNG can be passed to set.seed.

The "if" instruction, emits a warning when the condition has length
>= 2, because it is often a bug. I would expect a warning or error with
set.seed().

Validating inputs and emitting errors early is a good practice.

Just my 2 cents.

Sincerely.
Andre GILLIBERT

-----Message d'origine-----
De?: R-devel [mailto:r-devel-bounces at r-project.org] De la part de Avraham
Adler
Envoy??: vendredi 17 septembre 2021 12:07
??: Henrik Bengtsson
Cc?: R-devel
Objet?: Re: [Rd] WISH: set.seed(seed) to produce error if length(seed) != 1 (now
silent)

Hi, Henrik.

I?m curious, other than proper programming practice, why?

Avi

On Fri, Sep 17, 2021 at 11:48 AM Henrik Bengtsson <
henrik.bengtsson at gmail.com> wrote:
> Hi,
>
> according to help("set.seed"), argument 'seed' to
set.seed() should be:
>
>   a single value, interpreted as an integer, or NULL (see ?Details?).
>
> From code inspection (src/main/RNG.c) and testing, it turns out that
> if you pass a 'seed' with length greater than one, it silently uses
> seed[1], e.g.
>
> > set.seed(1); sum(.Random.seed)
> [1] 4070365163
> > set.seed(1:3); sum(.Random.seed)
> [1] 4070365163
> > set.seed(1:100); sum(.Random.seed)
> [1] 4070365163
>
> I'd like to suggest that set.seed() produces an error if length(seed)
> > 1.  As a reference, for length(seed) == 0, we get:
>
> > set.seed(integer(0))
> Error in set.seed(integer(0)) : supplied seed is not a valid integer
>
> /Henrik
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>
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> I?m curious, other than proper programming practice, why?
Life's too short for troubleshooting silent mistakes - mine or others.

While at it, searching the interwebs for use of set.seed(), gives
mistakes/misunderstandings like using set.seed(<double>), e.g.
> set.seed(6.1); sum(.Random.seed)
[1] 73930104
> set.seed(6.2); sum(.Random.seed)
[1] 73930104

which clearly is not what the user expected.  There are also a few
cases of set.seed(<character>), e.g.
> set.seed("42"); sum(.Random.seed)
[1] -2119381568
> set.seed(42); sum(.Random.seed)
[1] -2119381568

which works just because as.numeric("42") is used.

/Henrik

On Fri, Sep 17, 2021 at 12:55 PM GILLIBERT, Andre
<Andre.Gillibert at chu-rouen.fr> wrote:
>
> Hello,
>
> A vector with a length >= 2 to set.seed would probably be a bug. An
error message will help the user to fix his R code. The bug may be accidental or
due to bad understanding of the set.seed function. For instance, a user may
think that the whole state of the PRNG can be passed to set.seed.
>
> The "if" instruction, emits a warning when the condition has
length >= 2, because it is often a bug. I would expect a warning or error
with set.seed().
>
> Validating inputs and emitting errors early is a good practice.
>
> Just my 2 cents.
>
> Sincerely.
> Andre GILLIBERT
>
> -----Message d'origine-----
> De : R-devel [mailto:r-devel-bounces at r-project.org] De la part de
Avraham Adler
> Envoy? : vendredi 17 septembre 2021 12:07
> ? : Henrik Bengtsson
> Cc : R-devel
> Objet : Re: [Rd] WISH: set.seed(seed) to produce error if length(seed) != 1
(now silent)
>
> Hi, Henrik.
>
> I?m curious, other than proper programming practice, why?
>
> Avi
>
> On Fri, Sep 17, 2021 at 11:48 AM Henrik Bengtsson <
> henrik.bengtsson at gmail.com> wrote:
>
> > Hi,
> >
> > according to help("set.seed"), argument 'seed' to
set.seed() should be:
> >
> >   a single value, interpreted as an integer, or NULL (see ?Details?).
> >
> > From code inspection (src/main/RNG.c) and testing, it turns out that
> > if you pass a 'seed' with length greater than one, it silently
uses
> > seed[1], e.g.
> >
> > > set.seed(1); sum(.Random.seed)
> > [1] 4070365163
> > > set.seed(1:3); sum(.Random.seed)
> > [1] 4070365163
> > > set.seed(1:100); sum(.Random.seed)
> > [1] 4070365163
> >
> > I'd like to suggest that set.seed() produces an error if
length(seed)
> > > 1.  As a reference, for length(seed) == 0, we get:
> >
> > > set.seed(integer(0))
> > Error in set.seed(integer(0)) : supplied seed is not a valid integer
> >
> > /Henrik
> >
> > ______________________________________________
> > R-devel at r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-devel
> >
> --
> Sent from Gmail Mobile
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>