Re: Why compiler is able to vectorize on int but not on unsigned

From	Richard Heathfield <invalid@see.sig.invalid>
Organization	Go, ion artisan!
Subject	Re: Why compiler is able to vectorize on int but not on unsigned
Newsgroups	comp.lang.c++, comp.lang.c
References	<20141203111909.5ec8c7fc@maxa-pc> <m5n1l8$m45$1@dont-email.me> <m5n4rq$k42$1@speranza.aioe.org> <m5n6dk$8d0$1@dont-email.me>
Followup-To	Choose, an, appropriate, group, to, redirect, replies...
Message-ID	<eeFfw.45208$Ox2.3714@fx46.am4> (permalink)
Date	2014-12-03 14:36 +0000

Cross-posted to 2 groups.

Followups directed to: Choose, an, appropriate, group, to, redirect, replies...

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Victor Bazarov wrote:

> On 12/3/2014 8:57 AM, jacob navia wrote:
>> Le 03/12/2014 14:02, James Kuyper a écrit :
>>> On 12/03/2014 05:19 AM, Melzzzzz wrote:
>>> ...
>>>> int testNormal(const vector_t & ghs, const vector_t & lhs) {
>>> ...
>>>> where: typedef vector<int> vector_t;
>>>
>>> Cross-posting to comp.lang.c a question about code that can't even be
>>> compiled as C code is pointless.
>>>
>>
>> He wrote (and you did not quote that)
>>
>>  > (could be also plain array so I post this to clc as well)
>>
>> Read for comprehension next time.
> 
> The code uses references and a member function.  Do those exist in C?

No, but plain arrays do.

> (it's been some time since I touched C)

It's good for you. Stops you getting scurvy or rickets or something like 
that.

> And if vector_t is a "plain
> array", how can it have a member ('size') at all?

In a sense, of course, it can't. Nevertheless, a number of trivial solutions 
to the problem do exist. You can use an extra parameter to allow the size to 
be passed in, or you can make vector_t a structure type which contains not 
only the array but also the size. (If it's dynamic, you keep a count. If 
it's static, you can just sizeof arr / sizeof arr[0], provided it's safely 
tucked up inside the struct.)

-- 
Richard Heathfield
Email: rjh at cpax dot org dot uk
"Usenet is a strange place" - dmr 29 July 1999
Sig line 4 vacant - apply within

Thread

Why compiler is able to vectorize on int but not on unsigned Melzzzzz <mel@zzzzz.com> - 2014-12-03 11:19 +0100
  Re: Why compiler is able to vectorize on int but not on unsigned James Kuyper <jameskuyper@verizon.net> - 2014-12-03 08:02 -0500
    Re: Why compiler is able to vectorize on int but not on unsigned jacob navia <jacob@spamsink.net> - 2014-12-03 14:57 +0100
      Re: Why compiler is able to vectorize on int but not on unsigned Tim Prince <tprince@computer.org> - 2014-12-03 09:23 -0500
        Re: Why compiler is able to vectorize on int but not on unsigned James Kuyper <jameskuyper@verizon.net> - 2014-12-03 10:03 -0500
      Re: Why compiler is able to vectorize on int but not on unsigned Victor Bazarov <v.bazarov@comcast.invalid> - 2014-12-03 09:24 -0500
        Re: Why compiler is able to vectorize on int but not on unsigned Richard Heathfield <invalid@see.sig.invalid> - 2014-12-03 14:36 +0000
    Re: Why compiler is able to vectorize on int but not on unsigned Melzzzzz <mel@zzzzz.com> - 2014-12-03 16:03 +0100
      Re: Why compiler is able to vectorize on int but not on unsigned Victor Bazarov <v.bazarov@comcast.invalid> - 2014-12-03 10:27 -0500
        Re: Why compiler is able to vectorize on int but not on unsigned Melzzzzz <mel@zzzzz.com> - 2014-12-03 16:43 +0100
  Re: Why compiler is able to vectorize on int but not on unsigned red floyd <no.spam@its.invalid> - 2014-12-03 08:59 -0800
  Re: Why compiler is able to vectorize on int but not on unsigned Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2014-12-03 18:53 +0100
    Re: Why compiler is able to vectorize on int but not on unsigned James Kuyper <jameskuyper@verizon.net> - 2014-12-03 13:13 -0500
      Re: Why compiler is able to vectorize on int but not on unsigned Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2014-12-04 22:04 +0100
        Re: Why compiler is able to vectorize on int but not on unsigned Melzzzzz <mel@zzzzz.com> - 2014-12-05 10:07 +0100
          Re: Why compiler is able to vectorize on int but not on unsigned Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2014-12-05 10:42 +0100
            Re: Why compiler is able to vectorize on int but not on unsigned Melzzzzz <mel@zzzzz.com> - 2014-12-05 11:29 +0100

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