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

From Tim Prince <tprince@computer.org>
Newsgroups comp.lang.c++, comp.lang.c
Subject Re: Why compiler is able to vectorize on int but not on unsigned
Date 2014-12-03 09:23 -0500
Message-ID <ce8kmcFo0j3U1@mid.individual.net> (permalink)
References <20141203111909.5ec8c7fc@maxa-pc> <m5n1l8$m45$1@dont-email.me> <m5n4rq$k42$1@speranza.aioe.org>

Cross-posted to 2 groups.

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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.
but OP leaves it open to guesswork on what extent he simplifies the
problem for C.
OP also leaves his choice of compiler and target open for guesswork.
However, unsigned indexing is notoriously (perhaps even surprisingly)
difficult to deal with in vectorization, particularly on ia32 target.

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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
  Why compiler is able to vectorize on int but not on unsigned "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2014-12-03 06:35 -0800
    Re: Why compiler is able to vectorize on int but not on unsigned Melzzzzz <mel@zzzzz.com> - 2014-12-03 16:09 +0100
  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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