Hi Peter,
The problem will be correct in the CVS repository as soon as Fons
comes back (next week).
Cheers,
Philippe
-----Original Message-----
From: Peter Elmer [mailto:Peter.Elmer@cern.ch]
Sent: Friday, April 02, 2004 12:53 PM
To: Philippe Canal
Cc: roottalk@pcroot.cern.ch
Subject: Re: [ROOT] TArrayI::Reset() implementation change
Hi Philippe,
On Fri, Apr 02, 2004 at 12:30:38PM -0600, Philippe Canal wrote:
> I don't think that this is intentional.
> The change was made (incorrectly!) to improve speed without changing
> behavior.
>
> Do you know of a better solution (than returning to the loop)?
Sorry, unfortunately no. (In fact it was even pointed out to me by
someone in BaBar that "memset isn't even consistently faster than a simple
loop", at least according to some tests done a few years ago. I've not
verified that myself.)
Pete
> -----Original Message-----
> From: owner-roottalk@pcroot.cern.ch
> [mailto:owner-roottalk@pcroot.cern.ch]On Behalf Of Peter Elmer
> Sent: Friday, April 02, 2004 6:07 AM
> To: roottalk@pcroot.cern.ch
> Subject: [ROOT] TArrayI::Reset() implementation change
>
>
> Hi Rene,
>
> I see that between ROOT 3.10-01 and 3.10-02, the following change was
made
> to TArrayI::Reset(...):
>
> < // @(#)root/cont:$Name: $:$Id: TArrayI.h,v 1.14 2002/10/30 20:39:50
brun
> Exp $
> ---
> > // @(#)root/cont:$Name: $:$Id: TArrayI.h,v 1.16 2003/11/14 11:17:13
brun
> Exp $
> 44c44
> < void Copy(TArrayI &array) const {array.Set(fN); for (Int_t
> i=0;i<fN;i++) array.fArray[i] = fArray[i];}
> ---
> > void Copy(TArrayI &array) const {array.Set(fN,fArray);}
> 48,49c48
> < void Reset() {memset(fArray, 0, fN*sizeof(Int_t));}
> < void Reset(Int_t val) {for (Int_t i=0;i<fN;i++) fArray[i] =
> val;}
> ---
> > void Reset(Int_t val=0) {memset(fArray,val,
> fN*sizeof(Int_t));}
>
> For values of val other than 0, I think this actually changes the
> implementation since memset (IIRC) fills the array >byte-by-byte< with
> the value "val" (and not array-index by array-index). Was that change
> intentional? (We were relying on the original implementation in some of
our
> code.)
>
> thanks,
> Pete
>
-------------------------------------------------------------------------
Peter Elmer E-mail: Peter.Elmer@cern.ch Phone: +41 (22) 767-4644
Address: CERN Division PPE, Bat. 32 2C-14, CH-1211 Geneva 23, Switzerland
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