Hi Philippe,
> > Do you know of a better solution (than returning to the loop)?
There is a solution. Simple example for int, for others is similar:
root.exe [0] int a[10]
root.exe [1] a[0]=2004
(const int)2004
root.exe [2] memcpy(a+1,a,9*4)
(void*)0x87f9c84
root.exe [3] a[1]
(int)2004
root.exe [4] a[2]
(int)2004
Victor
Victor M. Perevoztchikov perev@bnl.gov
Brookhaven National Laboratory MS 510A PO Box 5000 Upton NY 11973-5000
tel office : 631-344-7894; fax 631-344-4206;
----- Original Message -----
From: "Peter Elmer" <Peter.Elmer@cern.ch>
To: "Philippe Canal" <pcanal@fnal.gov>
Cc: <roottalk@pcroot.cern.ch>
Sent: Friday, April 02, 2004 1:52 PM
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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