Xref:	news2.mv.net comp.os.msdos.djgpp:4945
From:	davis AT space DOT mit DOT edu (John E. Davis)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Speed optimization: memcpy() or for loop ??
Date:	13 Jun 1996 18:41:21 GMT
Organization:	Center for Space Research
Lines:	35
Message-ID:	<slrn4s0o6h.71s.davis@aluche.mit.edu>
References:	<4pmlrp$p7u AT crc-news DOT doc DOT ca> <4pmscu$nrt AT rs18 DOT hrz DOT th-darmstadt DOT de> <4pn7dp$2d2 AT crc-news DOT doc DOT ca>
Reply-To:	davis AT space DOT mit DOT edu
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To:	djgpp AT delorie DOT com
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On 12 Jun 1996 19:56:41 GMT, Richard Young <richard DOT young AT crc DOT doc DOT ca>
wrote:
 :  >for(i=n,px=x,py=y; i ; i--) *py++=*px++;
I would write this as:

     pxmax = px + n;
     while (px < pxmax) *py++ = *px++;

or if the address space is flat:

     diff = py - px;
     pxmax = px + n;
     while (px < pxmax) 
       {
         *(px + diff) = *px;
	 px++;
       }

Also, if n is a multiple of 2, one could do:

     diff = py - px;
     pxmax = px + n;
     while (px < pxmax) 
       {
         *(px + diff) = *px;
	 px++;
         *(px + diff) = *px;
	 px++;
       }

-- 
John E. Davis                   Center for Space Research/AXAF Science Center
617-258-8119                    MIT 37-662c, Cambridge, MA 02139
http://space.mit.edu/~davis

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