Xref: utzoo comp.lang.c:7085 comp.unix.wizards:6424
Path: utzoo!mnetor!uunet!husc6!mit-eddie!uw-beaver!uw-june!pardo
From: pardo@june.cs.washington.edu (David Keppel)
Newsgroups: comp.lang.c,comp.unix.wizards
Subject: Re: Faster C
Message-ID: <4177@june.cs.washington.edu>
Date: 6 Feb 88 02:26:13 GMT
References: <473@aati.UUCP>
Reply-To: pardo@uw-june.UUCP (David Keppel)
Organization: U of Washington, Computer Science, Seattle
Lines: 23
Keywords: 4.1bsd, performance, 11/750

In article <473@aati.UUCP> fish@aati.UUCP (William G. Fish) writes:
->I wish to make the following C code run as fast as possible under 4.1 BSD 
->on a VAX 11/750.  I've seen VAX instructions such as movc3 and cmpc3 make
->code run 10 to 50 times faster.  Are there any CISC instructions that can
->be used in this case?
->
->scan(in, out, c, C, S)
->    register short *in;
->    register float *out;
->    register c;
->    int C, S;
->{
->    register sample;
->    register s;
->
->    for (s = 0; s < S; s++, c += C)
->    {
->	out[s] = sample = in[c];	/* short to float conversion */

If you change the out[s] and in[c] to use a pointer that is incremented
each iteration, you may be able to save yourself an ashl each time.

	;-D on  (*gazing)  Pardo