Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!leah!rpi!crdgw1!ge-dab!peora!petsd!joe
From: joe@petsd.UUCP (Joe Orost)
Newsgroups: comp.arch
Subject: Re: Understanding variations in Dhrystone performance
Message-ID: <1591@petsd.UUCP>
Date: 18 May 89 16:15:56 GMT
References: <474@estevax.UUCP>
Reply-To: joe@petsd.UUCP (Joseph M. Orost)
Organization: Concurrent Computer Corporation, Tinton Falls, NJ
Lines: 31

<>
Another factor in the Ada performance is whether or not the Ada compiler
supports the pragma PACK, and to what degree.

Compilers that ignore the pragma, along with those that only pack to the
nearest byte or power-of-2 will do better in dhrystone than those that pack
minimally, because the 30-byte strings become 30 7-bit strings.

These bit-packed strings are harder to move and harder to compare, causing
the the dhrystone rating to drop.

This is not fair to implementers that try to provide better support for the
language by supplying minimal bit-packing.

Moving and comparing 7-bit character strings is not something that most users
will do, yet that is what determines the dhrystone number.

My recommendation: throw out the "pragma PACK" on the 30-character
strings.

				regards,
				joe

--

 Full-Name:  Joseph M. Orost
 UUCP:       rutgers!petsd!joe
 ARPA:	     petsd!joe@RUTGERS.EDU, joe@petsd.ccur.com
 Phone:      (201) 758-7284
 US Mail:    MS 313; Concurrent Computer Corporation; 106 Apple St
             Tinton Falls, NJ 07724