From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=0.2 required=5.0 tests=BAYES_00,INVALID_MSGID, REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,325a055bed62c230 X-Google-Attributes: gid103376,public From: kilgallen@eisner.decus.org (Larry Kilgallen) Subject: Re: Apex vs GNAT on solaris Date: 1999/12/07 Message-ID: <1999Dec7.084947.1@eisner>#1/1 X-Deja-AN: 557700080 References: <82hiuj$74o$1@nnrp1.deja.com> <82hnll$ahu$1@nnrp1.deja.com> <384cfdb3.691883075@newsnew.draper.com> X-Trace: news.decus.org 944574591 17983 KILGALLEN [216.44.122.34] Organization: LJK Software Reply-To: Kilgallen@eisner.decus.org.nospam Newsgroups: comp.lang.ada Date: 1999-12-07T00:00:00+00:00 List-Id: In article <384cfdb3.691883075@newsnew.draper.com>, rracine@myremarq.com (Roger Racine) writes: > On Tue, 07 Dec 1999 01:25:13 GMT, Robert Dewar wrote: > >>In article <82hiuj$74o$1@nnrp1.deja.com>, >> reason67@my-deja.com wrote: >> >> >>You need to say what options you are using for both compilers. >>We have sometimes found people making the *amazing* mistake >>of compiling GNAT with -O0. Generally the appropriate options >>for benchmarking are -O2 -gnatn. >> >>The options are critical, because otherwise you may simply >>be measuring differences in choices of default options. For >>example if one compiler inlines by default, the other one >>does not, then the comparison may be meaningless. > I have been hit many times by optimizer bugs, and generally assume > that the compiler vendors knows what they are doing when the defaults > are created. They are giving what they think should be the most > common values for the options. For you to say the vendor's default is always your favorite is certainly within your power. But then to say that your favorite settings for compiler #1 produce a faster (or smaller, or smoother, or more gender- neutral) executable than your favorite settings for compiler #2 is quite meaningless if your basis for choosing favorite settings is unrelated to the comparison metric. A compiler vendor may choose their defaults as being "best for those who don't care about settings", which to me pretty much translates into those for whom performance is not a big deal. Larry Kilgallen