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From: jdb@mordor.UUCP (John Bruner)
Newsgroups: net.works
Subject: Re: assembly vs. HOL
Message-ID: <1563@mordor.UUCP>
Date: Thu, 25-Apr-85 19:09:50 EST
Article-I.D.: mordor.1563
Posted: Thu Apr 25 19:09:50 1985
Date-Received: Sat, 27-Apr-85 03:12:38 EST
References: <1220@topaz.ARPA> <511@terak.UUCP> <1440@amdahl.UUCP>
Organization: S-1 Project, LLNL
Lines: 19

Ackermann's function is very recursive, and the VAX calling sequence
is VERY slow.  The execution time is dominated by the time it takes
to call the recursive function.  Thus, this 750/Z80 comparison is
really comparing one aspect of the architectures of the two machines,
not the difference between assembly and C.  (Does someone want to
volunteer to rewrite Ackermann in MACRO-32?)

By recoding Ackermann as a non-recursive function (in C), I was able
to make my 11/750 run faster than a 4MHz Z80 :-).  My non-recursive
version computes ack(3,6) ten times in 15.4 seconds (user time). 

I am wary of using one program as a benchmark.  For instance, the
VAX-11/780 is faster (overall) than the PDP-11/70; however, my
non-recursive Ackermann takes 7.1 seconds (user) on an 11/780 but
only 6.5 seconds on an 11/70.
-- 
  John Bruner (S-1 Project, Lawrence Livermore National Laboratory)
  MILNET: jdb@mordor.ARPA [jdb@s1-c]	(415) 422-0758
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