🚀 go-pugleaf

A friend of mine was making some speed comparisions between
a Compaq 386 and a Mac II.  The results seem a little strange,
so I thought I'd see if anyone who knows about the 386 could
shed some light on this.

The benchmarks were written in Fortran.  The MacII version used
Absoft's version 2.3/020 Fortran compiler (with the 020/881
switches on).  I dont know the details of the Compaq, but I was told it
is a 386 with a 387 (running at either 16 or 20 MHz).  Unfortunately
I dont know anything about the Fortran compiler for the Compaq.

Two benchmark programs were run.  They are both very short, so I
included the source below.  The first benchmark solves an ODE, doing
a lot of trig functions.  On the Mac II this takes about 27 seconds to
run.  The Compaq ran about a factor of 3 slower than the Mac II
(I dont have the exact execution time with me).  The second program
basically just does a lot of adds of array elements.  The Mac II version
ran in just over 40 sec.  On the other hand the Compaq ran it about 
5 times faster (about 8 sec)!

Why should there be such a large discrepency (x15) in the execution times
for these two cases?  Has anyone else tried similar comparisons between
the two machines?  If so, I'd appreciate hearing about it.  I guess this
underscores the fact that benchmarks should be taken with a large
grain of salt.

BTW - this is not intended to start an 020/386 war....

Thanks heaps,

Kevin Housen


Benchmark #1:

c....	program solves ode system y'=x*sin(y+z2)-cos(x2+y/(1.+y2))2
c....	z'=-(y2-x2)*e(-(y+z)2)/(1.+C(abs(x+y+z)))
	x=0.
	y=1.
	z=1.
	dx=.001
	do (kk=1,100000)
	  y1=y+dx*(x*sin(y+z*z)-cos(x*x+y/(1.+y*y))**2)
	  z1=z-dx*(y*y-x*x)*exp(-(y+z)**2)/(1.+sqrt(abs(x+y+z)))
	  y=y1
	  z=z1
	  x=x+dx
	repeat
	end

Benchmark #2:
	real*4 a(101,101)
	do (i=1,101)
	  do (j=1,101)
	    a(i,j)=0.
	  repeat
	repeat
	do (i=1,101)
	  a(1,i)=1.
	  a(101,i)=0.
	  a(i,1)=1.
	  a(i,101)=1.
	repeat
	do (kk=1,50)
	  do (i=2,100)
	    do (j=2,100)
	      a(i,j)=0.25*(a(i+1,j)+a(i-1,j)+a(i,j-1)+a(i,j+1))
	    repeat
	  repeat
	repeat
	end