[boost] units: performance testing

From: Lewis Hyatt (lhyatt_at_[hidden])
Date: 2007-03-28 15:54:05

Hello-

I don't think I will have time to write a full review of units (and I 
probably don't know enough to seriously critique it anyway), but FWIW, I 
think it should be accepted, and it looks quite useful and well designed 
to me.

I did try some quick performance tests out of curiosity on a few 
different systems. Here is the output of the unit_example_14 test 
program for:

1) gcc 3.4.4 on WinXP / MinGW (Intel P4 2.8 GHz)
------------------------------------
f(x,y,z) took 6.593 seconds to run 1e+009 iterations with double = 
6.06704e+008 flops
f(x,y,z) took 10.782 seconds to run 1e+009 iterations with 
quantity<double> = 3.70989e+008 flops
g(x,y,z) took 6.625 seconds to run 1e+009 iterations with double = 
6.03774e+008 flops
g(x,y,z) took 9.906 seconds to run 1e+009 iterations with 
quantity<double> = 4.03796e+008 flops

------------------------------------

2) gcc 3.4.4 on WinXP / cygwin (Intel P4 2.8 GHz)
------------------------------------
f(x,y,z) took 6.5 seconds to run 1e+09 iterations with double = 
6.15385e+08 flops
f(x,y,z) took 10.375 seconds to run 1e+09 iterations with 
quantity<double> = 3.85542e+08 flops
g(x,y,z) took 6.719 seconds to run 1e+09 iterations with double = 
5.95327e+08 flops
g(x,y,z) took 10.531 seconds to run 1e+09 iterations with 
quantity<double> = 3.79831e+08 flops
------------------------------------

3) gcc 3.4.6 on Linux (Intel Xeon 3.2 GHz)
------------------------------------
f(x,y,z) took 13.76 seconds to run 1e+09 iterations with double = 
2.90698e+08 flops
f(x,y,z) took 17.34 seconds to run 1e+09 iterations with 
quantity<double> = 2.30681e+08 flops
g(x,y,z) took 13.82 seconds to run 1e+09 iterations with double = 
2.89436e+08 flops
g(x,y,z) took 14.76 seconds to run 1e+09 iterations with 
quantity<double> = 2.71003e+08 flops
------------------------------------

4) gcc 3.4.6 on Linux (AMD Athlon 1.6GHz)
------------------------------------
f(x,y,z) took 27.83 seconds to run 1e+09 iterations with double = 
1.4373e+08 flops
f(x,y,z) took 33.22 seconds to run 1e+09 iterations with 
quantity<double> = 1.20409e+08 flops
g(x,y,z) took 27.54 seconds to run 1e+09 iterations with double = 
1.45243e+08 flops
g(x,y,z) took 30.68 seconds to run 1e+09 iterations with 
quantity<double> = 1.30378e+08 flops
------------------------------------

So gcc, at least, seems to be able to tell the difference when the units 
are being used, at the level of a few tens of percent. This was compiled 
with

        g++ -s -O3 -DNDEBUG

I also tried compiling with gcc 3.3.3 but got a large number of 
errors... I attached the gzipped output in case that is interesting, but 
maybe this compiler is not supposed to be supported anyway?

-Lewis