[Reduce-algebra-developers] Reduce on ARM

[Arthur N. <ac...@ca...>]

In March 2016 I reported timings that I observed on various models of 
Raspberry Pi. I now add to that a line that is for an nVidia Jetson TX2, 
which has a multi-core 64-bit ARM clocked at 2GHz, 8GB of main memory and 
32GB of flash memory for its system disk. The development kit comes with a 
SATA connector, so I used a 256GB SSD as my disc drive. This kit is 
distinctly more expensive than the Raspberry Pi, but with educational 
discount is perhaps interesting. Some people would be interested in the 
power of its graphics sub-system and use of that via CUDA. It runs Ubuntu 
16.04 and a key part of its spec is that it should only use 7.5 Watts of 
power (plus whatever the SSD uses, which is also not exactly a lot). I 
think all that makes it a decent choice for a system to be left running 
24x7.

As expected - or at least hoped for - the CSL version of Reduce "just 
built" on it without fuss, and the regression tests deliver results that 
match other platforms.

Here (again) are the numbers from a year ago. Note that the RPI results 
are for 32-bit Linux.

RPI 2   1585.46 seconds   (50:15 mins elapsed time)
RPI 3    752.57 seconds   (21:21 mins elapsed time)
RPI 3    651.20 seconds   (16:22 mins elapsed time, faster micro SD card)
Intel     61.78 seconds   (8:15 mins elapsed time, running on Windows 10)

When I first tried the Jetson the times were unexpectedly close to those 
of the Raspberry Pi 3. After some thought I realised that Reduce has 
changed over that time, and while it should not have slowed down it has 
some new test files that contribute to the total time recorded this way. 
And in particular the sstools takes a lot of time.  So I repeated some 
tests, and today I get the following from "time scripts/testall.sh --csl"

RPI 3, Raspbian 32-bit        913.22 seconds   (25:49 mins elapsed)
Jetson TX2, Ubuntu 16.04      438.83 seconds   (11:25 mins elapsed)
Intel, 64-bit Windows 10,      92.58 seconds   (7:12 mins elapsed)
     i7-4790K, 32GB, 4GHz

So in a year the extra test files for Reduce have added around 40% to the 
total CPU time involved in running the test suite. And the Jetson TX2
in 64-bit mode is beating the Raspberry Pi 3 in 32-bit mode by a factor a 
little over 2 (while the fast PC is still 4.7 times faster yet, but uses 
over 10 times as much electricity at a nominal 88 watts as against a 
nominal 7.5).

[Doing these tests caused me to check Reduce on a 32-bit platform, and you 
will see that that flushed out a couple of bugs in CSL that I needed to 
fix along the way!]