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Faster Java on Raspberry Pi
With the official announcement of Oracle Java on Raspberry Pi, Java just got usable on the Raspberry Pi. It’s still not super-fast, but I’m seeing ~10× speedup over OpenJDK.
To install it (on Raspbian):
sudo apt-get update && sudo apt-get install oracle-java7-jdk sudo update-java-alternatives -s jdk-7-oracle-armhf
By way of a baseline, here are SciMark 2.0 results on OpenJDK:
$ java -classpath ./scimark2lib.jar jnt.scimark2.commandline -large SciMark 2.0a Composite Score: 2.4987047508570632 FFT (1048576): 1.5550941987343943 SOR (1000x1000):Â Â 5.32030759023185 Monte Carlo : 0.6005590152716936 Sparse matmult (N=100000, nz=1000000): 2.3584905938878946 LU (1000x1000): 2.6590723561594847 java.vendor: Sun Microsystems Inc. java.version: 1.6.0_27 os.arch: arm os.name: Linux os.version: 3.6.11+
Here’s what the Oracle JDK cranks out (bigger numbers → better):
$ java -classpath ./scimark2lib.jar jnt.scimark2.commandline -large SciMark 2.0a Composite Score: 14.94896390647437 FFT (1048576): 6.953238474333376 SOR (1000x1000):Â Â 33.91437255527547 Monte Carlo : 8.869794361002157 Sparse matmult (N=100000, nz=1000000): 9.81896340073432 LU (1000x1000): 15.188450741026523 java.vendor: Oracle Corporation java.version: 1.7.0_40 os.arch: arm os.name: Linux os.version: 3.6.11+
That’s a tidy increase, and might make Processing and Arduino much easier to work with.
(It’s still not tremendously fast, though. My i7 quad-core has a composite score of nearly 1450 …)
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BeagleBone Black: slow as a dog
All benchmarks are artificial, but this one had me scratching my head. One hears that the BeagleBone Black is screamingly fast compared to the Raspberry Pi; faster, newer processor, blahdeblah, mcbtyc, etc. I found the opposite is true.
So I buy one at the exceptionally soggy Toronto Mini Maker Faire. Props to the CircuitCo folks, they are easy to set up: just a mini-USB cable provides power and virtual network shell. And BoneScript — an Arduino-like JavaScript library — is very clever indeed. But I need to see if this thing has any grunt, and so I need a benchmark.
After hearing about the business-card raytracer, I thought it would be perfect. I compiled it on both machines with:
g++ -Ofast  card.cpp  -o card
and then ran it with:
time ./card > /dev/null
The results are … surprising:
- Raspberry Pi: 4′ 15″
- BeagleBone Black: 12′ 39″ → 3× slower
(In comparison, my i7 quad-core laptop runs it in 8½ seconds.)
I don’t have any explanation why the BBB is so much slower. It’s almost as if the compiler isn’t fully optimizing under Ã…ngström Linux.
Raspberry Pi: system info
$ uname -a Linux rpi 3.6.11+ #538 PREEMPT Fri Aug 30 20:42:08 BST 2013 armv6l GNU/Linux $ cat /proc/cpuinfo Processor   : ARMv6-compatible processor rev 7 (v6l) BogoMIPS   : 697.95 Features   : swp half thumb fastmult vfp edsp java tls CPU implementer   : 0x41 CPU architecture: 7 CPU variant   : 0x0 CPU part   : 0xb76 CPU revision   : 7 Hardware   : BCM2708 Revision   : 000f
BeagleBone Black: system info
# uname -a Linux beaglebone 3.8.13 #1 SMP Tue Jun 18 02:11:09 EDT 2013 armv7l GNU/Linux # cat /proc/cpuinfo processor   : 0 model name   : ARMv7 Processor rev 2 (v7l) BogoMIPS   : 297.40 Features   : swp half thumb fastmult vfp edsp thumbee neon vfpv3 tls CPU implementer   : 0x41 CPU architecture: 7 CPU variant   : 0x3 CPU part   : 0xc08 CPU revision   : 2 Hardware   : Generic AM33XX (Flattened Device Tree) Revision   : 0000
Both boards are running at stock speed.
Update: I’ve tried with an external power supply, and checked that the processor was running at full speed. It made no difference. I suspect that Raspbian enables armhf floating point by default, while Ã…ngström needs to be told to use it.
