Java code is running faster than equivalent C++ code

I did not believe it at first, but it seems true: a fuzzy matching algorithm that I wrote is running faster implemented in Java than in C++ (about 5% faster).

A few caveates: the Java code is part of a large very long running server process so Hotspot has had a lot of time to optimize the code. Also, about 90% of the runtime of the entire system is in the small section of code that I reimplemented in C++ - this is about as good a scenario for Hotspot optimization than you could hope for. The particulars:

Java JVM: J2RE 1.4.2 IBM build for PowerPC.
C++: GNU g++ used with -O3

The code uses a packed block of 8 bit byte values that is about 4 megabytes. There is no code in this algorithm that could be optimized away: just some nested loops comparing byte values and performng a few sums.

Java on the server is not slow! This is for a customer project, and to get better performance I was willing to recode the whole thing in C++ if there had been an appreciable performance gain - obviously I won't do that now :-)

Comments

Post a Comment

Popular posts from this blog

My Dad's work with Robert Oppenheimer and Edward Teller

Robert Oppenheimer and Edward Teller facilitated my Dad getting a professorship at UC Berkeley when I was 3 years old. Oppenheimer left Berkeley but Teller was a good friend of my father and I remember him being in our home. Three weeks ago, my wife and I were just leaving to see the new Oppenheimer movie when my Dad called. He mentioned that when I was in grade school he was invited to give a talk at Princeton. After his talk Oppenheimer talked with my Dad and invited him to have dinner at his house. My Dad said Oppenheimer was not well (I think he died of throat cancer soon afterwards) but his wife Kitty carried the conversation. My Dad, Ken Watson, passed away 10 days ago on August 18, 2023.
Read more

Time and Attention Fragmentation in Our Digital Lives

  As humans we have evolved over a few million years to be both attentive and reactive to danger, live in social communities, and spend much of our time being in the present moment gathering and eating food and socializing. The behavior of rapidly changing short attention to content on social media, too many good short form things to watch on streaming video entertainment platforms, are all rewiring our brains in an unnatural and unhealthy way. I fight back, but in really simple ways that entail little ceremony: Almost every morning I spend 30 minutes scanning Hacker News (about 10 minutes), Apple News (about 5 minutes), and the remaining time on Twitter and Mastodon finding interesting new (mostly tech) things. I make notes in a temporary Apple Note: links of things I may want to research, try, or simply read that day. I like to get this all done at once, and then not feel like I need to interrupt my activities during the day to “catch up” on what is happening in the world. In a way,
Read more

Ruby Sinatra web apps with background work threads

In Java-land, I have often used the pattern of writing a servlet with an init() method that starts up one or more background work threads. Then while my web application is handling HTTP requests the background threads can be doing work like fetching RSS feeds for display in the web app, perform periodic maintenance like flushing old data from a database, etc. This is a simple pattern that is robust and easy to implement with a few extra lines of Java code and an extra servlet definition in a web.xml file. In Ruby-land this pattern is even simpler to implement: require 'rubygems' require 'sinatra' $sum = 0 Thread.new do # trivial example work thread while true do sleep 0.12 $sum += 1 end end get '/' do "Testing background work thread: sum is #{$sum}" end While the main thread is waiting for HTTP requests the background thread can do any other work. This works fine with Ruby 1.8.7 or any 1.9.*, but I would run this in JRuby for a lon
Read more