Java can be significantly faster than C

Preface

When I wrote this article it was to comment on how writing the same algorithm implement a different way can make a major difference. I now believe this is not the point of the web site perhaps shouldn't be the point of this article either. I have written a follow up article.

The importance of innovation

Overview

Whether you use Java or C is not always as important as the approach you use. By "approach" I mean; algorithms not specified in the requirements or "the how" to do something.

You might not see this as a fair test of Java vs C, but in the real world human factors are matter. There is no point saying C is faster in theory but there isn't anyone available to make it so. Its like getting a very cheap price on an item which is not in stock. ;)

Benchmark Shootout

Java is temporarily the fastest for this particular knucleotide benchmark. It is quite likely that if the algorithm I used is translated to C it would be faster again. But for the moment Java is fastest because it uses a different approach in a number of key places.

Benchmark results at Wed 31st August 2011.

If anyone is interested in translating it to C, I would like to know how much faster it is. ;)

Making it faster again

On my home PC it only takes 0.684 ms, a gain of 2.5x. My PC uses newer hardware (and an over clocked CPU)

The code

Asking multiple AI to optimise the same code

As different AIs are implemented differently, they don't all provide the same answer, nor do they consistently outperform one another. The best approach is to use multiple AI and pick the one you like best. My goal here is not to declare a winner based on one example, but instead to show the variety of answers you can get with different AI. I asked each AI to Suggest how to implement this more optimally private static String formatOffset(int millis) { String sign = millis < 0 ? "-" : "+"; int saveSecs = Math.abs(millis) / 1000; int hours = saveSecs / 3600; int mins = ((saveSecs / 60) % 60); int secs = (saveSecs % 60); if (secs == 0) { if (mins == 0) { return sign + twoDigitString(hours); } return sign + twoDigitString(hours) + twoDigitString(mins); } return sign + twoDigitString(hours) + twoDigitString(mins) + twoDigitString(secs); } private static String twoDigitString(int value) { ...

Demystifying Java Object Sizes: Compact Headers, Compressed Oops, and Beyond

Introduction Measuring an object’s size in Java is not straightforward. The platform encourages you to consider references and abstractions rather than raw memory usage. Still, understanding how objects fit into memory can yield significant benefits, especially for high-performance, low-latency systems. Over time, the JVM has introduced optimisations like Compressed Ordinary Object Pointers (Compressed Oops) and, more recently, Compact Object Headers. Each of these can influence how large or small your objects appear. Understanding these factors helps you reason about memory usage more concretely. Measuring Object Sizes In principle, you can estimate an object’s size by creating instances and observing changes in the JVM’s free memory. However, you must neutralise certain factors to get consistent results. For example, turning off TLAB allocation ( -XX:-UseTLAB ) makes memory usage more directly observable. Repeated measurements and median calculations can reduce the im...

Updated Biography

Peter Lawrey is an Australian/British software engineer and entrepreneur best known for work on ultra-low-latency Java systems and for leading the open-source OpenHFT libraries. He is the founder and chief executive of Chronicle Software, a London-based company whose technology is used in trading and market-infrastructure workloads. Lawrey is also a recognised Java community figure: he was named a Java Champion in 2015, has been described by conference organisers as having provided the most answers for the Java and JVM tags on Stack Overflow, and writes the long-running Vanilla Java blog. ( Chronicle Software , javachampions.org , qconnewyork.com , blog.vanillajava.blog ) Career Lawrey founded and leads Chronicle Software, which builds enabling technology for event-driven trading and market-data platforms. The company states that its software underpins systems at several tier-one banks; a 2024 press announcement similarly described Chronicle as supplying "8 of the t...