Coding Horror

programming and human factors

For Best Results, Don't Initialize Variables

I noticed on a few projects I'm currently working on that the developers are maniacal about initializing variables. That is, either they initialize them when they're declared:

  
private string s = null;  
private int n = 0;  
private DataSet ds = null;  

Or they initialize them in the constructor:

  
class MyClass  
{
private string s;  
private int n;  
private DataSet ds;  
public MyClass()  
{
s = null;  
n = 0;  
ds = null;  
}
}

Well, this all struck me as unnecessary work in the .NET world. Sure, maybe that's the convention in the wild and wooly world of buffer overrunsC++, but this is managed code. Do we really want to play the I'm smarter than the runtime game again?

Ok, so maybe you're a masochist and you like extra typing. What about the performance argument? According to this well-researched CodeProject article, initializing variables actually hurts performance. The author provides some benchmark test code along with his results:

Creating an object and initializing on definition11% slower
Creating an object and initializing in the constructor16% slower
Calling a method and initializing variables25% slower

That's on the author's Pentium-M 1.6ghz. I tested the same code (optimizations enabled, release mode) on my Athlon 64 2.1ghz and a Prescott P4 2.8ghz:

Athlon 64P4
Creating an object and initializing on definition30% slower35% slower
Creating an object and initializing in the constructor30% slower36% slower
Calling a method and initializing variables14% slower8% slower

I recompiled under VS.NET 2005 beta 2 using the Athlon 64 to see how .NET 2.0 handles this:

Creating an object and initializing on definition0% slower
Creating an object and initializing in the constructor20 % slower
Calling a method and initializing variables20% slower

Clearly there's a substantial performance penalty for initializing variables in both .NET 1.1 and even .NET 2.0 (although the newer compiler appears to optimize away initialization on definition). I recommend avoiding initialization as a general rule, unless you have a compelling reason to do so. If you're only initializing variables to avoid the uninitialized variable compiler warning, check out the new #pragma warning feature to programmatically disable specific warnings in .NET 2.0.

Written by Jeff Atwood

Indoor enthusiast. Co-founder of Stack Exchange and Discourse. Disclaimer: I have no idea what I'm talking about. Find me here: http://twitter.com/codinghorror