Is Scala functional programming slower than traditional coding?

In one of my first attempts to create functional code, I ran into a performance issue.

I started with a common task - multiply the elements of two arrays and sum up the results:

var first:Array[Float] ...
var second:Array[Float] ...    
var sum=0f; 
for (ix<-0 until first.length) 
    sum += first(ix) * second(ix);

Here is how I reformed the work:

sum = first.zip(second).map{ case (a,b) => a*b }.reduceLeft(_+_)

When I benchmarked the two approaches, the second method takes 40 times as long to complete!

Why does the second method take so much longer? How can I reform the work to be both speed efficient and use functional programming style?

performance scala functional-programming

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To answer the question in the title: Simple functional constructs may be slower than imperative on the JVM.

But, if we consider only simple constructs, then we might as well throw out all modern languages and stick with C or assembler. If you look a the programming language shootout, C always wins.

So why choose a modern language? Because it lets you express a cleaner design. Cleaner design leads to performance gains in the overall operation of the application. Even if some low-level methods can be slower. One of my favorite examples is the performance of BuildR vs. Maven. BuildR is written in Ruby, an interpreted, slow, language. Maven is written in Java. A build in BuildR is twice as fast as Maven. This is due mostly to the design of BuildR which is lightweight compared with that of Maven.

answered 2010-05-09T07:28:13.280

Is Scala functional programming slower than traditional coding?

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