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There is a handy page about performance characteristics of the Scala collection classes. Is there similar data on memory footprint?

I have a situation where I'm concerned about memory use and would like to factor this in my choice of collection to use. For instance, between Array[Array[T]] and Vector[Vector[T]].

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  • Don't you know how to initialize a big Array of Arrays or Vector of Vector? Or don't you know how to measure the memory footprint? I would expect a linear relationship, and try to disprove or prove this idea for some forms of collection. Then measure for some sample sizes up to the limit of my machine. Commented Jun 8, 2011 at 2:49
  • It's more that I haven't performed those measurements and was wondering if anybody knew... Commented Jun 12, 2011 at 4:07

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Here is what I've found out by filling up those respective immutable sequences with 1,000,000 objects on 2.9.0. I had them all point to the same object to factor out the size of the content.

  • Array: 1x (baseline 4,000,016 bytes on 32 bits; 8,000,024 on 64 bits)
  • Vector: 1.17x
  • List, Queue, Stack: 4x
  • evaluated Stream: 10x

System.gc was called then triggered heap dump then opened in Eclipse MAT.

Based on that Array and Vector are pretty closed.

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Vectors can't hold primitives (because they are not specialized (yet?)) but Arrays can. So an Array[Int] would take much less memory than Vector[Int].
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You could start with a simple generation of multiple, multidimensional Vectors and Arrays of different size:

val vMin = Vector.fill (10 , 10)(9) val vMed = Vector.fill (1000, 10)(9) val aMed = Array.fill (1000, 10)(9)

10 Arrays of 10 Arrays of Ints with Value 9, 1000 such Arrays, 1000 such Vectors ...

To measure the size, you could use

$JAVA_HOME/bin/jvisualvm
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