performance - Conversion between different implementations of Seq in Scala -

from have read, 1 should prefer use generic seq when defining sequences instead of specific implementations such list or vector.

though have parts of code when sequence used full traversal (mapping, filtering, etc) , parts of code same sequence used indexing operations (indexof, lastindexwhere).

in first case, think better use linearseq (implem list) whereas in second case better use indexedseq (implem vector).

my question is: need explicitly call conversion method tolist , toindexedseqin code or conversion done under hood in intelligent manner ? if use these conversions, penalty performance when going , forth between indexedseq , linearseq ?

thanks in advance

vector out-perform list. unless algorithm uses ::, head , tail, vector faster list. using list more of conceptual question on algorithm (data stack-structured, accessing head/tail, adding elements prepending, use of pattern matching (which can used vector, feels more natural me use list)).

you might want @ why should use vector in scala

now nice number compare (obviously not 'real' benchmark, eh) :

val l = list.range(1,1000000) val = vector.range(1,1000000)  import system.{currenttimemillis=> milli}  val startlist = milli l.map(_*2).map(_+2).filter(_%2 == 0) println(s"time list map/filter operations : ${milli - startlist}")  val startvector = milli a.map(_*2).map(_+2).filter(_%2 == 0) println(s"time vector map/filter operations : ${milli - startvector}") 

output :

time list map/filter operations : 1214   time vector map/filter operations : 364 

edit : realized doesn't answer question. far know, have call tolist/tovector yourself. performances, depends on sequence, unless you're going , forth time, shouldn't problem.

once again, not serious benchmark, :

val startconvtolist = milli a.tolist println(s"time conversion list: ${milli - startconvtolist}")  val startconvtovector = milli l.tovector println(s"time conversion vector: ${milli - startconvtovector}") 

output :

time conversion list: 48 time conversion vector: 18