Thanks for this great explanation Henrik. Nevertheless, my question is still valid. Why Set new will give me an internal array of 5 elements while Set new: 1 will give me an internal array of 7 elements? Shouldn’t Set new give an internal of 7 elements as it looks like the minimal array size for a set? Also I would expect Set new: 0 to give me an empty internal array. It explicitly ask an empty Set. A further call to #add: will increase its size as expected.
> Le 1 déc. 2016 à 13:25, Henrik Nergaard <henrik.nerga...@uia.no> a écrit : > > Hashed collections keep a portion of the available memory empty (usually 25%) > as a partition mechanism to increase lookup speed. > > “Normal array” > | col | > > col := Smalltalk allClassesAndTraits asArray. > > [ col includes: 8; includes: Morph ] bench. "'366.853 per second'" > > “Normal set ~75% load” > | set | > > set := Smalltalk allClassesAndTraits asSet. > > [ set includes: 8; includes: Morph ] bench. "'4,700,967 per second'" > > > “Set forced to have ~100% load” > | array fullLoadSet | > > array := Smalltalk allClassesAndTraits asSet asArray , #(nil). > fullLoadSet:= Set basicNew. > fullLoadSet > instVarNamed: #array put: array; > instVarNamed: #tally put: array size. > > [ fullLoadSet includes: 8; includes: Morph ] bench. "'215.157 per second'" > > > Best regards, > Henrik > > > From: Pharo-dev [mailto:pharo-dev-boun...@lists.pharo.org] On Behalf Of > Christophe Demarey > Sent: Thursday, December 1, 2016 11:49 AM > To: Pharo Development List <pharo-dev@lists.pharo.org> > Subject: [Pharo-dev] Set internal array size > > Hi, > > I just discovered a funny thing. > If you create a Set with Set new, you will get a Set with an internal array > of 5 elements (hardcoded in Set class>>#new). > If you ask explicitly a Set for one or no element: Set new: 0 (or a number > between 0 and 5), you will get an internal array of 7 elements. > This behavior is a bit strange. Either we always need at least 7 elements and > we need to update Set class>>#new, either the method Set class>>#sizeFor: > should be updated. > > WDYT? > > Christophe
