2015-01-16 16:55 GMT+01:00 Eliot Miranda <eliot.mira...@gmail.com>: > Hi All, > > On Jan 16, 2015, at 7:36 AM, Eliot Miranda <eliot.mira...@gmail.com> > wrote: > > > Hi Marcel, > > > > On Jan 16, 2015, at 5:54 AM, Marcel Taeumel < > marcel.taeu...@student.hpi.uni-potsdam.de> wrote: > > > >> Ah, okay. I was curious about the performance of iterating over an > array vs. > >> the linked list: > >> > >> a := Array new: 1000. > >> l := LinkedList new. > >> > >> 1000 timesRepeat: [l add: (StackLink with: nil)]. > >> > >> [a do: [:ea | 1 + 2]] bench. "'94,600 per second.'" > >> > >> [l do: [:ea | 1 + 2]] bench. "'159,000 per second.'" > >> > >> I expected the opposite! :-O Why is that so? > > > > Look at the implementations of do:. > > > > In the Array case we iterate over the indices using SmallIntegers (fast > arithmetic with no allocation) and dereference each element using the > Object>>at: primitive, which (apart from type and bounds checking) is > simple indexed memory access. So one read per element. > > > > In the LinkedList case each list element is fetched from the previous > element and each value fetched from the element, so two reads per element. > > This is interesting. (Marcel, Chris, forgive me; I'm presuming; please > don't take this personally). Marcel above appears to lack an intuition > about the structure of Array vs LinkedList. And in developing a hash > algorithm for a 32-bit subset of Floats a few weeks ago Chris appeared to > lack an I tuition about Floats being boxed, assuming they were value types, > not containers. > > As a VM implementer I carry around a clear picture (literally, I am a > visual thinker) of objects in my head. Those pictures are key to my > approach to design and optimization. > > I presume that for someone approaching the system given only a textual > description of object structures, through class comments and method source > it is difficult to develop a good picture or mental model. For me, I read > the blue book first, which is replete with pictures. > > I know that historically visual inspector frameworks such as Jun have been > able to auto-generate pictorial representations of specific object graphs. > I wonder how useful it would be to provide support for designers to include > pictorial representations in class comments. > > Again I presume that the text model would have to support inclusion of > simple bitmaps (to avoid having to include a full drawing framework in the > system) and that the designer would construct a sample graph, generate a > diagram using a visual inspector framework using eg Jun, render it to a > bitmap and include it in the class comment. >
> > A more elaborate system could of course include the sample graph and > render it dynamically, that would allow exploration. > > Either approach would make an interesting project, yes? > I would prefer something conceptually simpler and worthwhile: the ability to embed a morph as a character in the text (would do the two approaches easily). And a bit of marshalling/text representation to make a completely textual representation possible. I used to have that for hypermedia (i.e. a drawing editor with text frame objects, and text frames able to display GUI components... in ParcPlace Smalltalk) Now I dream a bit of having something like TiddlyWiki in Pharo ;) Thierry
