Hi All,

On Jan 16, 2015, at 7:36 AM, Eliot Miranda <eliot.miranda@gmail.com> wrote:

> Hi Marcel,
>
> On Jan 16, 2015, at 5:54 AM, Marcel Taeumel <marcel.taeumel@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?