Content deleted Content added
m Signing comment by 188.126.207.212 - "→C & C++ have Dimension = 1?: " |
Add discussion on iliffe vector implementation |
||
Line 277:
* <p>It looks like the definition of Array Data Structure cites Dictionary of Algorithms and Data Structures definition of array, which says, "Array (data structure) An assemblage of items that are randomly accessible by integers, the index." This matches the WP definition of "Array Data Type", and not so much the WP "Array Data Structure" definition, and says nothing about indexing by physical address (itself a questionable link in this day of virtual memory) by formula. Additionally the ADT information from the DADS entry appears on the Array Data Type page, not here, but is cited here, not there.</p><p>AOCP1 is also cited, and Knuth does have a simple formula on p 244 where he talks about: Linear Lists (which are 1D arrays per p 4 & 629) with Sequential Allocation. A similar formula appears for multidimensional arrays on p 299 with Sequential Allocation, where Sequential Allocation is just a straight-up allocation of a block of words (i.e. a normal array data structure). However, Knuth goes on to then discuss "arrays" with Linked Allocation (i.e. a linked list) on pages 254 and 301. That is to say, he is speaking of arrays in the WP "Array Data Structure" sense when he is talking about Sequential Allocation, but in the WP "Array Data Type" sense when he is talking about Linked Allocation. But since they're all "arrays" to him, WP is making a terminology distinction that Knuth does not seem to be making in the same way.</p><p>So I'm not sure the definitions we're using here are well-backed by their citations.</p><p>Plus, the two pages are very confusing for reasons I don't quite understand (and I'm a pretty experienced computer guy). Arrays as an ADT and as an implementation whether by "sequential allocation", "linked allocation", or otherwise, are a very simple concept to present, so there is no reason why the articles should be anything other than crystal clear. I'm willing to take a stab at it, but there's obviously a lot of history here and I'm reluctant to get involved. So just put this down as a vote for "needs work". [[User:Beej71|Beej71]] ([[User talk:Beej71|talk]]) 12:29, 7 January 2010 (UTC)</p>
==iliffe array==
The implementation of the iliffe array presented here makes the assumption that each row is allocated separately. However, Numerical Recipes in C provide a version of such vector with better locality by allocating the data as a contiguous memory block and have the indexing array points to beginning of rows in this block. Tests show few to no overhead between this and a traditional Dope vector. Would it be worthwhile to speak of this distinction ?
[[User:Joel falcou|Joel falcou]] ([[User talk:Joel falcou|talk]]) 18:27, 4 January 2012 (UTC)
| |||