MaplePrimes - comments on Post, ListBuffer, a procedure for efficiently building arbitrarily sized lists

MaplePrimes - comments on Post, ListBuffer, a procedure for efficiently building arbitrarily sized lists http://www.mapleprimes.com/posts/43257-ListBuffer-A-Procedure-For-Efficiently en-us 2026 Maplesoft, A Division of Waterloo Maple Inc. Maplesoft Document System Tue, 09 Jun 2026 06:51:09 GMT Tue, 09 Jun 2026 06:51:09 GMT The latest comments added to the Post, ListBuffer, a procedure for efficiently building arbitrarily sized lists http://www.mapleprimes.com/images/mapleprimeswhite.jpg MaplePrimes - comments on Post, ListBuffer, a procedure for efficiently building arbitrarily sized lists http://www.mapleprimes.com/posts/43257-ListBuffer-A-Procedure-For-Efficiently Quite nice http://www.mapleprimes.com/posts/43257-ListBuffer-A-Procedure-For-Efficiently?ref=Feed:MaplePrimes:ListBuffer, a procedure for efficiently building arbitrarily sized lists:Comments#comment80245 This particular trick — dynamically building a table then converting to a list at the end — is something I've used before in a number of places: it's really all you can do when you have to return a list of possibly arbitrary size. However, this particular formalization is particularly nice. I was curious to see how it scaled: since there is a bit of overhead to tables, would adding an element actually be linear with a very small coefficient? It seems not, or at least this coefficient is very small indeed. <pre> N := 100000: A := Array(1..N): lb := ListBuffer(): for i from 1 to N do A[i] := time(lb:-append(i)): end do: plots[pointplot]( [seq([j,A[j]], j=1..N]) ); </pre> The outliers in the plot are probably gc-related. The latest comments added to the Post, ListBuffer, a procedure for efficiently building arbitrarily sized lists 80245 Thu, 19 Jan 2006 20:24:18 Z Stephen Forrest Stephen Forrest Link in post is dead http://www.mapleprimes.com/posts/43257-ListBuffer-A-Procedure-For-Efficiently?ref=Feed:MaplePrimes:ListBuffer, a procedure for efficiently building arbitrarily sized lists:Comments#comment144180 I was looking for Joe's ListBuffer code, but the (seven-year-old) link in the original post is dead. The latest comments added to the Post, ListBuffer, a procedure for efficiently building arbitrarily sized lists 144180 Tue, 05 Mar 2013 03:54:11 Z Carl Love Carl Love Found http://www.mapleprimes.com/posts/43257-ListBuffer-A-Procedure-For-Efficiently?ref=Feed:MaplePrimes:ListBuffer, a procedure for efficiently building arbitrarily sized lists:Comments#comment144183 I found it on the waybackmachine.  Here it is. <a href="/view.aspx?sf=144183/455264/1_ListBuffer.mpl">1_ListBuffer.mpl</a> The latest comments added to the Post, ListBuffer, a procedure for efficiently building arbitrarily sized lists 144183 Tue, 05 Mar 2013 07:25:14 Z Christopher2222 Christopher2222 Page Not Found http://www.mapleprimes.com/posts/43257-ListBuffer-A-Procedure-For-Efficiently?ref=Feed:MaplePrimes:ListBuffer, a procedure for efficiently building arbitrarily sized lists:Comments#comment205496 <a href="/posts/43257-ListBuffer-A-Procedure-For-Efficiently#comment144183">@Christopher2222</a> Unfortunately, the link is dead again, but as I see it, wasn't a (table-based array)-based vector or a one-dimensional Array enough at that time? (And was the use of a <a href="https://www.maplesoft.com/support/help/Maple/view.aspx?path=examples%2FLinkedListPackage">linked list</a> recommended in this situation?) If I have understood correctly, nowadays a better choice should be the newer <a href="https://www.maplesoft.com/support/help/Maple/view.aspx?path=DEQueue">DEQueue</a> object. By the way, is there a similar <a href="https://docs.scala-lang.org/overviews/collections-2.13/performance-characteristics.html">performance characteristic</a> of the built-in <code>StringTools:-StringBuffer</code>? The latest comments added to the Post, ListBuffer, a procedure for efficiently building arbitrarily sized lists 205496 Fri, 22 Sep 2023 03:36:53 Z sursumCorda sursumCorda Four efficient list-building methods http://www.mapleprimes.com/posts/43257-ListBuffer-A-Procedure-For-Efficiently?ref=Feed:MaplePrimes:ListBuffer, a procedure for efficiently building arbitrarily sized lists:Comments#comment205497 <a href="/posts/43257-ListBuffer-A-Procedure-For-Efficiently#comment205496">@sursumCorda</a>  Linked-lists or queues are quite unnecessarily elaborate for this purpose. So-called "flat" and semantics-free containers (rtables, tables) are enough. Here are four efficient methods to build a Maple list: <pre class="prettyprint"> #Note the use of [ ] in this procedure: Nprimes_do:= (n::posint)-> local p, i:= 0; [for p do if gmp_isprime(p) then i++; p fi until i=n] : #Note the use of ,= in this procedure: Nprimes_Array:= proc(n::posint) local P:= Array(1..0), p; for p do if gmp_isprime(p) then i++; P,= p fi until i=n; [seq](P) end proc : Nprimes_indices:= proc(n::posint) local P, p, i:= 0; for p do if gmp_isprime(p) then P[p]:= ++i fi until i=n; [indices](P, 'nolist', 'indexorder') end proc : Nprimes_entries:= proc(n::posint) local P, p, i:= 0; for p do if gmp_isprime(p) then P[++i]:= p fi until i=n; [entries](P, 'nolist', 'indexorder') end proc : [ for P in Nprimes||(_do, _Array, _indices, _entries) do lprint(eval(P,1)); gc(); CodeTools:-Usage(P(2^17))[-1] od ]; Nprimes_do memory used=175.73MiB, alloc change=16.45MiB, cpu time=1.22s, real time=1.22s, gc time=0ns Nprimes_Array memory used=123.83MiB, alloc change=2.01MiB, cpu time=1.12s, real time=1.13s, gc time=0ns Nprimes_indices memory used=136.72MiB, alloc change=2.01MiB, cpu time=1.24s, real time=1.23s, gc time=0ns Nprimes_entries memory used=136.77MiB, alloc change=1.00MiB, cpu time=1.23s, real time=1.24s, gc time=0ns               [1742537, 1742537, 1742537, 1742537] </pre> Yes, ListBuffer is obsolete. And I think that the code above shows that your argument from several months ago about for loops being inefficient (based on your misreading of a poorly written and out-of-date help-page passage) is incorrect. The latest comments added to the Post, ListBuffer, a procedure for efficiently building arbitrarily sized lists 205497 Fri, 22 Sep 2023 09:59:01 Z Carl Love Carl Love Performance-bound guarantees? http://www.mapleprimes.com/posts/43257-ListBuffer-A-Procedure-For-Efficiently?ref=Feed:MaplePrimes:ListBuffer, a procedure for efficiently building arbitrarily sized lists:Comments#comment205499 <a href="/posts/43257-ListBuffer-A-Procedure-For-Efficiently#comment205497">@Carl Love</a> Thanks for your clarification.  Though "exprseq" is not a valid type, I'd like to know if the `,=` operation for an existing expression sequence (not a 1-dimensional rtable) is potentially inefficient. In Maple, "set" is a immutable structure, so the `union=` manipulation can be less efficient when incrementally building up the large set from its members. Will the use of `,=` add a significant amount of processing time to certain computations as well? The latest comments added to the Post, ListBuffer, a procedure for efficiently building arbitrarily sized lists 205499 Fri, 22 Sep 2023 14:47:23 Z sursumCorda sursumCorda