digitalmars.D.bugs - [Issue 12446] New: std.parallelism.amap prefer iteration to indexing
- d-bugmail puremagic.com (20/20) Mar 23 2014 https://d.puremagic.com/issues/show_bug.cgi?id=12446
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https://d.puremagic.com/issues/show_bug.cgi?id=12446 Summary: std.parallelism.amap prefer iteration to indexing Product: D Version: D2 Platform: All OS/Version: All Status: NEW Severity: enhancement Priority: P2 Component: Phobos AssignedTo: safety0ff.bugz gmail.com ReportedBy: safety0ff.bugz gmail.com 13:36:07 PDT --- Currently std.parallelism.amap uses the random access range primitives instead of the input range primitives to traverse the per-thread slices. This matters when random access is more expensive than iteration. Iteration, if properly implemented, should always at least as fast as indexing. -- Configure issuemail: https://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Mar 23 2014
d-bugmail puremagic.com https://d.puremagic.com/issues/show_bug.cgi?id=12446 13:54:09 PDT ---This matters when random access is more expensive than iteration. Iteration, if properly implemented, should always at least as fast as indexing.It occurred to me that the cost of slicing a range could be disproportionate to indexing. Are there any use cases where this is true? -- Configure issuemail: https://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Mar 23 2014
https://d.puremagic.com/issues/show_bug.cgi?id=12446 safety0ff.bugz <safety0ff.bugz gmail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |pull 14:37:56 PDT --- https://github.com/D-Programming-Language/phobos/pull/2042 -- Configure issuemail: https://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Mar 23 2014
https://d.puremagic.com/issues/show_bug.cgi?id=12446 Andrei Alexandrescu <andrei erdani.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |andrei erdani.com PDT --- I think the differences should be negligible among the two approaches. -- Configure issuemail: https://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Mar 23 2014
https://d.puremagic.com/issues/show_bug.cgi?id=12446 PDT --- ... But there's always a way to test by measuring :o). Try it on a few typical ranges. ("Typical" == cost of random access, if offered, shouldn't be onerous.) -- Configure issuemail: https://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Mar 23 2014
https://d.puremagic.com/issues/show_bug.cgi?id=12446
15:26:51 PDT ---
... But there's always a way to test by measuring :o). Try it on a few typical
ranges. ("Typical" == cost of random access, if offered, shouldn't be onerous.)
It's not typical array-like random access ranges that will benefit, it's
atypical ones where iteration is simple but indexing is non-trivial.
For example, my "triangular" random access range which returns the tuples:
[0, 0], [1, 0], [1, 1], [2, 0], [2, 1], [2, 2], [3, 0], [3, 1], [3, 2], [3, 3]
Iteration is simple, but indexing involves solving a quadratic + some other
operations.
Even though one might not call this "onerous," there is still enough relative
difference for it to be noticeable.
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Mar 23 2014
https://d.puremagic.com/issues/show_bug.cgi?id=12446 Commits pushed to master at https://github.com/D-Programming-Language/phobos https://github.com/D-Programming-Language/phobos/commit/fc3cda0beb95d5164af5767c9f8134359968d294 Fix issue 12446 - std.parallelism.amap: prefer iteration to indexing https://github.com/D-Programming-Language/phobos/commit/35617d87b30a3bf17d3dc50bf41bac4c4627c12f Fix issue 12446 - std.parallelism.amap: prefer iteration to indexing -- Configure issuemail: https://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Mar 23 2014
https://d.puremagic.com/issues/show_bug.cgi?id=12446 safety0ff.bugz <safety0ff.bugz gmail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution| |FIXED -- Configure issuemail: https://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Mar 23 2014