Talk:Rare numbers: Difference between revisions
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→Tweaks, C++: Further syntax-highlighting fixes
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== the 1<sup>st</sup> REXX version ==
This is the 1<sup>st</sup> REXX version, before all the optimizations were added:
<syntaxhighlight lang="rexx">
numeric digits 20; w= digits() + digits() % 3 /*ensure enough decimal digs for calcs.*/
parse arg many start . /*obtain optional argument from the CL.*/
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if _>=0 then do; x= _; $= $ + q
end
end /*while q>1*/; return $
</syntaxhighlight>
Pretty simple, but slow as molasses in January.
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of ''rare'' numbers) within Shyam Sunder Gupta's
<br>[http://www.shyamsundergupta.com/rare.htm <u>webpage</u>] have been incorporated in this REXX program.
<
numeric digits 20; w= digits() + digits() % 3 /*ensure enough decimal digs for calcs.*/
parse arg many start . /*obtain optional argument from the CL.*/
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if _>=0 then do; x= _; $= $ + q
end
end /*while q>1*/; return $</
Still pretty sluggish, like molasses in March.
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square containing the combination 9 or 14 as the first/last digit.
<
import (
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bStart = time.Now() // restart block timing
}
}</
{{out}}
Results on the core i7-7700 @ 3.6Ghz.
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:I've also updated Nigel's C++ version with the same tweaks:
<
#include <functional>
#include <bitset>
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int main(){
Rare(19);
}</
:Compiling this with g++ brings the overall execution time down from 30 to 21 minutes in round figures. So the figures for clang or mingw may well come in at below 10 minutes now.
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== Tweaks, C++ ==
Wringing out some more performance here, just over 5 minutes for 19 digits by themselves, and just over 6 minutes for digits 2 thru 19. See the code comments for details on what was tweaked. Curiously, I found that the g++ version executes faster than the clang++ version. Compiler arguments used: <code>g++ rare.cpp -o rare.exe -std=c++17 -O3</code><br/>Curious to see if it can go faster on a different platform - But the original executed faster on g++ than clang++ for me on my platform too. Perhaps I don't have clang++ set up the same as others?
<
/*
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printf("%4s %19s %11s %10s %5s %11s %9s\n", "nth", "forward", "rt.sum", "rt.diff", "digs", "block.et", "total.et");
for (int nd = 2; nd <= max; nd++) Rare(int(nd));
}</
{{out}}
Results on the core i7-7700 @ 3.6Ghz.
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</pre>
--[[User:Nigel Galloway|Nigel Galloway]] ([[User talk:Nigel Galloway|talk]]) 14:09, 4 January 2021 (UTC)
*
*
:::Thank you for the code review and adopting some of the tweaks I presented. Good fix for my awkward handling of digits 2-11. I agree about the pair construction, I only removed it to speed up my C# translation, which was slightly impacting performance (perhaps due to an awkward translation on my part.)<br><br>
:::I agree that digit '5' ought to be considered in the "diff" side. Even though it doesn't contribute to any solution in the ''Int64'' range, if ''Int128'' ever becomes part of C++, your program should be easily extended to the point where checking "diff 5" will contribute a solution. My decision to omit checking '5' was for performance reasons since we are constricted to ''Int64''.--[[User:Enter your username|Enter your username]] ([[User talk:Enter your username|talk]]) 00:01, 25 January 2021 (UTC)
== 21+ digit rare numbers ==
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