Speed kills

cym13 via Digitalmars-d digitalmars-d at puremagic.com
Wed Mar 9 05:42:40 PST 2016


On Wednesday, 9 March 2016 at 13:26:45 UTC, Andrei Alexandrescu 
wrote:
> On 03/08/2016 09:14 AM, ixid wrote:
>> Since I posted this thread I've learned std.algorithm.sum is 4 
>> times
>> slower than a naive loop sum. Even if this is for reasons of 
>> accuracy
>> this is exactly what I am talking about- this is a hidden 
>> iceberg of
>> terrible performance that will reflect poorly on D. That's so 
>> slow the
>> function needs a health warning.
>
> Whoa. What's happening there? Do we have anyone on it? -- Andrei

They just don't do the same thing, sum() uses pairwise summation 
which is safer as I understand it. Corresponding issue: 
https://issues.dlang.org/show_bug.cgi?id=15722


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