D Mir: standard deviation speed

[9il]

On Wednesday, 15 July 2020 at 06:00:46 UTC, tastyminerals wrote:
> On Wednesday, 15 July 2020 at 02:08:48 UTC, 9il wrote:
>> On Tuesday, 14 July 2020 at 19:04:45 UTC, tastyminerals wrote:
>>> @fastmath private double sd0(T)(Slice!(T*, 1) flatMatrix)
>>
>> @fastmath shouldn't be really used with summation algorithms 
>> except the `"fast"` version of them. Otherwise, they may or 
>> may not behave like "fast".
>
> Good to know. So, it's fine to use it with sum!"fast" but 
> better avoid it for general purposes.

They both are more precise by default.