Performance of tables slower than built in?

[Basile B.]

On Wednesday, 22 May 2019 at 08:25:58 UTC, Basile B. wrote:
> On Wednesday, 22 May 2019 at 00:22:09 UTC, JS wrote:
>> I am trying to create some fast sin, sinc, and exponential 
>> routines to speed up some code by using tables... but it seems 
>> it's slower than the function itself?!?
>>
>> [...]
>
> Hi, lookup tables ARE faster but the problem you have here, and 
> I'm surprised that nobody noticed it so far, is that YOUR 
> SWITCH LEADS TO A RUNTIME STRING COMPARISON AT RUNTIME. Just 
> replace it with a static if (Method = "Linear") { /*...*/} else 
> { /*...*/}

Oh no... I meant "==" obviously

> Also takes care to the type used. With DMD the implicit 
> coercion of float and double can lead to extra conversions.
>
> You'll directly see a 15% gain after refactoring the switch.