[PD] better tabread4~

[cyrille henry]

Matt Barber a écrit :
> Cyrille,
> 
> Could you try this optimization for the tabread6c~ I threw together?
> It uses the same general notation as the tab4c~ suite:
> 
> 	t_sample a3plusa4plusa5 = 0.25f*c+0.125f*e-0.3333333f*d-0.04166667*a;
> 	t_sample fminusa = f-a;
> 	t_sample eminusb = e-b;
> 	t_sample dminusc = d-c;
> 
> 	a5 = 0.2083333f*((fminusa-5.f*eminusb+10.f*dminusc));
> 	a4 = 2.6666667f*eminusb-0.5f*fminusa-5.5f*dminusc-a3plusa4plusa5;
> 	a3 = a3plusa4plusa5-a4-a5;
> 	a2 = 0.6666667f*(d+b)-0.04166667f*(a+e)-1.25f*c;
> 	a1 = 0.6666667f*(d-b)+0.08333333f*(a-e);
> 	a0 = c;
> 
> 	*out++ =  ((((a5 * frac + a4 ) * frac + a3) * frac + a2) * frac + a1)
> * frac + a0;
> 
ok

> 
> I've tested it and I think it works...  I count 20 *'s and 25 +'s = 45
> ops vs. 31 *'s, and 27 +'s = 58 ops (if the fractions were written out
> as decimals).
The compiler should be intelligent enough to convert (2./3.) to 0.666... but using more precision than the 8 digit you write in your code.
so i prefer the exact fraction than approximation...

cyrille


> 
> Thanks,
> 
> Matt
> 
> 
>> Date: Tue, 08 Jul 2008 18:35:51 +0200
>> From: cyrille henry <cyrille.henry at la-kitchen.fr>
>> Subject: Re: [PD] better tabread4~
>> To: Charles Henry <czhenry at gmail.com>
>> Cc: pd-list at iem.at
>> Message-ID: <48739767.3050400 at la-kitchen.fr>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>> hello Chuck,
>>
>> i tested this. (and commited)
>> i think tabread6c~ is a bit better than tabread4c~. but differences are more smaller
>>
>> thx
>>
>> Cyrille
>>
>>
>> Charles Henry a ?crit :
>>> On Sat, Jun 28, 2008 at 6:43 AM, cyrille henry
>>> <cyrille.henry at la-kitchen.fr> wrote:
>>>
>>>
>>> The coefficients used in this scheme are
>>>
>>> a0= Y[0]
>>> a1= 1/12*Y[-2] - 2/3*Y[-1] + 2/3*Y[1] - 1/12*Y[2]
>>> a2= -1/24*Y[-2] + 2/3*Y[-1] - 5/4*Y[0] + 2/3*Y[1] - 1/24*Y[2]
>>> a3= -3/8*Y[-2] + 13/8*Y[-1] - 35/12*Y[0] + 11/4*Y[1] - 11/8*Y[2] + 7/24*Y[3]
>>> a4= 13/24*Y[-2] - 8/3*Y[-1] + 21/4*Y[0] - 31/6*Y[1] + 61/24*Y[2] - 1/2*Y[3]
>>> a5= -5/24*Y[-2] + 25/24*y[-1] - 25/12*Y[0] + 25/12*Y[1] - 25/24*Y[2] + 5/24*Y[3]
>>>
> 
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