MAD 0.15 Accuracy

Hi!

I tested my implementation of some math function for MAD 0.15 library.
And I have found this:

function
mad_fixed_t III_requantize(unsigned int value, signed int exp)
in layer3.c file

input
value=8
exp=-23;

that means
8^(4/3)*2(-5.75)
correct?

result obtained by
mad_f_todouble(requantized)is

0.297241

but calculator says
>> 8^(4/3)*2^(-5.75)
ans = 0.29730177875068

for Q15 format its means ~2 bits difference.
>>(0.29730177875068-0.29724100000000)*32768
ans = 1.99159810228230

my Q15 arithmetics gives:
9743/32768=0.29733276367188
>>(0.29730177875068-0.29733276367188)*32768
ans = -1.01531389788215

 -1 bit difference

 And total difference between MAD math and my = 3 bits!

Maybe I have to compare my math not with MAD - but with some float point
implementation?

 
-- 
Best regards,
 Grigory                          mailto:[email protected]