[FFmpeg-devel] [PATCH] Move MLP's dot product to DSPContext

[Michael Niedermayer]

On Sun, Apr 19, 2009 at 10:10:05PM -0300, Ramiro Polla wrote:
> Hi,
> 
> Attached file move MLP's dot product to DSPContext. The filter order
> is a maximum of 8, and in the rematrix stage it's a maximum of 5+2
> channels for MLP and 7+0 channels for TrueHD, so it all fits in 8
> (hopefully) optimized functions.

the functions are too small, the call overhead is too much
1-8 multiplicatons and 1-8 additions is not enough ...


[...]

> static int64_t mlp_dotproduct_c(int32_t *state, int32_t *coeffs, int order)

the arguments should be const


> {
>     int64_t accum = 0;
> 
>     while (order--)
>         accum += (int64_t) *state++ * *coeffs++;

switch(order){
case 8: accum  = (int64_t) *state++ * *coeffs++;
case 7: accum += (int64_t) *state++ * *coeffs++;
case 6: accum += (int64_t) *state++ * *coeffs++;
case 5: accum += (int64_t) *state++ * *coeffs++;
case 4: accum += (int64_t) *state++ * *coeffs++;
case 3: accum += (int64_t) *state++ * *coeffs++;
case 2: accum += (int64_t) *state++ * *coeffs++;
case 1: accum += (int64_t) *state   * *coeffs  ;
case 0:
}

also state[i] * coeffs[i]; i++
could be tried

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Dictatorship naturally arises out of democracy, and the most aggravated
form of tyranny and slavery out of the most extreme liberty. -- Plato
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