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Hi,
I just begin to learn DSP.Now I have a question about optimizing.And I hope to get your help.
There is a division in a loop as shown in the following(C64x):
...
for(i=0;i<n;i++)
{
...
a = b / 3;
...
}
The information of .asm says that




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On 7/28/05, wangfeng_scu@wang... <wangfeng_scu@wang...> wrote:
> Hi,
> I just begin to learn DSP.Now I have a question about optimizing.And I hope to get your help.

...

> The information of .asm says that

You message is incomplete.Can you repost the information ?

--Bhooshan





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Hi Bhooshan-

> On 7/28/05, wangfeng_scu@wang... <wangfeng_scu@wang...> wrote:
> > Hi,
> > I just begin to learn DSP.Now I have a question about optimizing.And I hope to get your help.
>
> ...
>
> > The information of .asm says that
>
> You message is incomplete.Can you repost the information ?

Below is the rest of Wang Feng's info, plus his question.

-Jeff The infomation of .asm says that "Pipeline disqualified:Loop contains
a call".

My question is: How can I improve this division in order to meet the
pipeline qualification?





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Hi,

it is not clear what function is called, but you can try to inline the
function.

HTH Gustl

wangfeng_scu@wang... wrote:
> Hi,
> I just begin to learn DSP.Now I have a question about optimizing.And I hope to get your help.
> There is a division in a loop as shown in the following(C64x):
> ...
> for(i=0;i<n;i++)
> {
> ...
> a = b / 3;
> ...
> }
> The information of .asm says that



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Hi,

I think that your problem is the division by 3, and as we know the C64x is a fixed point DSP. So when you use a division by 3, it tries to call some functions like __divf and __frcdivf to do this division. So the solution is to write your equation otherwise for example:
a = (b * Y)>>X;
It means we replace 1/3 with Y>>X    ==>  Y =  (2^X)/3
Try to choose X between 20 and 30 for exp X = 22  ==>  Y = 1398101
But you should pay attention when you do the multiplication between b and Y, the result can be double and not int.
And also this solution is only for a fixed point results, it means the result of “a” isn't float.

Kindest regards, 
Anouar Bernhard Gustl Bauer wrote:

Hi,
it is not clear what function is called, but you can try to inline the function.
HTH Gustl
w...@yahoo.com.cn wrote:

Hi,
I just begin to learn DSP.Now I have a question about optimizing.And I hope to get your help.
There is a division in a loop as shown in the following(C64x):
...
for(i=0;i<n;i++)
{
...
a = b / 3;
...
}
The information of .asm says that 

(You need to be a member of c6x -- send a blank email to c6x-subscribe@yahoogroups.com )