Hi,
Expression template can be used for the implementation of simple
operators without using temporaries (e.g. the ones in the book C++
Template).
I'm wondering whether expression template is useful for the
convolution operation.
For example, I have two arrays a1 and a2. To compute the convolution
between them I need to compute the FFT of both of them, which shall be
stored in two temporary arrays. These arrays then shall be multiplied
and FFT back, which also need a temporary arrays. There are totally
three temporary arrays.
It seems that expression template would not reduce the number of
temporary arrays. Are there any better way to reduce the temporaries?
Thanks,
Peng
12  2515 
On Oct 19, 7:49*pm, Peng Yu <PengYu...@gmai l.comwrote:
Hi,
Expression template can be used for the implementation of simple
operators without using temporaries (e.g. the ones in the book C++
Template).
I'm wondering whether expression template is useful for the
convolution operation.
For example, I have two arrays a1 and a2. To compute the convolution
between them I need to compute the FFT of both of them, which shall be
stored in two temporary arrays. These arrays then shall be multiplied
and FFT back, which also need a temporary arrays. There are totally
three temporary arrays.
It seems that expression template would not reduce the number of
temporary arrays. Are there any better way to reduce the temporaries?
Thanks,
Peng
If you want to reduce temporaries, try to read Alexandrescu's mojo
code. Expression templates are too advanced for what you need to do,
so it may not pay the time in coding it. Hope it helps,
aa
On 20 Okt., 05:53, aaragon <alejandro.ara. ..@gmail.comwro te:
>
If you want to reduce temporaries, try to read Alexandrescu's mojo
code. Expression templates are too advanced for what you need to do,
so it may not pay the time in coding it. Hope it helps,
aa
Hm, I didn't know the term "mojo". Just search-machined for it and
found:
- http://www.ddj.com/database/184403855
I'll have a look into this. Thanks for hint.
-- Maik
On Oct 20, 5:01*am, Maik <Beckmann.M...@ googlemail.comw rote:
On 20 Okt., 05:53, aaragon <alejandro.ara. ..@gmail.comwro te:
If you want to reduce temporaries, try to read Alexandrescu's mojo
code. Expression templates are too advanced for what you need to do,
so it may not pay the time in coding it. Hope it helps,
aa
Hm, I didn't know the term "mojo". *Just search-machined for it and
found:
*-http://www.ddj.com/database/184403855
I'll have a look into this. Thanks for hint.
-- Maik
That is very easy to implement after you understand how it works. Good
luck,
aa
On 20 Okt., 02:49, Peng Yu <PengYu...@gmai l.comwrote:
I'm wondering whether expression template is useful for the
convolution operation.
Calculating the FFT and inverse FFT can be done in-place. No
temporaries needed. If you want to keep the original signals 'a1' and
'a2' you can do it with TWO temporaries:
<pseudo code>
t1 = a1; fft(t1); // copy 'a1' to 't1' and do an FFT on it
t2 = a2; fft(t2); // copy 'a2' to 't2' and do an FFT on it
t1 *= t2; // element-wise complex product
ifft(t1); // t1 will contains the (circular-)convolution result
</pseudo code>
I don't think that expression templates can help here.
Cheers,
SG
On Oct 20, 2:11 pm, aaragon <alejandro.ara. ..@gmail.comwro te:
On Oct 20, 5:01 am, Maik <Beckmann.M...@ googlemail.comw rote:
On 20 Okt., 05:53, aaragon <alejandro.ara. ..@gmail.comwro te:
If you want to reduce temporaries, try to read Alexandrescu's mojo
code. Expression templates are too advanced for what you need to do,
so it may not pay the time in coding it. Hope it helps,
aa
Hm, I didn't know the term "mojo". Just search-machined for it and
found:
-http://www.ddj.com/database/184403855
I'll have a look into this. Thanks for hint.
-- Maik
That is very easy to implement after you understand how it works. Good
luck,
Hi,
It is too long to read the webpage. Can somebody explain in a brief
way what the main point is and what the major steps to use mojo?
Thanks,
Peng
Peng Yu wrote:
On Oct 20, 2:11 pm, aaragon <alejandro.ara. ..@gmail.comwro te:
>On Oct 20, 5:01 am, Maik <Beckmann.M...@ googlemail.comw rote:
[...]
>> -http://www.ddj.com/database/184403855
I'll have a look into this. Thanks for hint.
-- Maik
That is very easy to implement after you understand how it works. Good
luck,
Hi,
It is too long to read the webpage. Can somebody explain in a brief
way what the main point is and what the major steps to use mojo?
It's main point is to avoid unnecessary copying. It does so by
"stealing" the data from temporary objects instead. This is what
rvalue references will be in C++0x.
If you want to use it to write fast code, you won't get around
reading and understanding it.
Thanks,
Peng
Schobi
On Oct 21, 3:33 am, Hendrik Schober <spamt...@gmx.d ewrote:
Peng Yu wrote:
On Oct 20, 2:11 pm, aaragon <alejandro.ara. ..@gmail.comwro te:
On Oct 20, 5:01 am, Maik <Beckmann.M...@ googlemail.comw rote:
[...]
> -http://www.ddj.com/database/184403855
I'll have a look into this. Thanks for hint.
-- Maik
That is very easy to implement after you understand how it works. Good
luck,
Hi,
It is too long to read the webpage. Can somebody explain in a brief
way what the main point is and what the major steps to usemojo?
It's main point is to avoid unnecessary copying. It does so by
"stealing" the data from temporary objects instead. This is what
rvalue references will be in C++0x.
If you want to use it to write fast code, you won't get around
reading and understanding it.
So it is still quite useful even after 5 years since it was written,
and no other technique beats it right now? Is it a widely used and
necessary technique today?
Thanks,
Peng
Peng Yu wrote:
On Oct 21, 3:33 am, Hendrik Schober <spamt...@gmx.d ewrote:
>Peng Yu wrote:
>>On Oct 20, 2:11 pm, aaragon <alejandro.ara. ..@gmail.comwro te:
On Oct 20, 5:01 am, Maik <Beckmann.M...@ googlemail.comw rote:
[...]
-http://www.ddj.com/database/184403855
I'll have a look into this. Thanks for hint.
-- Maik
That is very easy to implement after you understand how it works. Good
luck,
Hi,
It is too long to read the webpage. Can somebody explain in a brief
way what the main point is and what the major steps to usemojo?
It's main point is to avoid unnecessary copying. It does so by
"stealing" the data from temporary objects instead. This is what
rvalue references will be in C++0x.
If you want to use it to write fast code, you won't get around
reading and understanding it.
So it is still quite useful even after 5 years since it was written,
and no other technique beats it right now? Is it a widely used and
necessary technique today?
From what I read, rvalue references seem to be better, but
until you get your hands on a compiler that has them, Andrei's
code and ideas are most likely the best you can get.
Peng
Schobi
On Oct 21, 11:28 am, Hendrik Schober <spamt...@gmx.d ewrote:
Peng Yu wrote:
On Oct 21, 3:33 am, Hendrik Schober <spamt...@gmx.d ewrote:
Peng Yu wrote:
On Oct 20, 2:11 pm, aaragon <alejandro.ara. ..@gmail.comwro te:
On Oct 20, 5:01 am, Maik <Beckmann.M...@ googlemail.comw rote:
[...]
-http://www.ddj.com/database/184403855
I'll have a look into this. Thanks for hint.
-- Maik
That is very easy to implement after you understand how it works. Good
luck,
Hi,
It is too long to read the webpage. Can somebody explain in a brief
way what the main point is and what the major steps to usemojo?
It's main point is to avoid unnecessary copying. It does so by
"stealing" the data from temporary objects instead. This is what
rvalue references will be in C++0x.
If you want to use it to write fast code, you won't get around
reading and understanding it.
So it is still quite useful even after 5 years since it was written,
and no other technique beats it right now? Is it a widely used and
necessary technique today?
From what I read, rvalue references seem to be better, but
until you get your hands on a compiler that has them, Andrei's
code and ideas are most likely the best you can get.
I see a proposal to add rvalue reference in the standard. Is it in the
standard now? Is there any compiler that supports it?
Thanks,
Peng This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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