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Posted to dev@openoffice.apache.org by Andre Fischer <aw...@gmail.com> on 2014/01/21 08:57:19 UTC
Precompiled headers
Yesterday I was asked whether the use of precompiled headers had any
benefit on the compilation speed. I thought the answer would be yes but
I was not sure. So I did some tests. And the difference is huge. I
compiled sw/ with
make -sr -j8
on a i7 s2720 (2.2GHz), 8GB Ram laptop.
Without precompiled headers that takes a little over 19 minutes. With
precompiled headers that drops down to a little over 10 minutes. That
is a reduction of almost 50%.
Maybe we should think to
a) make the --enable-pch configure switch the default and
b) remove the word "experimental" from its description.
Regards,
Andre
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Re: Precompiled headers
Posted by Oliver-Rainer Wittmann <or...@googlemail.com>.
Hi,
On 21.01.2014 08:57, Andre Fischer wrote:
> Yesterday I was asked whether the use of precompiled headers had any
> benefit on the compilation speed. I thought the answer would be yes but
> I was not sure. So I did some tests. And the difference is huge. I
> compiled sw/ with
>
> make -sr -j8
>
> on a i7 s2720 (2.2GHz), 8GB Ram laptop.
> Without precompiled headers that takes a little over 19 minutes. With
> precompiled headers that drops down to a little over 10 minutes. That
> is a reduction of almost 50%.
>
I can confirm Andre's findings.
That is the reason why I had the precompiled headers enabled in all of
my AOO build environments which I use for development under Windows.
> Maybe we should think to
> a) make the --enable-pch configure switch the default and
+1
> b) remove the word "experimental" from its description.
+10
Best regards, Oliver.
>
> Regards,
> Andre
>
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Re: Precompiled headers
Posted by Issac Goldstand <is...@volo-net.com>.
On 21/01/2014 13:56, Andre Fischer wrote:
> On 21.01.2014 09:25, Issac Goldstand wrote:
>> On 21/01/2014 10:09, Andre Fischer wrote:
>>> On 21.01.2014 08:57, Andre Fischer wrote:
>>>> Yesterday I was asked whether the use of precompiled headers had any
>>>> benefit on the compilation speed. I thought the answer would be yes
>>>> but I was not sure. So I did some tests. And the difference is
>>>> huge. I compiled sw/ with
>>>>
>>>> make -sr -j8
>>>>
>>>> on a i7 s2720 (2.2GHz), 8GB Ram laptop.
>>> One important addition: precompiled headers are only supported on
>>> Windows (my experiment took place on Windows7). I guess the other
>>> systems are fast enough without precompiled headers.
>>>
>> Also, I'm not an expert, but I think that there's a difference for
>> release artifacts whether or not you compile with PCH. I know that the
>> chromium project, for example, recommends PCH for debug builds, but for
>> final releases, removing PCH is a big part of the optimizations...
>
> Good to know. Do you have any pointers?
> -Andre
I don't :(. I only remember having heard about the performance hit
once, but lack of Googled information on the subjects suggests that I
may be wrong/outdated.
About the chromium project, see this link
https://code.google.com/p/chromium/wiki/WindowsPrecompiledHeaders which
mentions the bit of gospel I mentioned above (by default for
non-official builds) without really explaining why the release build
doesn't use it by default.
Sorry I can't be more helpful,
Issac
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Re: Precompiled headers
Posted by Andre Fischer <aw...@gmail.com>.
On 21.01.2014 09:25, Issac Goldstand wrote:
> On 21/01/2014 10:09, Andre Fischer wrote:
>> On 21.01.2014 08:57, Andre Fischer wrote:
>>> Yesterday I was asked whether the use of precompiled headers had any
>>> benefit on the compilation speed. I thought the answer would be yes
>>> but I was not sure. So I did some tests. And the difference is
>>> huge. I compiled sw/ with
>>>
>>> make -sr -j8
>>>
>>> on a i7 s2720 (2.2GHz), 8GB Ram laptop.
>> One important addition: precompiled headers are only supported on
>> Windows (my experiment took place on Windows7). I guess the other
>> systems are fast enough without precompiled headers.
>>
> Also, I'm not an expert, but I think that there's a difference for
> release artifacts whether or not you compile with PCH. I know that the
> chromium project, for example, recommends PCH for debug builds, but for
> final releases, removing PCH is a big part of the optimizations...
Good to know. Do you have any pointers?
-Andre
>
> Issac
>
>
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Re: Precompiled headers
Posted by Issac Goldstand <is...@volo-net.com>.
On 21/01/2014 10:09, Andre Fischer wrote:
> On 21.01.2014 08:57, Andre Fischer wrote:
>> Yesterday I was asked whether the use of precompiled headers had any
>> benefit on the compilation speed. I thought the answer would be yes
>> but I was not sure. So I did some tests. And the difference is
>> huge. I compiled sw/ with
>>
>> make -sr -j8
>>
>> on a i7 s2720 (2.2GHz), 8GB Ram laptop.
>
> One important addition: precompiled headers are only supported on
> Windows (my experiment took place on Windows7). I guess the other
> systems are fast enough without precompiled headers.
>
Also, I'm not an expert, but I think that there's a difference for
release artifacts whether or not you compile with PCH. I know that the
chromium project, for example, recommends PCH for debug builds, but for
final releases, removing PCH is a big part of the optimizations...
Issac
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Re: Precompiled headers
Posted by Andre Fischer <aw...@gmail.com>.
On 21.01.2014 08:57, Andre Fischer wrote:
> Yesterday I was asked whether the use of precompiled headers had any
> benefit on the compilation speed. I thought the answer would be yes
> but I was not sure. So I did some tests. And the difference is huge.
> I compiled sw/ with
>
> make -sr -j8
>
> on a i7 s2720 (2.2GHz), 8GB Ram laptop.
One important addition: precompiled headers are only supported on
Windows (my experiment took place on Windows7). I guess the other
systems are fast enough without precompiled headers.
> Without precompiled headers that takes a little over 19 minutes. With
> precompiled headers that drops down to a little over 10 minutes. That
> is a reduction of almost 50%.
>
> Maybe we should think to
> a) make the --enable-pch configure switch the default and
> b) remove the word "experimental" from its description.
>
> Regards,
> Andre
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