Author |
Topic: Letting GCC do the hard work (Read 1780 times) |
|
rtr
Guest
|
 |
Re: Letting GCC do the hard work
« Reply #8 on: Aug 17th, 2014, 10:32am » |
|
on Aug 17th, 2014, 08:13am, David Williams wrote:| This kind of performance is convincing me that hybridizing BB4W and C/C++ code is the way to go (for me personally). |
|
Performance (if by that you mean speed) is not a good reason to go down the GCC route. Even though the code generators in modern compilers are very good, you will almost always be able to do better with hand-crafted assembler.
That is especially true when you are not targeting a particular CPU architecture, but want the code to run on a wide range of machines. In that case much of the clever code-optimising for a specific architecture, that GCC can do very well, will benefit some machines at the expense of others.
If you are compiling with the -march=native switch and then testing your code on the same machine you are getting a misleading impression of performance (unless of course you want to go down the route of including machine code for a range of different architectures and choosing the best one at run time).
Where using C does admittedly have advantages is in speed and ease of coding, and especially in time taken debugging. If those are the issues that most concern you, then fine.
Richard.
|
|
 Logged
|
|
|
|
David Williams
Developer
member is offline
meh
Gender: 
Posts: 452
|
|
Re: Letting GCC do the hard work
« Reply #9 on: Aug 17th, 2014, 11:38am » |
|
on Aug 17th, 2014, 10:32am, Richard Russell wrote:| If you are compiling with the -march=native switch and then testing your code on the same machine you are getting a misleading impression of performance [...] |
|
Yes, I did use that switch and when after uploading the EXE for public consumption, I discovered that it crashed my 32-bit XP-based laptop (which I hardly use now!). I suspect my use of -march=native caused GCC to generate 64-bit code since the laptop the code was compiled on is a 64-bit machine. Lesson learned.
Re-compiling the vector balls demo without the aforementioned switch results in the code working on the 32-bit laptop, although the frame rate isn't as high as on the compilation machine (which is a little faster anyway, I think).
Quote:| Where using C does admittedly have advantages is in speed and ease of coding, and especially in time taken debugging. If those are the issues that most concern you, then fine. |
|
For the vast majority of my 'applications', the speed of GCC's generated ASM code suffices (and in some cases, has exceeded the speed of my hand-written ASM code, which isn't too surprising!). I won't be touching -- or rather, writing -- assembler code again unless my life depends on it.
David.
--
|
|
Logged
|
|
|
|
|
