To make matters worse:
- It is harder to know your total memory usage if you have more on the
stack: it just magically goes down and overwrites whatever is already
there. A malloc atleast has a way of signalling failure: the NULL pointer
- On systems with caches (e.g. the cortex M7 in the ATSAME70 I currently
use) your timing will get less predictable as you might get different
timing for the same functions depending on wherever you stack pointer
happened to be. (Also think about where your stack will be during an
interrupt)
On 06/11/2018 05:41 PM, Bruce Perens wrote:
> Hi Sumek,
>
> Codec2 for embedded platforms is definitely in need of size
> optimization by *removing unused code for your chosen modes,* and
> speed optimization by *optimizing the floating-point calculation.*
>
> I think you might be wasting your time by pursuing structure and
> malloc() optimizations, though. Consider what happens when you remove
> malloc and place a variable on the stack. Instead of indexing through
> the heap pointer, you are indexing through the stack pointer. You
> don't see the stack pointer in the C code, but it's there. The
> instructions will probably be very similar, especially on ARM, you can
> check this using the -S flag of the compiler. When optimizing,
> /always/ use -S to look at the instructions generated by the compiler,
> this will show when an optimization is /really/ an optimization.
>
> Similarly, removing a struct and using a local variable would still
> index through the stack pointer.
>
> The second problem with removing malloc() and structs is that it makes
> it less likely that your work could be returned to David's codec2 sources.
>
> Thanks
>
> Bruce
>
> On Mon, Jun 11, 2018 at 1:00 AM, sumek.wi via Freetel-codec2
> <freetel-codec2@lists.sourceforge.net
> <mailto:freetel-codec2@lists.sourceforge.net>> wrote:
>
> Hi,
>
>
> The reduced I said is program size. Also, I removed malloc and
> struct to make the program
>
> as simple as possible for embedded systems, and it also reduce the
> execute time by not
>
> indexing pointer.
>
>
> I used gcc on CodeLite, I don't know why it doesn't remove
> unreferenced much. Probably
>
> it is in debug mode.
>
>
> Sumek.
>
> ------------------------------------------------------------------------
> *From:* Danilo Beuche <danilo.beu...@gmx.net
> <mailto:danilo.beu...@gmx.net>>
> *Sent:* Monday, June 11, 2018 12:06:54 PM
> *To:* freetel-codec2@lists.sourceforge.net
> <mailto:freetel-codec2@lists.sourceforge.net>
> *Subject:* Re: [Freetel-codec2] noob in voice coding asking for
> help about Codec2 decoder.
>
>
> Hi,
>
> btw, using the gcc's -flto during compiling and linking does a
> great job of removing unused data and functions. Basically the gcc
> breaks up every file into individual linkable elements (each
> global variable and functions becomes an independent linkage
> element) and anything not referenced anywhere simply disappears
> from the final binary. Of course there is a lot more going on with
> -flto (LTO stands for link time optimization) but one of the side
> effects of using LTO is this removal of unreferenced elements from
> binary code.
>
> Other compilers have similar "tricks".
>
> Regards,
> Danilo
>
> On 11.06.2018 03:19, Bruce Perens wrote:
>> Hi Sumek,
>>
>> I am curious about your memory saving strategy. Specifically, why
>> using the stack vs. malloc() would result in a significant memory
>> savings, and how removing structs would result in a significant
>> memory savings.
>>
>> Perhaps you mean you are removing /unused /ones?
>>
>> Or is there something about the Windows compiler I don't understand?
>>
>> Thanks
>>
>> Bruce
>>
>> On Sun, Jun 10, 2018 at 1:40 PM, David Rowe <da...@rowetel.com
>> <mailto:da...@rowetel.com>> wrote:
>>
>> Hi Sumek,
>>
>> Oh I have one question, do you know if we can reduce the
>> size of codebook especially lsp_cbjvm
>>
>>
>> Many of those tables aren't used, so just link in the ones
>> you need to support the Codec 2 modes you would like to use.
>>
>> Cheers,
>>
>> David
>>
>>
>>
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>>
>>
>>
>> --
>> Bruce Perens K6BP - CEO, Legal Engineering
>> Standards committee chair, license review committee member,
>> co-founder, Open Source Initiative
>> President, Open Research Institute; Board Member, Fashion Freedom
>> Initiative.
>>
>>
>>
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>
>
> --
> Bruce Perens K6BP - CEO, Legal Engineering
> Standards committee chair, license review committee member,
> co-founder, Open Source Initiative
> President, Open Research Institute; Board Member, Fashion Freedom
> Initiative.
>
>
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