Re: [FFmpeg-devel] [FFmpeg-cvslog] checkasm: test for abs_pow34

[James Almer <jamrial@gmail.com>]

On 1/23/2024 4:07 PM, Michael Niedermayer wrote:
> On Mon, Dec 11, 2023 at 04:42:26PM +0000, sunyuechi wrote:
>> ffmpeg | branch: master | sunyuechi <sunyuechi@iscas.ac.cn> | Tue Nov 28 14:08:12 2023 +0800| [1c3620b2bbe73db9239fcf605e8f535b58f03b86] | committer: Rémi Denis-Courmont
>>
>> checkasm: test for abs_pow34
>>
>> Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>
>>
>>> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=1c3620b2bbe73db9239fcf605e8f535b58f03b86
>> ---
>>
>>   tests/checkasm/Makefile    |  1 +
>>   tests/checkasm/aacencdsp.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++
>>   tests/checkasm/checkasm.c  |  3 ++
>>   tests/checkasm/checkasm.h  |  1 +
>>   tests/fate/checkasm.mak    |  3 +-
>>   5 files changed, 77 insertions(+), 1 deletion(-)
> [...]
>> +static void test_abs_pow34(AACEncContext *s) {
>> +#define BUF_SIZE 1024
>> +    LOCAL_ALIGNED_32(float, in, [BUF_SIZE]);
>> +
>> +    declare_func(void, float *, const float *, int);
>> +
>> +    randomize_float(in, BUF_SIZE);
>> +
>> +    if (check_func(s->abs_pow34, "abs_pow34")) {
>> +        LOCAL_ALIGNED_32(float, out, [BUF_SIZE]);
>> +        LOCAL_ALIGNED_32(float, out2, [BUF_SIZE]);
>> +
>> +        call_ref(out, in, BUF_SIZE);
>> +        call_new(out2, in, BUF_SIZE);
>> +
>> +        if (memcmp(out, out2, BUF_SIZE * sizeof(float)) != 0)
>> +            fail();
> 
> This is wrong if one of the functions is implemented in C
> C does not specify float to give bitexact results. Any equality check with
> float thats expected to end in a reproduceable outcome is generally wrong

Yes, that's why float_near_abs_eps_array() or float_near_ulp_array() 
should be used.

> 
> it also fails in practice
> 
> TEST    checkasm-aacencdsp
> Test checkasm-aacencdsp failed. Look at tests/data/fate/checkasm-aacencdsp.err for details.
> src/tests/Makefile:308: recipe for target 'fate-checkasm-aacencdsp' failed
> make: *** [fate-checkasm-aacencdsp] Error 1
> 
> checkasm: using random seed 2523748868
> SSE:
>     abs_pow34_sse (aacencdsp.c:55)
>   - aacencdsp.abs_pow34 [FAILED]
> checkasm: 1 of 1 tests have failed
> threads=1
> 
> thats on plain simple x86-32

Can you check if the following passes for x86-32?

> diff --git a/tests/checkasm/aacencdsp.c b/tests/checkasm/aacencdsp.c
> index 684c775862..7cc8a01158 100644
> --- a/tests/checkasm/aacencdsp.c
> +++ b/tests/checkasm/aacencdsp.c
> @@ -19,6 +19,7 @@
>   */
> 
>  #include <string.h>
> +#include <float.h>
> 
>  #include "libavutil/mem.h"
>  #include "libavutil/mem_internal.h"
> @@ -51,7 +52,7 @@ static void test_abs_pow34(AACEncContext *s) {
>          call_ref(out, in, BUF_SIZE);
>          call_new(out2, in, BUF_SIZE);
> 
> -        if (memcmp(out, out2, BUF_SIZE * sizeof(float)) != 0)
> +        if (!float_near_abs_eps_array(out, out2, FLT_EPSILON, BUF_SIZE))
>              fail();
> 
>          bench_new(out, in, BUF_SIZE);

That target tends to be pretty picky about the epsilon value because of 
the 80 bits precision for floats.
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