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

[Michael Niedermayer <michael@niedermayer.cc>]

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On Tue, Jan 23, 2024 at 04:17:22PM -0300, James Almer wrote:
> 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.


with float.h

float_near_abs_eps_array

Test checkasm-aacencdsp failed. Look at tests/data/fate/checkasm-aacencdsp.err for details.
checkasm: using random seed 4097080137
test failed comparing 5.68635 with 5.68635 (abs diff=4.76837e-07 with EPS=1.19209e-07)
SSE:
   abs_pow34_sse (aacencdsp.c:56)
 - aacencdsp.abs_pow34 [FAILED]
checkasm: 1 of 1 tests have failed
threads=1
src/tests/Makefile:317: recipe for target 'fate-checkasm-aacencdsp' failed
make: *** [fate-checkasm-aacencdsp] Error 1

if (!float_near_abs_eps_array(out, out2, FLT_EPSILON*10, BUF_SIZE))
works but feels wrong

this works too (only tested 100x on only x86-32 yet)
if (!float_near_ulp_array(out, out2, 1, BUF_SIZE))

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I am the wisest man alive, for I know one thing, and that is that I know
nothing. -- Socrates

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