[FFmpeg-devel] [PATCH 1/4] lavu/float_dsp: add double-precision scalar product

[Andreas Rheinhardt]

Rémi Denis-Courmont:
> The function pointer is appended to the structure for backward binary
> compatibility. Fortunately, this is allocated by libavutil, not by the
> user, so increasing the structure size is safe.
> ---
>  doc/APIchanges        |  3 +++
>  libavutil/float_dsp.c | 12 ++++++++++++
>  libavutil/float_dsp.h | 14 ++++++++++++++
>  libavutil/version.h   |  2 +-
>  4 files changed, 30 insertions(+), 1 deletion(-)
> 
> diff --git a/doc/APIchanges b/doc/APIchanges
> index 60f056b863..50c51c664f 100644
> --- a/doc/APIchanges
> +++ b/doc/APIchanges
> @@ -2,6 +2,9 @@ The last version increases of all libraries were on 2024-03-07
>  
>  API changes, most recent first:
>  
> +2024-05-29 - xxxxxxxxxx - lavu 59.21.100 - float_dsp.h
> +  Add AVFloatDSPContext.scalarproduct_double.

float_dsp.h is not a public header (the allocator is avpriv:
avpriv_float_dsp_alloc), so there must not be an APIchanges entry for this.

> +
>  2024-05-23 - xxxxxxxxxx - lavu 59.20.100 - channel_layout.h
>    Add av_channel_layout_ambisonic_order().
>  
> diff --git a/libavutil/float_dsp.c b/libavutil/float_dsp.c
> index e9fb023466..1c5bb05636 100644
> --- a/libavutil/float_dsp.c
> +++ b/libavutil/float_dsp.c
> @@ -132,6 +132,17 @@ float avpriv_scalarproduct_float_c(const float *v1, const float *v2, int len)
>      return p;
>  }
>  
> +static double ff_scalarproduct_double_c(const double *v1, const double *v2,

Don't use an ff_ prefix for a static function.

> +                                        size_t len)
> +{
> +    double p = 0.0;
> +
> +    for (size_t i = 0; i < len; i++)
> +        p += v1[i] * v2[i];
> +
> +    return p;
> +}
> +
>  av_cold AVFloatDSPContext *avpriv_float_dsp_alloc(int bit_exact)
>  {
>      AVFloatDSPContext *fdsp = av_mallocz(sizeof(AVFloatDSPContext));
> @@ -149,6 +160,7 @@ av_cold AVFloatDSPContext *avpriv_float_dsp_alloc(int bit_exact)
>      fdsp->vector_fmul_reverse = vector_fmul_reverse_c;
>      fdsp->butterflies_float = butterflies_float_c;
>      fdsp->scalarproduct_float = avpriv_scalarproduct_float_c;
> +    fdsp->scalarproduct_double = ff_scalarproduct_double_c;
>  
>  #if ARCH_AARCH64
>      ff_float_dsp_init_aarch64(fdsp);
> diff --git a/libavutil/float_dsp.h b/libavutil/float_dsp.h
> index 342a8715c5..b6b5b0a3b3 100644
> --- a/libavutil/float_dsp.h
> +++ b/libavutil/float_dsp.h
> @@ -19,6 +19,8 @@
>  #ifndef AVUTIL_FLOAT_DSP_H
>  #define AVUTIL_FLOAT_DSP_H
>  
> +#include <stddef.h>
> +
>  typedef struct AVFloatDSPContext {
>      /**
>       * Calculate the entry wise product of two vectors of floats and store the result in
> @@ -187,6 +189,18 @@ typedef struct AVFloatDSPContext {
>       */
>      void (*vector_dmul)(double *dst, const double *src0, const double *src1,
>                          int len);
> +
> +    /**
> +     * Calculate the scalar product of two vectors of doubles.
> +     *
> +     * @param v1  first vector
> +     * @param v2  second vector

Are these supposed to obey additional alignment beyond that imposed by
double? (Does your RISC-V implementation require it?)

> +     * @param len length of vectors
> +     *
> +     * @return inner product of the vectors
> +     */
> +    double (*scalarproduct_double)(const double *v1, const double *v2,
> +                                   size_t len);
>  } AVFloatDSPContext;
>  
>  /**
> diff --git a/libavutil/version.h b/libavutil/version.h
> index 9c7146c228..9d08d56884 100644
> --- a/libavutil/version.h
> +++ b/libavutil/version.h
> @@ -79,7 +79,7 @@
>   */
>  
>  #define LIBAVUTIL_VERSION_MAJOR  59
> -#define LIBAVUTIL_VERSION_MINOR  20
> +#define LIBAVUTIL_VERSION_MINOR  21
>  #define LIBAVUTIL_VERSION_MICRO 100
>  
>  #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \