[FFmpeg-devel] [PATCH] avcodec/fft_template: use ff_thread_once on costable initialization

[Rostislav Pehlivanov]

On 5 July 2017 at 07:15, Muhammad Faiz <mfcc64 at gmail.com> wrote:

> Make it thread-safe and avoid redundant initialization.
>
> Signed-off-by: Muhammad Faiz <mfcc64 at gmail.com>
> ---
>  libavcodec/fft_template.c | 81 ++++++++++++++++++++++++++++++
> +++++++++++------
>  1 file changed, 71 insertions(+), 10 deletions(-)
>
> diff --git a/libavcodec/fft_template.c b/libavcodec/fft_template.c
> index 6477372..6c77854 100644
> --- a/libavcodec/fft_template.c
> +++ b/libavcodec/fft_template.c
> @@ -29,11 +29,19 @@
>  #include <stdlib.h>
>  #include <string.h>
>  #include "libavutil/mathematics.h"
> +#include "libavutil/thread.h"
>  #include "fft.h"
>  #include "fft-internal.h"
>
>  #if FFT_FIXED_32
>  #include "fft_table.h"
> +
> +static void av_cold fft_lut_init(void)
> +{
> +    int n = 0;
> +    ff_fft_lut_init(ff_fft_offsets_lut, 0, 1 << 17, &n);
> +}
> +
>  #else /* FFT_FIXED_32 */
>
>  /* cos(2*pi*x/n) for 0<=x<=n/4, followed by its reverse */
> @@ -52,6 +60,66 @@ COSTABLE(16384);
>  COSTABLE(32768);
>  COSTABLE(65536);
>  COSTABLE(131072);
> +
> +static av_cold void init_ff_cos_tabs(int index)
> +{
> +    int i;
> +    int m = 1<<index;
> +    double freq = 2*M_PI/m;
> +    FFTSample *tab = FFT_NAME(ff_cos_tabs)[index];
> +    for(i=0; i<=m/4; i++)
> +        tab[i] = FIX15(cos(i*freq));
> +    for(i=1; i<m/4; i++)
> +        tab[m/2-i] = tab[i];
> +}
> +
> +typedef struct CosTabsInitOnce {
> +    void (*func)(void);
> +    AVOnce control;
> +} CosTabsInitOnce;
> +
> +#define INIT_FF_COS_TABS_FUNC(index, size)          \
> +static av_cold void init_ff_cos_tabs_ ## size (void)\
> +{                                                   \
> +    init_ff_cos_tabs(index);                        \
> +}
> +
> +INIT_FF_COS_TABS_FUNC(4, 16)
> +INIT_FF_COS_TABS_FUNC(5, 32)
> +INIT_FF_COS_TABS_FUNC(6, 64)
> +INIT_FF_COS_TABS_FUNC(7, 128)
> +INIT_FF_COS_TABS_FUNC(8, 256)
> +INIT_FF_COS_TABS_FUNC(9, 512)
> +INIT_FF_COS_TABS_FUNC(10, 1024)
> +INIT_FF_COS_TABS_FUNC(11, 2048)
> +INIT_FF_COS_TABS_FUNC(12, 4096)
> +INIT_FF_COS_TABS_FUNC(13, 8192)
> +INIT_FF_COS_TABS_FUNC(14, 16384)
> +INIT_FF_COS_TABS_FUNC(15, 32768)
> +INIT_FF_COS_TABS_FUNC(16, 65536)
> +INIT_FF_COS_TABS_FUNC(17, 131072)
> +
> +static CosTabsInitOnce cos_tabs_init_once[] = {
> +    { NULL },
> +    { NULL },
> +    { NULL },
> +    { NULL },
> +    { init_ff_cos_tabs_16, AV_ONCE_INIT },
> +    { init_ff_cos_tabs_32, AV_ONCE_INIT },
> +    { init_ff_cos_tabs_64, AV_ONCE_INIT },
> +    { init_ff_cos_tabs_128, AV_ONCE_INIT },
> +    { init_ff_cos_tabs_256, AV_ONCE_INIT },
> +    { init_ff_cos_tabs_512, AV_ONCE_INIT },
> +    { init_ff_cos_tabs_1024, AV_ONCE_INIT },
> +    { init_ff_cos_tabs_2048, AV_ONCE_INIT },
> +    { init_ff_cos_tabs_4096, AV_ONCE_INIT },
> +    { init_ff_cos_tabs_8192, AV_ONCE_INIT },
> +    { init_ff_cos_tabs_16384, AV_ONCE_INIT },
> +    { init_ff_cos_tabs_32768, AV_ONCE_INIT },
> +    { init_ff_cos_tabs_65536, AV_ONCE_INIT },
> +    { init_ff_cos_tabs_131072, AV_ONCE_INIT },
> +};
> +
>  #endif
>  COSTABLE_CONST FFTSample * const FFT_NAME(ff_cos_tabs)[] = {
>      NULL, NULL, NULL, NULL,
> @@ -90,14 +158,7 @@ static int split_radix_permutation(int i, int n, int
> inverse)
>  av_cold void ff_init_ff_cos_tabs(int index)
>  {
>  #if (!CONFIG_HARDCODED_TABLES) && (!FFT_FIXED_32)
> -    int i;
> -    int m = 1<<index;
> -    double freq = 2*M_PI/m;
> -    FFTSample *tab = FFT_NAME(ff_cos_tabs)[index];
> -    for(i=0; i<=m/4; i++)
> -        tab[i] = FIX15(cos(i*freq));
> -    for(i=1; i<m/4; i++)
> -        tab[m/2-i] = tab[i];
> +    ff_thread_once(&cos_tabs_init_once[index].control,
> cos_tabs_init_once[index].func);
>  #endif
>  }
>
> @@ -176,8 +237,8 @@ av_cold int ff_fft_init(FFTContext *s, int nbits, int
> inverse)
>
>  #if FFT_FIXED_32
>      {
> -        int n=0;
> -        ff_fft_lut_init(ff_fft_offsets_lut, 0, 1 << 17, &n);
> +        static AVOnce control = AV_ONCE_INIT;
>

This needs to be a global variable.


> +        ff_thread_once(&control, fft_lut_init);
>      }
>  #else /* FFT_FIXED_32 */
>  #if FFT_FLOAT
> --
> 2.9.3
>
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