rounding the 64bit integer state to double between each iteration causes a reduction in quality of the random number generator. For example its period drops from 2^64 to around 200 million
Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> --- libavutil/eval.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/libavutil/eval.c b/libavutil/eval.c index bad9e4ecb8d..89c61ba4bf5 100644 --- a/libavutil/eval.c +++ b/libavutil/eval.c @@ -55,6 +55,7 @@ typedef struct Parser { void *log_ctx; #define VARS 10 double *var; + uint64_t *var_uint64; } Parser; static const AVClass eval_class = { @@ -173,6 +174,7 @@ struct AVExpr { } a; struct AVExpr *param[3]; double *var; + uint64_t *var_uint64; }; static double etime(double v) @@ -230,9 +232,10 @@ static double eval_expr(Parser *p, AVExpr *e) } case e_random:{ int idx= av_clip(eval_expr(p, e->param[0]), 0, VARS-1); - uint64_t r= isnan(p->var[idx]) ? 0 : p->var[idx]; + uint64_t r= p->var_uint64[idx] ? p->var_uint64[idx] : (isnan(p->var[idx]) ? 0 : p->var[idx]); r= r*1664525+1013904223; p->var[idx]= r; + p->var_uint64[idx]= r; return e->value * (r * (1.0/UINT64_MAX)); } case e_while: { @@ -319,7 +322,11 @@ static double eval_expr(Parser *p, AVExpr *e) case e_div: return e->value * (d2 ? (d / d2) : d * INFINITY); case e_add: return e->value * (d + d2); case e_last:return e->value * d2; - case e_st : return e->value * (p->var[av_clip(d, 0, VARS-1)]= d2); + case e_st : { + int index = av_clip(d, 0, VARS-1); + p->var_uint64[index] = 0; + return e->value * (p->var[index]= d2); + } case e_hypot:return e->value * hypot(d, d2); case e_atan2:return e->value * atan2(d, d2); case e_bitand: return isnan(d) || isnan(d2) ? NAN : e->value * ((long int)d & (long int)d2); @@ -339,6 +346,7 @@ void av_expr_free(AVExpr *e) av_expr_free(e->param[1]); av_expr_free(e->param[2]); av_freep(&e->var); + av_freep(&e->var_uint64); av_freep(&e); } @@ -724,7 +732,8 @@ int av_expr_parse(AVExpr **expr, const char *s, goto end; } e->var= av_mallocz(sizeof(double) *VARS); - if (!e->var) { + e->var_uint64= av_mallocz(sizeof(uint64_t) *VARS); + if (!e->var || !e->var_uint64) { ret = AVERROR(ENOMEM); goto end; } @@ -766,6 +775,7 @@ double av_expr_eval(AVExpr *e, const double *const_values, void *opaque) { Parser p = { 0 }; p.var= e->var; + p.var_uint64= e->var_uint64; p.const_values = const_values; p.opaque = opaque; -- 2.17.1 _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".