From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ffbox0-bg.mplayerhq.hu (ffbox0-bg.ffmpeg.org [79.124.17.100]) by master.gitmailbox.com (Postfix) with ESMTP id 3F20947290 for ; Tue, 2 Jan 2024 02:28:56 +0000 (UTC) Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id B175468CB0C; Tue, 2 Jan 2024 04:28:53 +0200 (EET) Received: from relay6-d.mail.gandi.net (relay6-d.mail.gandi.net [217.70.183.198]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id 6AC0D68BD5A for ; Tue, 2 Jan 2024 04:28:47 +0200 (EET) Received: by mail.gandi.net (Postfix) with ESMTPSA id 75E75C0004 for ; Tue, 2 Jan 2024 02:28:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=niedermayer.cc; s=gm1; t=1704162526; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc; bh=Qck0HJ/RNnqU7kaCJCTr08CeyVo8rhaLNsI7XCITGj4=; b=EC+MW9JMJytG4vxL9n7h0l1wqbu3QFxLDCoYEBO3Vrd9IXh99K8iH+4cS7N+qR2WYq8A2n eDSj88UrMfdMH13NxqnPJi1FOvpzCXJGAEbMX3P9XfXCXpiSJ3bSw4CNT3Tg/J6bo+ouFZ iRjX1gjRHVB48U4oJv8EDIF638s+PptawjYHl32QHANZ0a6Q59KKQFjyNEYrLGQCU2WnG9 nSGTbtkjiJuyDnaxP9RKIsPlZmnmmprGE6s/7tw+c6zefiNnKpJDIckVzRTaCC6NJvPSdA 8H1+hIQHsBfSQMzYWIR5oIUfzGWyTzOywYXkcfrpGyznkPwBe5/jRBlLLeVj1g== From: Michael Niedermayer To: FFmpeg development discussions and patches Date: Tue, 2 Jan 2024 03:28:45 +0100 Message-Id: <20240102022845.9916-1-michael@niedermayer.cc> X-Mailer: git-send-email 2.17.1 X-GND-Sasl: michael@niedermayer.cc Subject: [FFmpeg-devel] [PATCH] avutil/eval: Use integer for random() state X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" Archived-At: List-Archive: List-Post: 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 --- 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-request@ffmpeg.org with subject "unsubscribe".