[FFmpeg-cvslog] eval: Add taylor series evaluation support.
Michael Niedermayer
git at videolan.org
Wed Feb 22 23:19:54 CET 2012
ffmpeg | branch: master | Michael Niedermayer <michaelni at gmx.at> | Tue Feb 21 20:47:18 2012 +0100| [43b1943a55b4b9de962761db38d5ecc3c8eef45a] | committer: Michael Niedermayer
eval: Add taylor series evaluation support.
Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=43b1943a55b4b9de962761db38d5ecc3c8eef45a
---
doc/eval.texi | 7 +++++++
libavutil/eval.c | 22 +++++++++++++++++++++-
tests/ref/fate/eval | 6 ++++++
3 files changed, 34 insertions(+), 1 deletions(-)
diff --git a/doc/eval.texi b/doc/eval.texi
index 92fdc6d..b481bfe 100644
--- a/doc/eval.texi
+++ b/doc/eval.texi
@@ -106,6 +106,13 @@ the evaluation of @var{y}, return 0 otherwise.
@item ifnot(x, y)
Evaluate @var{x}, and if the result is zero return the result of the
evaluation of @var{y}, return 0 otherwise.
+
+ at item taylor(expr, x)
+Evaluate a taylor series at x.
+expr represents the LD(0)-th derivates of f(x) at 0.
+note, when you have the derivatives at y instead of 0
+taylor(expr, x-y) can be used
+When the series does not converge the results are undefined.
@end table
The following constants are available:
diff --git a/libavutil/eval.c b/libavutil/eval.c
index 1a18bf9..fda0997 100644
--- a/libavutil/eval.c
+++ b/libavutil/eval.c
@@ -134,7 +134,7 @@ struct AVExpr {
e_squish, e_gauss, e_ld, e_isnan,
e_mod, e_max, e_min, e_eq, e_gt, e_gte,
e_pow, e_mul, e_div, e_add,
- e_last, e_st, e_while, e_floor, e_ceil, e_trunc,
+ e_last, e_st, e_while, e_taylor, e_floor, e_ceil, e_trunc,
e_sqrt, e_not, e_random, e_hypot, e_gcd,
e_if, e_ifnot,
} type;
@@ -181,6 +181,23 @@ static double eval_expr(Parser *p, AVExpr *e)
d=eval_expr(p, e->param[1]);
return d;
}
+ case e_taylor: {
+ double t = 1, d = 0, v;
+ double x = eval_expr(p, e->param[1]);
+ int i;
+ double var0 = p->var[0];
+ for(i=0; i<1000; i++) {
+ double ld = d;
+ p->var[0] = i;
+ v = eval_expr(p, e->param[0]);
+ d += t*v;
+ if(ld==d && v)
+ break;
+ t *= x / (i+1);
+ }
+ p->var[0] = var0;
+ return d;
+ }
default: {
double d = eval_expr(p, e->param[0]);
double d2 = eval_expr(p, e->param[1]);
@@ -318,6 +335,7 @@ static int parse_primary(AVExpr **e, Parser *p)
else if (strmatch(next, "isnan" )) d->type = e_isnan;
else if (strmatch(next, "st" )) d->type = e_st;
else if (strmatch(next, "while" )) d->type = e_while;
+ else if (strmatch(next, "taylor")) d->type = e_taylor;
else if (strmatch(next, "floor" )) d->type = e_floor;
else if (strmatch(next, "ceil" )) d->type = e_ceil;
else if (strmatch(next, "trunc" )) d->type = e_trunc;
@@ -698,6 +716,8 @@ int main(int argc, char **argv)
"if(1, 2)",
"ifnot(0, 23)",
"ifnot(1, NaN) + if(0, 1)",
+ "taylor(1, 1)",
+ "taylor(eq(mod(ld(0),4),1)-eq(mod(ld(0),4),3), PI/2)",
NULL
};
diff --git a/tests/ref/fate/eval b/tests/ref/fate/eval
index 09e310f..e5e796c 100644
--- a/tests/ref/fate/eval
+++ b/tests/ref/fate/eval
@@ -169,5 +169,11 @@ Evaluating 'ifnot(0, 23)'
Evaluating 'ifnot(1, NaN) + if(0, 1)'
'ifnot(1, NaN) + if(0, 1)' -> 0.000000
+Evaluating 'taylor(1, 1)'
+'taylor(1, 1)' -> 2.718282
+
+Evaluating 'taylor(eq(mod(ld(0),4),1)-eq(mod(ld(0),4),3), PI/2)'
+'taylor(eq(mod(ld(0),4),1)-eq(mod(ld(0),4),3), PI/2)' -> 1.000000
+
12.700000 == 12.7
0.931323 == 0.931322575
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