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[algs] Adjust solve_itp

This commit is contained in:
Behdad Esfahbod 2023-03-01 13:10:11 -07:00
parent aa10deaf42
commit d29d7b7a3d
2 changed files with 7 additions and 8 deletions
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11
src/hb-algs.hh
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@ -1344,7 +1344,10 @@ struct
HB_FUNCOBJ (hb_dec); HB_FUNCOBJ (hb_dec);
/* For documentation and implementation see: /* Adapted from kurbo implementation with extra parameters added,
* and finding for a particular range instead of 0.
*
* For documentation and implementation see:
* *
* [ITP method]: https://en.wikipedia.org/wiki/ITP_Method * [ITP method]: https://en.wikipedia.org/wiki/ITP_Method
* [An Enhancement of the Bisection Method Average Performance Preserving Minmax Optimality]: https://dl.acm.org/doi/10.1145/3423597 * [An Enhancement of the Bisection Method Average Performance Preserving Minmax Optimality]: https://dl.acm.org/doi/10.1145/3423597
@ -1355,12 +1358,12 @@ template <typename func_t>
double solve_itp (func_t f, double solve_itp (func_t f,
double a, double b, double a, double b,
double epsilon, double epsilon,
unsigned n0,
double k1,
double min_y, double max_y, double min_y, double max_y,
double &ya, double &yb, double &y) double &ya, double &yb, double &y)
{ {
unsigned n1_2 = (unsigned) (hb_max (ceil (log2 ((b - a) / epsilon)) - 1.0, 0.0)); unsigned n1_2 = (unsigned) (hb_max (ceil (log2 ((b - a) / epsilon)) - 1.0, 0.0));
const unsigned n0 = 1; // Hardwired
const double k1 = 0.2 / (b - a); // Hardwired.
unsigned nmax = n0 + n1_2; unsigned nmax = n0 + n1_2;
double scaled_epsilon = epsilon * double (1llu << nmax); double scaled_epsilon = epsilon * double (1llu << nmax);
double _2_epsilon = 2.0 * epsilon; double _2_epsilon = 2.0 * epsilon;
@ -1370,8 +1373,8 @@ double solve_itp (func_t f,
double r = scaled_epsilon - 0.5 * (b - a); double r = scaled_epsilon - 0.5 * (b - a);
double xf = (yb * a - ya * b) / (yb - ya); double xf = (yb * a - ya * b) / (yb - ya);
double sigma = x1_2 - xf; double sigma = x1_2 - xf;
// This has k2 = 2 hardwired for efficiency.
double b_a = b - a; double b_a = b - a;
// This has k2 = 2 hardwired for efficiency.
double b_a_k2 = b_a * b_a; double b_a_k2 = b_a * b_a;
double delta = k1 * b_a_k2; double delta = k1 * b_a_k2;
int sigma_sign = sigma >= 0 ? +1 : -1; int sigma_sign = sigma >= 0 ? +1 : -1;

4
src/hb-shape.cc
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@ -334,8 +334,6 @@ hb_shape_justify (hb_font_t *font,
} }
double epsilon = (b - a) / (1<<14); double epsilon = (b - a) / (1<<14);
const unsigned n0 = 1;
const double k1 = 0.2 / (b - a);
bool failed = false; bool failed = false;
auto f = [&] (double x) auto f = [&] (double x)
@ -361,8 +359,6 @@ hb_shape_justify (hb_font_t *font,
double itp = solve_itp (f, double itp = solve_itp (f,
a, b, a, b,
epsilon, epsilon,
n0,
k1,
min_target_width, max_target_width, min_target_width, max_target_width,
ya, yb, y); ya, yb, y);