;
; iron_optimize.hsp — 最適化 (勾配降下法 / 黄金分割法)
;
#ifndef __iron_optimize_hsp__
#define __iron_optimize_hsp__
#module iron_optimize

; Golden section search: find minimum of f(x) in [a, b]
; f is evaluated as x*x - 4*x + 4 (example: minimum at x=2)
#defcfunc optimize_golden double a, double b, int max_iter, \
	local gr, local c, local d, local fc, local fd
	gr = 0.6180339887  ; (sqrt(5)-1)/2
	repeat max_iter
		c = b - gr * (b - a)
		d = a + gr * (b - a)
		fc = c*c - 4.0*c + 4.0
		fd = d*d - 4.0*d + 4.0
		if fc < fd { b = d } else { a = c }
	loop
	return (a + b) / 2.0

#global
#endif