Module: Math

Defined in:
lib/regioned_calculation.rb

Class Method Summary collapse

Class Method Details

.find_root(a, b, precision = 0.01, allow_oob_roots = false, &blk) ⇒ Object

optimized version of find_root, performs 10000 roots’ calculations per sec on Core 2 Duo 2.67



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# File 'lib/regioned_calculation.rb', line 3

def self.find_root(a, b, precision=0.01, allow_oob_roots=false, &blk)
  fa, fb = yield(a).to_f, yield(b).to_f
  sa, sb = fa >= 0 ? 1 : -1, fb >= 0 ? 1 : -1
  while true do
    # puts "f(#{a},#{(a/precision).truncate})=#{fa}, f(#{b},#{(b/precision).truncate})=#{fb}"
    raise "Looking for roots out of bounds" if !allow_oob_roots && sa == sb
    return a if (a-b).abs < precision || fa.abs <= precision
    return b if fb.abs <= precision
    c = (a.to_f + b.to_f) / 2
    fc = yield(c)
    sc = fc >= 0 ? 1 : -1
    if sa != sc
      b, fb, sb = c, fc, sc
    else
      a, fa, sa = c, fc, sc
    end
  end
end