source: branches/decorate/surrogate.py @ 855

#!/usr/bin/env python
#
# Author: Mike McKerns (mmckerns @caltech and @uqfoundation)
# Copyright (c) 2012-2016 California Institute of Technology.
# License: 3-clause BSD.  The full license text is available at:
#  - http://mmckerns.github.io/project/mystic/browser/mystic/LICENSE

from math import pi, cos, tanh

def ballistic_limit(h,a):
  """calculate ballistic limit

  Inputs:
    - h = thickness in (unknown) units
    - a = obliquity in (unknown) units

  Outputs:
    - v_bl = velocity (ballistic limit) in (unknown) units
"""
 #h = x[0] * 25.4 * 1e-3
 #a = x[1] * pi/180.0
  Ho = 0.5794
  s = 1.4004
  n = 0.4482
  return Ho * ( h / cos(a)**n )**s


from klepto.safe import inf_cache as memoized
#from klepto import inf_cache as memoized
from klepto.archives import cache, file_archive
from klepto.keymaps import picklemap, stringmap, hashmap
dumps = picklemap(flat=False)
encode = stringmap(flat=False)
hashed = hashmap(flat=False)
cache = cache(archive=file_archive('surrogate.pkl'))
#@memoized(keymap=dumps, tol=0, deep=True) # slower, but more robust
#@memoized(keymap=encode, tol=0, deep=True)
#@memoized(cache=cache, keymap=dumps)    # slower, but more robust
#@memoized(cache=cache, keymap=hashed)   # fails to cache (unhashable)
@memoized(cache=cache, keymap=encode)
def marc_surr(x):
  """calculate perforation area using a tanh-based model surrogate

  Inputs:
    - x = [thickness, obliquity, speed] in (unknown) units

  Outputs:
    - A = performation area in (unknown) units
"""
# h = thickness = [60,105]
# a = obliquity = [0,30]
# v = speed = [2.1,2.8]
  h = x[0] * 25.4 * 1e-3
  a = x[1] * pi/180.0
  v = x[2]

  K = 10.3963
  p = 0.4757
  u = 1.0275
  m = 0.4682
  Dp = 1.778

  # compare to ballistic limit
  v_bl = ballistic_limit(h,a)
  if v < v_bl:
    return 0

  return K * (h/Dp)**p * (cos(a))**u * (tanh((v/v_bl)-1))**m

# EOF