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ift
NIFTy
Commits
57a67f20
Commit
57a67f20
authored
Mar 01, 2018
by
Martin Reinecke
Browse files
some tweaks
parent
068e855d
Pipeline
#25586
passed with stage
in 5 minutes and 38 seconds
Changes
1
Pipelines
1
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Inline
Side-by-side
nifty4/minimization/nonlinear_cg.py
View file @
57a67f20
...
...
@@ -22,12 +22,11 @@ from .line_search_strong_wolfe import LineSearchStrongWolfe
class
NonlinearCG
(
Minimizer
):
#RL FIXME: referenced equations in docstring seem broken for the version I found.
""" Nonlinear Conjugate Gradient scheme according to Polak-Ribiere.
Algorithm 5.4 from Nocedal & Wright.
Eq. (5.41a) has been replaced by eq. (5.49)
Eq. (5.41a) has been replaced by eq. (5.49)
Parameters
----------
controller : IterationController
...
...
@@ -41,11 +40,13 @@ class NonlinearCG(Minimizer):
2006, Springer-Verlag New York
"""
def
__init__
(
self
,
controller
,
line_searcher
=
LineSearchStrongWolfe
(
c2
=
0.1
),
beta_heuristics
=
'Polak-Ribiere'
):
valid_beta_heuristics
=
[
'Polak-Ribiere'
,
'Fletcher-Reeves'
,
'Polak-Ribiere'
]
def
__init__
(
self
,
controller
,
line_searcher
=
LineSearchStrongWolfe
(
c2
=
0.1
),
beta_heuristics
=
'Polak-Ribiere'
):
valid_beta_heuristics
=
[
'Polak-Ribiere'
,
'Fletcher-Reeves'
,
'Hestenes-Stiefel'
]
if
not
(
beta_heuristics
in
valid_beta_heuristics
):
raise
ValueError
(
"beta heuristics must be either 'Polak-Ribiere', "
\
+
"'Fletcher-Reeves', or 'Hestenes-Stiefel'"
)
raise
ValueError
(
"beta heuristics must be either 'Polak-Ribiere', "
"'Fletcher-Reeves', or 'Hestenes-Stiefel'"
)
self
.
_beta_heuristic
=
beta_heuristics
self
.
_controller
=
controller
self
.
_line_searcher
=
line_searcher
...
...
@@ -69,14 +70,16 @@ class NonlinearCG(Minimizer):
if
status
!=
controller
.
CONTINUE
:
return
energy
,
status
grad_new
=
energy
.
gradient
#print(grad_old.val, grad_new.val, p.val, energy.position.val)
if
self
.
_beta_heuristic
==
'Hestenes-Stiefel'
:
#Eq. (5.45) in Nocedal & Wright.
beta
=
max
(
0.0
,(
grad_new
.
vdot
(
grad_new
-
grad_old
)
/
(
grad_new
-
grad_old
).
vdot
(
p
)).
real
)
elif
self
.
_beta_heuristic
==
'Polak Ribiere'
:
#Eq. (5.43) in Nocedal & Wright. (with (5.44) additionally)
beta
=
max
(
0.0
,(
grad_new
.
vdot
(
grad_new
-
grad_old
)
/
(
grad_old
.
vdot
(
grad_old
))).
real
)
# Eq. (5.45) in Nocedal & Wright.
beta
=
max
(
0.0
,
(
grad_new
.
vdot
(
grad_new
-
grad_old
)
/
(
grad_new
-
grad_old
).
vdot
(
p
)).
real
)
elif
self
.
_beta_heuristic
==
'Polak-Ribiere'
:
# Eq. (5.43) in Nocedal & Wright. (with (5.44) additionally)
beta
=
max
(
0.0
,
(
grad_new
.
vdot
(
grad_new
-
grad_old
)
/
(
grad_old
.
vdot
(
grad_old
))).
real
)
else
:
#Eq. (5.40a) in Nocedal & Wright.
#
Eq. (5.40a) in Nocedal & Wright.
beta
=
(
grad_new
.
vdot
(
grad_new
)
/
(
grad_old
.
vdot
(
grad_old
))).
real
p
=
beta
*
p
-
grad_new
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