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diffpy.pdfgui/src/diffpy/pdfgui/control/constraint.py at main · diffpy/diffpy.pdfgui · GitHub
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diffpy.pdfgui
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src
/
diffpy
/
pdfgui
/
control
/
constraint.py
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diffpy.pdfgui
/
src
/
diffpy
/
pdfgui
/
control
/
constraint.py
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#!/usr/bin/env python
##############################################################################
#
# PDFgui by DANSE Diffraction group
# Simon J. L. Billinge
# (c) 2006 trustees of the Michigan State University.
# All rights reserved.
#
# File coded by: Pavol Juhas
#
# See AUTHORS.txt for a list of people who contributed.
# See LICENSE.txt for license information.
#
##############################################################################
"""Class Constraint for storage of a single constraint equation
constraints will be stored in { variable : constraint } dictionary."""
import
math
import
re
from
diffpy
.
pdfgui
.
control
.
controlerrors
import
ControlSyntaxError
class
Constraint
:
"""Constraint --> storage and check of a single constraint equation.
Data members:
formula -- right-side of constraint equation (string). When
assigned it is checked for math correctness and updates
the parguess dictionary
parguess -- read-only dictionary of parameter indices and their
estimated initial values. Values are None if they
cannot be estimated.
Private members:
__lhs -- last value of constrained variable passed to guess()
"""
def
__init__
(
self
,
formula
,
value
=
None
):
"""Initialize the Constraint.
formula -- (string) right-side of constraint equation
value -- (optional) current value of the variable
__init__ raises ControlSyntaxError when formula is incorrect
"""
# initialize private members firsts
self
.
__lhs
=
None
self
.
parguess
=
{}
# initialize formula member avoid __setattr__
self
.
__dict__
[
"formula"
]
=
"None"
# formula should be assigned as a last one
self
.
formula
=
formula
if
value
is
not
None
:
self
.
guess
(
value
)
return
def
evalFormula
(
self
,
parvalues
):
"""Evaluate constraint formula.
parvalues -- dictionary of int parameter indices and float values.
returns formula result
"""
fncp
=
self
.
lambdaFormula
()
result
=
fncp
(
parvalues
)
return
result
def
lambdaFormula
(
self
):
"""Build lambda function from constraint formula. Lambda
function expects dictionary argument.
returns lambda function
"""
expr
=
re
.
sub
(
r"@(\d*)"
,
r"p[\1]"
,
self
.
formula
)
f
=
eval
(
"lambda p:"
+
expr
,
vars
(
math
))
return
f
def
guess
(
self
,
value
):
"""Guess the initial values of parameters contained in parguess.
value -- current value of the constrained variable
The keys of self.parguess are indices of parameters used in formula,
and the values are suggested parameter values (None if they cannot
be estimated).
returns a copy of self.parguess
"""
self
.
__lhs
=
float
(
value
)
for
k
in
self
.
parguess
:
self
.
parguess
[
k
]
=
None
# solve linear formulas of one variable
if
len
(
self
.
parguess
)
==
1
:
fncp
=
self
.
lambdaFormula
()
# check if fncp is linear with eps precision
try
:
eps
=
1.0e-8
lo
,
hi
=
1.0
-
eps
,
1.0
+
eps
(
k
,)
=
self
.
parguess
.
keys
()
y
=
[
fncp
({
k
:
0.25
}),
fncp
({
k
:
0.5
}),
fncp
({
k
:
0.75
})]
dy
=
[
y
[
1
]
-
y
[
0
],
y
[
2
]
-
y
[
1
]]
ady
=
[
abs
(
z
)
for
z
in
dy
]
if
lo
*
ady
[
0
]
<=
ady
[
1
]
<=
hi
*
ady
[
0
]
and
dy
[
0
]
!=
0.0
:
a
=
4
*
dy
[
0
]
b
=
y
[
1
]
-
0.5
*
a
self
.
parguess
[
k
]
=
(
value
-
b
)
/
a
except
(
ValueError
,
ZeroDivisionError
):
pass
return
dict
(
self
.
parguess
)
def
__setattr__
(
self
,
name
,
value
):
"""Check math and update parguess when formula is assigned."""
if
name
!=
"formula"
:
self
.
__dict__
[
name
]
=
value
return
# here we are assigning to formula
# first we need to check it it is valid
newformula
=
value
pars
=
re
.
findall
(
r"@\d+"
,
newformula
)
# require at least one parameter in the formula
if
len
(
pars
)
==
0
:
message
=
"No parameter in formula '%s'"
%
newformula
raise
ControlSyntaxError
(
message
)
try
:
# this raises ControlSyntaxError if newformula is invalid
# define fncx in math module namespace
fncx
=
eval
(
"lambda x:"
+
re
.
sub
(
r"@\d+"
,
"x"
,
newformula
),
vars
(
math
))
# check if fncx(0.25) is float
fncx
(
0.25
)
+
0.0
except
(
ValueError
,
SyntaxError
,
TypeError
,
NameError
):
message
=
"invalid constraint formula '%s'"
%
newformula
raise
ControlSyntaxError
(
message
)
# few more checks of the formula:
if
newformula
.
find
(
"**"
)
!=
-
1
:
emsg
=
(
"invalid constraint formula '{}', "
"operator '**' not supported."
).
format
(
newformula
)
raise
ControlSyntaxError
(
emsg
)
# checks checked
self
.
__dict__
[
"formula"
]
=
newformula
self
.
parguess
=
dict
.
fromkeys
([
int
(
p
[
1
:])
for
p
in
pars
])
if
self
.
__lhs
is
not
None
:
self
.
guess
(
self
.
__lhs
)
return
# End of class Constraint
# End of file
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