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Problem of lambdification I encountered, lambdified function that is difference of another function and a value is not equal to zero when we put as value the evaluation of other function at same point.
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from sympy import Symbol, pprint, log, lambdify | |
# setting symbols | |
g1 = Symbol("gamma1") | |
g2 = Symbol("gamma2") | |
g3 = Symbol("gamma3") | |
g4 = Symbol("gamma4") | |
rt = Symbol("rt") | |
# setting expressions | |
criteria = (g1 * log(g1, 2.0))/2.0 | |
criteria += (g2 * log(g2, 2.0))/2.0 | |
criteria += (g3 * log(g3, 2.0))/2.0 | |
criteria += (g4 * log(g4, 2.0))/2.0 | |
rooteq = criteria - rt | |
print "\ncriteria function: " | |
pprint(criteria) | |
print "\ncriteria function - rt: " | |
pprint(rooteq) | |
# lambdifying expressions to callable functions | |
tsymbols = [g1, g2, g3, g4, rt] | |
lambfun_criteria = lambdify(tsymbols, criteria) | |
lambfun_rooteq = lambdify(tsymbols, rooteq) | |
# example point x | |
x = [0.25006462253641376, 2.2501938662000542, 2.2501938662000542, 2.2501938662000542, 0.0] | |
# evaluating of criteria on x | |
rootval = lambfun_criteria(*x) | |
# setting rt to this evaluation | |
x[4] = rootval | |
print "\nactual evaluation of rooteq: " + str(lambfun_rooteq(*x)) | |
print "\nexpected evaluation of rooteq: " + str(- x[4] + lambfun_criteria(*x)) |
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from sympy import Symbol, pprint, log, lambdify | |
from mpmath import mp | |
mp.dps = 15 | |
# setting symbols | |
g1 = Symbol("gamma1") | |
g2 = Symbol("gamma2") | |
g3 = Symbol("gamma3") | |
g4 = Symbol("gamma4") | |
rt = Symbol("rt") | |
# setting expressions | |
criteria = (g1 * log(g1, 2.0))/2.0 | |
criteria += (g2 * log(g2, 2.0))/2.0 | |
criteria += (g3 * log(g3, 2.0))/2.0 | |
criteria += (g4 * log(g4, 2.0))/2.0 | |
rooteq = criteria - rt | |
print "\ncriteria function: " | |
pprint(criteria) | |
print "\ncriteria function - rt: " | |
pprint(rooteq) | |
# lambdifying expressions to callable functions | |
tsymbols = [g1, g2, g3, g4, rt] | |
lambfun_criteria = lambdify(tsymbols, criteria, "mpmath") | |
lambfun_rooteq = lambdify(tsymbols, rooteq, "mpmath") | |
# example point x | |
x = [0.25006462253641376, 2.2501938662000542, 2.2501938662000542, 2.2501938662000542, 0.0] | |
# evaluating of criteria on x | |
rootval = lambfun_criteria(*x) | |
# setting rt to this evaluation | |
x[4] = rootval | |
print "\nactual evaluation of rooteq: " + str(lambfun_rooteq(*x)) | |
print "\nexpected evaluation of rooteq: " + str(- x[4] + lambfun_criteria(*x)) |
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$ python lambdifytest.py | |
criteria function: | |
0.721347520444482⋅γ₁⋅log(γ₁) + 0.721347520444482⋅γ₂⋅log(γ₂) + 0.721347520444482⋅γ₃⋅log(γ | |
₃) + 0.721347520444482⋅γ₄⋅log(γ₄) | |
criteria function - rt: | |
0.721347520444482⋅γ₁⋅log(γ₁) + 0.721347520444482⋅γ₂⋅log(γ₂) + 0.721347520444482⋅γ₃⋅log(γ | |
₃) + 0.721347520444482⋅γ₄⋅log(γ₄) - rt | |
actual evaluation of rooteq: 4.4408920985e-16 | |
expected evaluation of rooteq: 0.0 |
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