To start with I cannot give a simple example using only sympy. I have only
been able to generate this failure using my modules. Below is code and
output showing as simple an example as I can generate with some
diagnostics. If you could suggest any other diagnostics I would appreciate
it.
The problem is that an expressing that should evaluation to zero does not
even thought by inspecting the output it should.
Demonstration code:
from sympy import symbols, sin, cos, simplify, srepr
from ga import Ga
from mv import Mv
from metric import linear_expand
from printer import Format
xy = symbols('x y',real=True)
x = symbols('x',real=True)
o2d = Ga('e_x e_y',g=[1,1],coords=xy)
o1d = Ga('e',g=[1],coords=[x])
grad2d = o2d.grad
grad1d = o1d.grad
A = o1d.mv('A','mv',f=True)
B = o1d.mv('B','mv',f=True)
print(r'\bs{A}=',A)
print(r'\bs{B}=',B)
print(r'\bs{AB}=',A*B)
diff = grad1d*(A*B) - (grad1d*A)*B -(grad1d.odot()*A)*B.odot()
print(diff)
E = linear_expand(diff.obj)
scalar =E[0][0]
vector =E[0][1]
print('scalar =',simplify(E[0][0]))
print('vector =',simplify(E[0][1]))
print('srepr =',srepr(scalar))
args = scalar.args
print('args =',args)
print(simplify(args[1]+args[3]))
print(type(args[1]))
print(type(args[3]))
print(args[1].args)
print(args[3].args)
Both scalar and vector should be zero. Note that if I use sympy 1.2 zero
is output. Output follows:
\bs{A}= A+A__x*e_x
\bs{B}= B+B__x*e_x
\bs{AB}= A*B + A__x*B__x+(A*B__x + A__x*B)*e_x
-A*Derivative(B__x, x) + A*Derivative(B__x, x) + A__x*Derivative(B, x) -
A__x*Derivative(B, x)+(A*Derivative(B, x) - A*Derivative(B, x) -
A__x*Derivative(B__x, x) + A__x*Derivative(B__x, x))*e_x
scalar = -A*Derivative(B__x, x) + A*Derivative(B__x, x) +
A__x*Derivative(B, x) - A__x*Derivative(B, x)
vector = A*Derivative(B, x) - A*Derivative(B, x) - A__x*Derivative(B__x, x)
+ A__x*Derivative(B__x, x)
srepr = Add(Mul(Integer(-1), Function('A')(Symbol('x', real=True)),
Derivative(Function('B__x')(Symbol('x', real=True)), Tuple(Symbol('x',
real=True), Integer(1)))), Mul(Function('A')(Symbol('x', real=True)),
Derivative(Function('B__x')(Symbol('x', real=True)), Tuple(Symbol('x',
real=True), Integer(1)))), Mul(Function('A__x')(Symbol('x', real=True)),
Derivative(Function('B')(Symbol('x', real=True)), Tuple(Symbol('x',
real=True), Integer(1)))), Mul(Integer(-1), Function('A__x')(Symbol('x',
real=True)), Derivative(Function('B')(Symbol('x', real=True)),
Tuple(Symbol('x', real=True), Integer(1)))))
args = (A__x(x)*Derivative(B(x), x), A(x)*Derivative(B__x(x), x),
-A__x(x)*Derivative(B(x), x), -A(x)*Derivative(B__x(x), x))
(-Derivative(B__x, x) + Derivative(B__x, x))*A
<class 'sympy.core.mul.Mul'>
<class 'sympy.core.mul.Mul'>
(Derivative(B__x(x), x), A(x))
(-1, Derivative(B__x(x), x), A(x))
--
You received this message because you are subscribed to the Google Groups
"sympy" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to sympy+unsubscr...@googlegroups.com.
To post to this group, send email to sympy@googlegroups.com.
Visit this group at https://groups.google.com/group/sympy.
To view this discussion on the web visit
https://groups.google.com/d/msgid/sympy/b61e03d3-9765-4687-98c4-3851791951df%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
