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58 lines
1.8 KiB
Python
58 lines
1.8 KiB
Python
from sympy import quo
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from sympy import symbols, simplify, ccode
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from sympy.tensor.array import derive_by_array
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import sys
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def generate_cpp_tensor(expr, vars, order):
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derivatives = expr
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for _ in range(order):
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derivatives = derive_by_array(derivatives, vars)
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def flatten(tensor):
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if not hasattr(tensor, '__iter__') or isinstance(tensor, (str, bytes)):
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return [tensor]
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if hasattr(tensor, 'tolist'):
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tensor = tensor.tolist()
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flat_list = []
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for e in tensor:
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flat_list.extend(flatten(e))
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return flat_list
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flat_derivs = flatten(derivatives)
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def index_to_suffix(idx):
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return ''.join([str(vars[i]) for i in idx])
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def generate_indices(d, order):
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if order == 0:
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return [[]]
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else:
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smaller = generate_indices(d, order - 1)
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return [s + [i] for s in smaller for i in range(d)]
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all_indices = generate_indices(len(vars), order)
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var_names = []
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for idx in all_indices:
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suffix = ''.join(str(vars[i]) for i in idx)
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var_names.append(f"f_{suffix}")
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code_lines = []
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for var_name, expr in zip(var_names, flat_derivs):
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simplified = simplify(expr)
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c_expr = ccode(simplified)
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code_lines.append(f" T {var_name} = static_cast<T>({c_expr});")
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return_line = " return { " + ', '.join(var_names) + " };"
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return '\n'.join(code_lines) + '\n' + return_line
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if __name__ == "__main__":
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x, y, z = symbols('x y z')
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vars = [x, y]
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f = x/(y+x)*y/(x-y)
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order = int(sys.argv[1]) if len(sys.argv) > 1 else 2
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print(f"// Order-{order} derivative of f(x, y, z) = {f}")
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print("template<typename T>")
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print("std::vector<T> gf_a(T x, T y) {")
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print(generate_cpp_tensor(f, vars, order))
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print("}")
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