Limitations

FD does not support looping internally. All operations with loops, such as matrix vector multiplication, are unrolled into scalar operations. The corresponding executable functions generated by make_function have size proportional to the number of operations.

Expressions with ≈10⁵ scalar operations have reasonable symbolic preprocessing and compilation times. Beyond this size LLVM compilation time can become extremely long and eventually the executables become so large that their caching behavior is not good and performance declines.