Function ptr_diffs 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn ptr_diffs(
    q: *mut CompilerResult,
) -> *const f64

Returns a pointer to the differentials (count_diffs doubles).

The function calling execute reads the differentials from this area.

Note: whether the output is returned as observables or differentials is defined in the model.

Safety

it is the responsibility of the calling function to ensure
that q points to a valid CompilerResult.