Hi,
I am trying to solve a second order ODE by calling a stepper for a number of fixed-size steps. I am getting an error about conversion to foreign type c-pointer.
I modeled my call to `apply-step' based on `apply-evolution'. Looking at the source files, that is likely not to work because `apply-evolution' uses c-pointers, and `apply-step' makes direct variable references. But I don't know how to deal with those - my C and CFFI knowledge are non-existent.
Anyway, here is a sample code that I hope someone can improve:
;;;; Example of a simple time-stepper (defun sin-ode (time y z) "Define ODE for a sinusoid
y''=-y
or as a system:
y'=z z'=-y
with initial conditions:
y0=0 z0=1 " (declare (ignore time)) (values z (- y)))
(defun sin-ode-jacobian (time y z) (declare (ignore time y z)) (values 0d0 0d0 0d0 1d0 -1d0 0d0)) #| (let ((time 0d0) (delta-t 0.1d0) (stepper-type +step-rk2+)) (let ((stepper (make-ode-stepper stepper-type 2 #'sin-ode #'sin-ode-jacobian)) (dep (make-marray 'double-float :dimensions 2)) (dydt-in (make-marray 'double-float :dimensions 2)) (dydt-out (make-marray 'double-float :dimensions 2)) (yerr (make-marray 'double-float :dimensions 2))) (setf (maref dep 0) 0d0 (maref dep 1) 1d0) (dotimes (i 10) (incf time delta-t) (apply-step stepper time dep delta-t yerr dydt-in dydt-out))))
|#
BTW, once this is working, I will submit it as a patch to the ode-examples.lisp file
Thanks,
Mirko