Thank you so much for your detailed reply and patient help! I’m so happy to find out that sunode can give a solution!
One challenge I’m currently facing is that: instead of the 3*3 matrix A and the vector y with length 3, in reality, my matrix is actually 85 * 85 and len(y) = 85. Then I find that it takes quite a long time to run your code above (about 10hours on my laptop). I’m wondering what has caused this and if there’s any way to speed up? Thank you so much!