How to implement a parallelization?

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Consider a code of the kind tree exploration amassing fruits: when the procedure arrives to a new node of the tree, if it is a leaf a possible fruit is collected, else a computation is done to determine the children of the node. I would like to parallelize as follows: the children are allocated to all the available CPUs, each CPU has a queue and a given child is allocated to the CPU with the smallest queue.

It seems to be a generic way to parallelize such a tree exploration.

Question: How to implement such a parallelization?
In addition, how to use GPU (for HPC)?

The code has the following form:

cpdef function(list L1, list L2):
    cdef int i,n #...
    cdef list LL1,LL2 #...
    #...
    # core of the code
    #...
    n= #...
    for i in range(n):
        LL1= #...
        LL2= #...
        function(LL1,LL2)