cython map with int k, with value a struct

问题

I discovered cython yesterday and a couple of cdef for my numpy structures improved execution time by 50% making my 24 hr run just 12 hours. Incredible!

I have a python dictionary with an integer key, containing a dictionary with 2 fixed keys each containing a float. This structure is accessed a crazy number of times. Hopping that cython can speed this up as well.

cython documentation talks about c++ map and makes reference to map.pxd. I have zero experience in c++, but it appears cython will be able to speed up my code, I just need a little help.

At the start of my loop:

# This dictionary will hold at maximum 100*1000
#     key is an int between 0 and 200000,  
#        index_0_start is defined above as "cdef int index_0_start"
#     value is an object/struct containing 2 floats
t_minus_1 = {index_0_start: {"pb": 1.0, "pnb": 0.0}}

Many checks if key exists:

    # s is an integer, cdef int s
    if not s in time_t:
        time_t[s] = {"pb": 0, "pnb": 0}

Many accesses for calculations

# s is an integer, mv_ctc is a memory view, twk is a float
time_t[s]["pb"] = time_t[s]["pb"] + mv_ctc[t,blank_index] * twk * ( t_minus_1[s]["pb"] + t_minus_1[s]["pnb"] )

Currently sorting the above dictionaries and selecting the best k entries with the python code. 100 times less than above, but still a crazy number of times. Hoping c++/cython can simplify this with a sortable map plus delete entries bellow k.

# calculate k most probable hypothesis  
prob_hythotesis = []
for s in time_t:
    p = ( time_t[s]["pb"] + time_t[s]["pnb"] )*length_in_graph[s]**beta
    prob_hythotesis.append((s, p))
prob_hythotesis.sort(key = lambda x: x[1], reverse=True) 

# shift state to time t-1
t_minus_1 = {}
for sp in prob_hythotesis[0: min(k+1, len(prob_hythotesis))]:
    s = sp[0]
    t_minus_1[s]=time_t[s]

The closest stackover response is 5 years old and different enough that my zero c++ experience is leaving me lost. Any help is appreciated.

来源：https://stackoverflow.com/questions/60472223/cython-map-with-int-k-with-value-a-struct

标签

python-3.x

dictionary

cython