Pythonコールバック関数のargtypeを設定します。

Question

私はPythonで非常にグリーンです。

全体的な問題は、PythonからCルーチンを呼び出すことです。私は一緒にいくつかの関連する質問/答えを一緒にklugingでかなり近づくことができますが、私は事がきちんと一緒に来るように見えることはできません。 2つの側面があります：最初にポインタでCルーチンを呼び出し、2つ目はコールバック関数を使用することです。

背景 Rubner Cで書かれた地球ムーバーの距離（EMD）ルーチン[EMD C code location]彼はまたEMDルーチンを呼び出す2つの例示のCプログラムを提供するを提供します。私は、例えばEMDルーチンを呼び出すexample2.cの代わりにPythonルーチンを開発しようとしています。 （はい、私はEMDのOpenCVの実装に精通しているよ。）ここでは便宜上

が私のpythonから呼び出したいemd.cコードのヘッダファイルです：最後に

/* DEFINITIONS */ 
#define MAX_SIG_SIZE 100 
#define MAX_ITERATIONS 500 
#define INFINITY  1e20 
#define EPSILON  1e-6 

/*****************************************************************************/ 
/* feature_t SHOULD BE MODIFIED BY THE USER TO REFLECT THE FEATURE TYPE  */ 
typedef int feature_t; 
/* typedef struct { int X,Y,Z; } feature_t;*/ 
/*typedef struct { int X; } feature_t; */ 
/*****************************************************************************/ 

typedef struct 
{ 
    int n;    /* Number of features in the signature */ 
    feature_t *Features; /* Pointer to the features vector */ 
    float *Weights;  /* Pointer to the weights of the features */ 
} signature_t; 

typedef struct 
{ 
    int from;    /* Feature number in signature 1 */ 
    int to;    /* Feature number in signature 2 */ 
    float amount;   /* Amount of flow from "from" to "to" */ 
} flow_t; 

float emd(signature_t *Signature1, signature_t *Signature2, 
     float (*func)(feature_t *, feature_t *), 
     flow_t *Flow, int *FlowSize); 

#endif 

を、ここに私はこれまで一緒にklugedしているpythonコードです。構造が正しく設定されているとは思うが（確かではない） （これは、Rubnerのemd.cコード内の可能な機能構造の簡略化されたバージョンであることに注意してください。私は最終的にすべての機能を有効にしたいと思いますが、今は簡単に始めています。呼び出し関数のargtypeのどこかにあります。私はいくつかのバリエーションを試しましたが、ウェブ上で利用できる例はかなりスリムで、私は壁に当たっています。

import ctypes 

MAX_FEATURE_SIZE = 30 
ARRAYFE = ctypes.c_int*MAX_FEATURE_SIZE 
ARRAYWE= ctypes.c_float*MAX_FEATURE_SIZE 
ARRAYFL = ctypes.c_float*(2*MAX_FEATURE_SIZE-1) 
flowSize = ctypes.c_int 

emdlib = ctypes.CDLL('emdlib.dylib') 
ctypes.CMPFUNC = ctypes.CFUNCTYPE(ctypes.c_float, ctypes.POINTER(ctypes.c_int), ctypes.POINTER(ctypes.c_int)) 

def py_dist_func(f1,f2): 
    print "dist: ", f1, f2 
    return(abs(f1-f2)) 

dist = ctypes.CMPFUNC(py_dist_func) 

n = ctypes.c_int 
flowSize = ctypes.c_int 

class flow_t(ctypes.Structure): 
    _fields_ = [("from", ctypes.c_int), 
       ("to", ctypes.c_int), 
       ("amount", ctypes.c_float)] 

class signature_t(ctypes.Structure): 
    _fields_ = [("N", n),("feature", ARRAYFE), 
       ("weight", ARRAYWE)] 

# emdlib.emd.argtypes = [ctypes.POINTER(signature_t), ctypes.POINTER(signature_t), ctypes.POINTER(ctypes.c_float), ctypes.POINTER(flow_t), ctypes.POINTER(ctypes.c_int)] 

# emdlib.emd.argtypes = [ctypes.POINTER(signature_t), ctypes.POINTER(signature_t), ctypes.CMPFUNC(py_dist_func), ctypes.POINTER(flow_t), ctypes.POINTER(ctypes.c_int)] 


emdlib.emd.argtypes = [ctypes.POINTER(signature_t), ctypes.POINTER(signature_t), ctypes.c_float, ctypes.POINTER(flow_t), ctypes.POINTER(ctypes.c_int)] 

# emd.restype = ctypes.c_float 
emdlib.emd.restype = flow_t 

signature1=signature_t() 
signature2=signature_t() 
feature1 = ARRAYFE 
feature2 = ARRAYFE 
weight1 =ARRAYWE 
weight2 = ARRAYWE 

feature1 = [0,1,2,3] 
feature2 = [0,3] 
weight1 = [1,1,1,1] 
weight2 = [1,1] 

#signature1= [4,feature1, weight1] 
#signature2 = [2, feature2, weight2] 
# sample: arr = (ctypes.c_int * len(pyarr))(*pyarr) 

signature1.N = len(feature1) 
signature1.feature = (ctypes.c_int * MAX_FEATURE_SIZE)(*feature1) 
signature2.feature = (ctypes.c_int * MAX_FEATURE_SIZE)(*feature2) 
signature1.weight = (ctypes.c_float * MAX_FEATURE_SIZE)(*weight1) 
signature2.weight = (ctypes.c_float * MAX_FEATURE_SIZE)(*weight2) 


e = emdlib.emd(ctypes.byref(signature1), ctypes.byref(signature2), dist, ctypes.POINTER(flow_t), flowSize) 

print "EMD= ", e 
print "flowSize", flowSize 

私が間違っていた箇所についてのご意見をいただければ幸いです。

私が実行すると確信している2番目の問題は、ポインタを返すargtypesです。ここの提案も同様に評価されるだろう。

ありがとうございます。

--------------様々な難解な方法で貴重なコメントで更新（作業）CODE

import ctypes 
import math 
import itertools 

MAX_FEATURE_SIZE = 25 

FEATURE_t = ctypes.c_int 
FEATURE_ptr = ctypes.POINTER(FEATURE_t) 

WEIGHT_t = ctypes.c_float 
WEIGHT_ptr = ctypes.POINTER(WEIGHT_t) 

COUNT_t = ctypes.c_int 
COUNT_ptr = ctypes.POINTER(COUNT_t) 

class FLOW_t(ctypes.Structure): 
    _fields_ = [("frm", ctypes.c_int), 
       ("to", ctypes.c_int), 
       ("amount", ctypes.c_float)] 

# Note that ctypes.POINTER is compatible with a ctypes array declared 
# as TYPE * array_len. This is equivalent to the way we can say 'char 
# *foo = "ABCDEF"' in C. 
class SIGNATURE_t(ctypes.Structure): 
    _fields_ = [("N", COUNT_t), 
       ("feature", FEATURE_ptr), 
       ("weight", WEIGHT_ptr)] 

FLOW_ARRAY_t = FLOW_t * (2*MAX_FEATURE_SIZE - 1) 
CMPFUNC_t = ctypes.CFUNCTYPE(ctypes.c_float, FEATURE_ptr, FEATURE_ptr) 

SIGNATURE_ptr = ctypes.POINTER(SIGNATURE_t) 
FLOW_ptr = ctypes.POINTER(FLOW_t) 

# Convenience function - keeps us from having to remember all the types and parameters later on 

def make_signature(features, weights): 
    sig = SIGNATURE_t() 
    sig.N = len(features) 
    sig.feature = (len(features) * FEATURE_t)(*features) 
    sig.weight = (len(weights) * WEIGHT_t)(*weights) 
    return sig 

# We want to pass into C a custom distance function from Python 
def py_dist_func(f1,f2): 
# print "f1, f2: %d, %d" % (f1[0], f2[0]) 
    d= distance(f1[0],f2[0]) 
    return d 

# set this up as a holder for distance function between any two n-D points 
def distance(p0,p1): 
    return(math.fabs(p0-p1)) 

dist_callback = CMPFUNC_t(py_dist_func) 

#print "Importing emdlib" 
emdlib = ctypes.CDLL('emdlib.dylib') 
#print "Setting argtypes" 
emdlib.emd.argtypes = [ SIGNATURE_ptr, 
         SIGNATURE_ptr, 
         CMPFUNC_t, 
         FLOW_ptr, 
         COUNT_ptr ] 
#print "Setting restype" 
emdlib.emd.restype = ctypes.c_float 

feature1 = [0, 1,2,3,4,5,6,7,8] 
feature2 = [0, 1,2,3,4,5,6,7,8] 
weight1 = [0.275,0.296,0.002,0.131,0.208,0.048,0.058,0.098,0.455] 
weight2 = [0.285,0.421,0.028,0.021,0.240,0.166,0.023,0.054,0.469] 

#print "Creating signatures" 
signature1 = make_signature(feature1, weight1) 
signature2 = make_signature(feature2, weight2) 

flow_array = FLOW_ARRAY_t() 
flow_size = COUNT_t() 

#print "Calling EMD" 
e = emdlib.emd(ctypes.byref(signature1), 
       ctypes.byref(signature2), 
       dist_callback, 
       flow_array, 
       ctypes.byref(flow_size)) 

print "EMD= ", e 
print "Number of FlowS", flow_size.value 

print "Flow" 
print "from to amount" 
totalFlow=0.0 
for i in range(0,flow_size.value): 
# print "Flow from %d to %d amount :%f" %(flow_array[i].frm, flow_array[i].to, flow_array[i].amount) 
    print " %d %d %f" %(flow_array[i].frm, flow_array[i].to, flow_array[i].amount) 
    totalFlow=totalFlow+flow_array[i].amount 

# 
# now adjust EMD to account for different signature masses and make it a metric 
alpha=1.0 

mass1=sum(weight1) 
mass2=sum(weight2) 

fList=[feature1,feature2] 

max_distance= 0.0 
for p0, p1 in list(itertools.product(*fList)): 
# print p0,p1, distance(p0,p1), max_distance 
    max_distance = max(max_distance, distance(p0, p1)) 

print "\nMax distance= %f" % max_distance 
print "Total Source = %f" % mass1 
print "Total Demand = %f" % mass2 
print "Total Flow= %f\n " % totalFlow 
print "Alpha = %f\n" %alpha 

# emdHat = e*totalFlow+math.sqrt((mass1-mass2)*(mass1-mass2))*alpha*max_distance 
emdHat = e*totalFlow+math.fabs((mass1-mass2))*alpha*max_distance 
print "Corrected Earth Movers Distance \n" 
print "emdHat = %f\n" % emdHat; 

Answer 1

は、私は最終的に動作するコードの断片を得ました。私がコメントで述べたように、私はエチケットが何であるか分かりませんが、コードの最後の部分を投稿すると便利だと思っていたのと同様の質問が出ました。それはきれいではありません。あなたがそれをきれいにするのに十分役に立つと思えば、私はより洗練された実装へのリンクを感謝します。