在C++中嵌入Python:在Python脚本中导入模块在一个函数调用过程中有效，但在另一个调用过程中无效

我正在编写一个程序，该程序使用C++作为数据管理后端，可以调用用户创建的python脚本来执行各种任务。我遇到了一个问题，虽然与导入python脚本中的模块有关。我将C++中的值传递给python，并从sklearn中对这些值执行高斯过程回归，然后简单地将优化的模型值或GPR不确定性返回给C++。我将这两种情况(模型优化和模型验证)作为python脚本中的两个独立函数，因为它们将从C++的不同位置调用。

当我运行第一个函数(模型优化)时，一切都很好，我得到了优化的超参数，可以毫无意外地返回C++。然而，在第二个函数调用期间，脚本失败，因为它无法从sklearn导入GPR模块(与上一个函数成功导入的模块相同)。我不太熟悉将python嵌入C++，所以很可能我只是遗漏了一些东西，或者没有完全理解规则。从C++端提供一个可以自己运行的代码是不可能的，所以我会尽我所能提供尽可能多的嵌入代码。下面的python脚本完整显示。如果您需要更多信息，请告诉我，我很乐意提供。谢谢您的帮助。

C++：主

//other stuff
Py_Initialize();
//do more other stuff (embedding happens here)
Py_Finalize();
//do even more other stuff

C++：模型优化

PyRun_SimpleString("import sys");
PyRun_SimpleString("sys.path.append(".")");
pName = PyString_FromString(file.c_str());
pModule = PyImport_Import(pName);
Py_DECREF(pName);
if (pModule != NULL) {
pFunc = PyObject_GetAttrString(pModule, function.c_str());
pArgs = PyTuple_New(size);
PyTuple_SetItem(pArgs, 0, PyLong_FromLong(gp->getInnerFPSize()));
PyTuple_SetItem(pArgs, 1, PyLong_FromLong(ntrain));
k = 2;
for(i = 0; i < trainingFP[modelNumber].size(); i++){
for(j = 0; j < trainingFP[modelNumber][i].size(); j++){
PyTuple_SetItem(pArgs, k, 
PyFloat_FromDouble(trainingFP[modelNumber][i][j]));
k++;
}           
}
for(i = 0; i < trainingForces[modelNumber].size(); i++){
PyTuple_SetItem(pArgs, k, 
PyFloat_FromDouble(trainingForces[modelNumber][i]));
k++;
}
Py_INCREF(pValue);
pValue = PyObject_CallObject(pFunc, pArgs);
Py_DECREF(pArgs);
}else {
PyErr_Print();
fprintf(stderr, "Failed to load "%s"n", function.c_str());
return 1;
}
Py_XDECREF(pFunc);
Py_DECREF(pModule);
optimalSigma = PyFloat_AsDouble(PyList_GetItem(pValue, 1));
optimalSigmaN = PyFloat_AsDouble(PyList_GetItem(pValue, 0));
optimalSigmaF = PyFloat_AsDouble(PyList_GetItem(pValue, 2));
Py_DECREF(pValue);

C++：模型验证

PyRun_SimpleString("import sys");
PyRun_SimpleString("sys.path.append(".")");
pName = PyString_FromString(file.c_str());
pModule = PyImport_Import(pName);
Py_DECREF(pName);
if (pModule != NULL) {
pFunc = PyObject_GetAttrString(pModule, function.c_str());
pArgs = PyTuple_New(size);
PyTuple_SetItem(pArgs, 0, PyFloat_FromDouble(testFP[0].size()));
PyTuple_SetItem(pArgs, 1, PyFloat_FromDouble(testFP.size()));
PyTuple_SetItem(pArgs, 2, PyFloat_FromDouble(trainingFP.size()));
PyTuple_SetItem(pArgs, 3, PyFloat_FromDouble(sigma));
PyTuple_SetItem(pArgs, 4, PyFloat_FromDouble(sigmaN));
PyTuple_SetItem(pArgs, 5, PyFloat_FromDouble(sigmaF));
k = 6;
for(i = 0; i < testFP.size(); i++){
for(j = 0; j < testFP[i].size(); j++){
PyTuple_SetItem(pArgs, k, PyFloat_FromDouble(testFP[i][j]));
k++;
}           
}
for(i = 0; i < trainingFP.size(); i++){
for(j = 0; j < trainingFP[i].size(); j++){
PyTuple_SetItem(pArgs, k, PyFloat_FromDouble(trainingFP[i][j]));
k++;
}           
}
for(i = 0; i < trainingFP.size(); i++){
PyTuple_SetItem(pArgs, k, PyFloat_FromDouble(trainingForces[i]));
k++;
}
Py_INCREF(pValue);
pValue = PyObject_CallObject(pFunc, pArgs);
Py_DECREF(pArgs);
}else {
PyErr_Print();
fprintf(stderr, "Failed to load "%s"n", function.c_str());
}
Py_XDECREF(pFunc);
Py_DECREF(pModule);
for(i = 0; i < testFP.size(); i++)
prediction[i] = PyFloat_AsDouble(PyList_GetItem(pValue, i));
Py_DECREF(pValue);

Python

def GPR(*X):
from sklearn.gaussian_process import GaussianProcessRegressor
from sklearn.gaussian_process.kernels import RBF, WhiteKernel
import re
#initialize local variables
counter = 0
sigma_l_initial = 1
sigma_n_initial = 1
sigma_f_initial = 2
innerFPSize = int(X[0])
ntrain = int(X[1])
optimized_hyperparameters = []
forces = []
fp = [] 
sigma_l_bounds = [.01,100]
sigma_n_bounds = [.001,.1]
fp.append([])
#pass values from c++ conversion tuple to local lists
for x in X:
if counter > 1 and counter < 2 + innerFPSize * ntrain:
fp[len(fp) - 1].append(x)
elif counter >= 2 + innerFPSize * ntrain:
forces.append(x)
counter += 1
if len(fp[len(fp) -1]) == innerFPSize:
if len(fp) < ntrain:
fp.append([])
#GPR routine
krbf = sigma_f_initial*RBF(length_scale=sigma_l_initial,length_scale_bounds=(sigma_l_bounds[0],sigma_l_bounds[1]))
noise_kernel = WhiteKernel(noise_level=sigma_n_initial,noise_level_bounds=(sigma_n_bounds[0],sigma_n_bounds[1]))
gp = GaussianProcessRegressor(kernel=krbf + noise_kernel,normalize_y=True,n_restarts_optimizer=25)
gp.fit(fp, forces)
#get optimized hyperparameters
rr = re.findall("[-+]?[.]?[d]+(?:,ddd)*[.]?d*(?:[eE][-+]?d+)?", str(gp.kernel_))
optimized_hyperparameters.append(float(rr[-1]))
optimized_hyperparameters.append(float(rr[-2]))
optimized_hyperparameters.append(float(rr[0]))
return optimized_hyperparameters


def GPR_unc(*X):
try:
from sklearn.gaussian_process import GaussianProcessRegressor
from sklearn.gaussian_process.kernels import RBF, WhiteKernel
except:
print 'THIS REFUSES TO WORK'
#initialize variables
uncertainty = []
testFP = []
trainingFP = []
trainingForces = []
innerFPSize = int(X[0])
testSize = int(X[1])
ntrain = int(X[2])
sigma = float(X[3])
sigma_n = float(X[4])
sigma_f = float(X[5])
counter = 0
setTrainFP = setTrainForces = False
setTestFP = True
testFP.append([])
trainingFP.append([])
#parse data from C++ arrays
for x in X:
try:
if counter > 5 and setTestFP == True:
testFP[len(testFP) - 1].append(x)
elif setTrainFP == True:
trainingFP[len(trainingFP) - 1].append(x)
elif setTrainForces == True:
trainingForces.append(x)
if counter > 5 and setTestFP == True:
if len(testFP[len(testFP) -1]) == innerFPSize:
if len(testFP) + 1 <= testSize:
testFP.append([])
else:
setTestFP = False
setTrainFP = True                                   
elif setTrainFP == True:
if len(trainingFP[len(trainingFP) -1]) == innerFPSize:
if(len(trainingFP)) + 1 <= ntrain:
trainingFP.append([])
else:
setTrainFP = False
setTrainForces = True
counter += 1
except:
print 'ERROR'
#perform static "optimization" of gpr kernel to get gpr object
krbf = sigma_f**2*RBF(length_scale=sigma,length_scale_bounds=(sigma,sigma))
noise_kernel = WhiteKernel(noise_level=sigma_n,noise_level_bounds=(sigma_n,sigma_n))
gp = GaussianProcessRegressor(kernel=krbf + noise_kernel,normalize_y=True, optimizer=None)
gp.fit(trainingFP, trainingForces)
#get uncertanties on test set
val,std=gp.predict(testFP,return_std=True)
#ensure that the uncertainty is loaded into a float list in order to be sent back to c++
for x in std:
uncertainty.append(float(x))
for x in std:
uncertainty.append(float(x) * float(x))
return uncertainty

当试图从GPR_unc函数(python代码中的第二个函数)导入模块时，python脚本失败。