Hello,   I try to debug my UDA percentile function in cpp and i don't understand the impala operation.   That is my percentile code : template <typename T> StringVal ToStringVal(FunctionContext* context, const T& val) { stringstream ss; ss << val; string str = ss.str(); StringVal string_val(context, str.size()); memcpy(string_val.ptr, str.c_str(), str.size()); return string_val; } template <> StringVal ToStringVal<DoubleVal>(FunctionContext* context, const DoubleVal& val) { if (val.is_null) return StringVal::null(); return ToStringVal(context, val.val); } struct t_percent { int nb; std::list<double> *values; double percent; int64_t count; }; void PercentInit(FunctionContext* context, StringVal* val) { val->is_null = false; val->len = sizeof(t_percent); val->ptr = context->Allocate(val->len); memset(val->ptr, 0, val->len); } void PercentUpdate(FunctionContext* context, const DoubleVal& input,const DoubleVal& percent, StringVal* val) { if (input.is_null || percent.is_null || val->is_null) return; t_percent* avg = reinterpret_cast<t_percent*>(val->ptr); if (avg->values == NULL) avg->values = new std::list<double>(); avg->nb += 1; avg->percent = percent.val; avg->values->push_back(input.val); } void PercentMerge(FunctionContext* context, const StringVal& src, StringVal* dst) { std::cout << "Merge\n"; if (src.is_null || dst->is_null) return; t_percent* src_avg = reinterpret_cast<t_percent*>(src.ptr); t_percent* dst_avg = reinterpret_cast<t_percent*>(dst->ptr); if (dst_avg->values == NULL) dst_avg->values = new std::list<double>(); dst_avg->nb += src_avg->nb; for (std::list<double>::iterator it = src_avg->values->begin(); it != src_avg->values->end(); ++it) dst_avg->values->push_back(*it); } const StringVal PercentSerialize(FunctionContext* context, const StringVal& val) { std::cout << "Serialize\n"; if (val.is_null) return (StringVal::null()); StringVal result(context, val.len); memcpy(result.ptr, val.ptr, val.len); t_percent* avg = reinterpret_cast<t_percent*>(result.ptr); t_percent* old = reinterpret_cast<t_percent*>(val.ptr); avg->values = old->values; context->Free(val.ptr); return result; } StringVal PercentFinalize(FunctionContext* context, const StringVal& val) { std::cout << "Finalize\n"; if (val.is_null) return (StringVal::null()); t_percent* avg = reinterpret_cast<t_percent*>(val.ptr); if (avg->values == NULL || avg->values->empty()) return (StringVal::null()); StringVal result; avg->values->sort(); int n = avg->percent * avg->nb; std::list<double>::iterator it = avg->values->begin(); for (int i = 0; i < n ; ++i) ++it; std::cout << " | n : " << n << " | it : " << *it << " \n"; result = ToStringVal(context, *it); delete(avg->values); context->Free(val.ptr); return result; } That is my Test Code : bool TestPercent() { UdaTestHarness2<StringVal, StringVal, DoubleVal, DoubleVal> test( PercentInit, PercentUpdate, PercentMerge, PercentSerialize, PercentFinalize); vector<DoubleVal> input; vector<DoubleVal> vpercent; for (int i = 0; i < 1001; ++i) { input.push_back(DoubleVal(i)); vpercent.push_back(DoubleVal(0.75)); } if (!test.Execute(input, vpercent, StringVal("750"))) { cerr << "Avg: " << test.GetErrorMsg() << endl; return false; } return true; } int main(int argc, char** argv) { bool passed = true; passed &= TestPercent(); cerr << (passed ? "Tests passed." : "Tests failed.") << endl; return 0; } That is the result: Finalize | n : 750 | it : 750 Serialize Merge Finalize | n : 0 | it : 0 Avg: UDA failed running in one level distributed mode with 1 nodes. Expected: 750 Actual: 0 Tests failed. We can to see, the good results in my first pass of my finalize function, and i don't understand why the program did not finish at that time. And also, my code works with UdaExecutionMode == SINGLE_NODE in parameter of execute test function. If someone can help me in this point, i would appreciate it.   ... View more