Hi All I have just started an OpenMP application example in VS2017 platform (/* Boost libs/numeric/odeint/examples/openmp/lorenz_ensemble_simple.cpp). When switch on Properties->C/C++->Language->Open MP Support-> Yes (/openmp), it has a build error Severity Code Description Project File Line Suppression State Error C3016 'i': index variable in OpenMP 'for' statement must have signed integral type OpenMP-test1 c:\users\renfanluo\source\repos\openmp-test1\openmp-test1\openmptest1.cpp 35 If When switch off Properties->C/C++->Language->Open MP Support-> Yes (/openmp) to No (/openmp), then the error goes off. However, "No" means OpenMP is switched off, which is not what I want. It is understood that in the for statement, the variables can be assigned with data type before, the errors associated with these user defined for statement will go off but the similar error shown below remain the same for boost header files. Severity Code Description Project File Line Suppression State Error C3016 'i': index variable in OpenMP 'for' statement must have signed integral type Test-OpenMP2 C:\boost_1_65_1\boost\numeric\odeint\external\openmp\openmp_range_algebra.hpp 72 Could you guys have any ideas of how to fix this problem? Best regards Renfan