MueLu: Failure to build parallel on Windows-LLVM due to lack of inet_network

[jrobcary]

Bug Report

@trilinos/muelu

The build fails as shown at the bottom. This is due to using inet_network, which does not exist on Windows.

This whole function seems to be about

// Generates a communicator whose only members are other ranks of the baseComm on my node

Would not this be done directly with a call to

int ierr = MPI_Comm_split_type(baseComm, MPI_COMM_TYPE_SHARED,
0, MPI_INFO_NULL, &newComm);

????

        C:\PROGRA~1\LLVM\bin\clang-cl.exe @C:\cygwin64\tmp\nmE0F2.tmp
D:\winsame\cary\vorpalall-dev2\trilinos\packages\muelu\src\Utils\MueLu_Utilities.cpp(271,32): warning: 'gethostbyname' is deprecated: Use getaddrinfo() or GetAddrInfoW() instead or define _WINSOCK_DEPRECATED_NO_WARNINGS to disable deprecated API warnings [-Wdeprecated-declarations]
       struct hostent * host = gethostbyname(hostname);
                               ^
C:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\um\winsock2.h(2215,1): note: 'gethostbyname' has been explicitly marked deprecated here
_WINSOCK_DEPRECATED_BY("getaddrinfo() or GetAddrInfoW()")
^
C:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\um\winsock2.h(26,56): note: expanded from macro '_WINSOCK_DEPRECATED_BY'
#define _WINSOCK_DEPRECATED_BY(replacement) __declspec(deprecated("Use " replacement " instead or define _WINSOCK_DEPRECATED_NO_WARNINGS to disable deprecated API warnings"))
                                                       ^
D:\winsame\cary\vorpalall-dev2\trilinos\packages\muelu\src\Utils\MueLu_Utilities.cpp(272,33): error: use of undeclared identifier 'inet_network'; did you mean 'inet_ntoa'?
       int myaddr = (int) htonl(inet_network(inet_ntoa(*(struct in_addr *)host->h_addr)));
                                ^~~~~~~~~~~~
                                inet_ntoa
C:\Program Files (x86)\Windows Kits\10\include\10.0.18362.0\um\winsock2.h(1849,1): note: 'inet_ntoa' declared here
inet_ntoa(
^
D:\winsame\cary\vorpalall-dev2\trilinos\packages\muelu\src\Utils\MueLu_Utilities.cpp(272,46): error: no viable conversion from 'char *' to 'struct in_addr'
       int myaddr = (int) htonl(inet_network(inet_ntoa(*(struct in_addr *)host->h_addr)));

[cgcgcg]

@csiefer2

[cgcgcg]

I guess MPI_COMM_TYPE_SHARED works only for MPI>=3.

[jrobcary]

Dunno your targets, but it works for us with OpenMPI-4.0.5, mpich-3.3.2, Windows-MPI, current version.

[jhux2]

@trilinos/muelu

[jrobcary]

It looks like inet_ntoa gives a string containing the dot notation.
inet_network converts this to a number in host byte order
htonl converts this to network byte order.

But then one could use just inet_addr?
"The inet_addr() function converts the Internet host address cp from IPv4 numbers-and-dots notation into binary data in network byte order."

I changed the code to

#ifdef _WIN32
       int myaddr = (int) inet_addr(inet_ntoa(*(struct in_addr *)host->h_addr));
#else
       int myaddr = (int) htonl(inet_network(inet_ntoa(*(struct in_addr *)host->h_addr)));
#endif

and it does compile.

Since the _WIN32 line does compile on both Linux and Windows, is it okay to just submit that change to the test system?

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[jrobcary]

This is now building.