Frequently Asked Questions

1. What does the following message mean during compilation of zoltan?

   Makefile:28: mem.d: No such file or directory

2. On some platforms, why do Zoltan partitioning methods RCB and RIB use an increasing amount of memory over multiple invocations?
3. Why does compilation of the Fortran90 driver zfdrive fail in fdr_const.f90?

1. What does the following message mean during compilation of Zoltan?

   Makefile:28: mem.d: No such file or directory

   Every time Zoltan is built, gmake looks for a dependency file filename.d for each source file filename.c. The first time Zoltan is built for a given platform, the dependency files do not exist. The dependency files are also removed by "gmake clean." Don't worry, though; after producing this warning, gmake will create the dependency files it needs and continue compilation.

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2. On some platforms, why do Zoltan partitioning methods RCB and RIB use an increasing amount of memory over multiple invocations?

   Zoltan partitioning methods RCB and RIB use MPI_Comm_dup and MPI_Comm_split to recursively create communicators with subsets of processors. Some implementations of MPI (e.g., the default MPI on Sandia's Thunderbird cluster) do not correctly release memory associated with these communicators during MPI_Comm_free, resulting in growing memory use over multiple invocations of RCB or RIB. An undocumented workaround in Zoltan is to set the TFLOPS_SPECIAL parameter to 1 (e.g., Zoltan_Set_Param(zz,"TFLOPS_SPECIAL","1");), which causes an implementation that doesn't use MPI_Comm_split to be invoked.

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3. Why does compilation of the Fortran90 driver zfdrive fail in fdr_const.f90? The Fortran90 driver zfdrive uses user-defined data types for a mesh data structure. It passes these data types to the Zoltan query functions through the void *data argument. Strict type checking in Fortran90 requires that the query interface have these user-defined data types compiled into the interface. The solution is as follows:

   cd Zoltan/fort
   mv zoltan_user_data.f90 zoltan_user_data.f90.zoltan
   ln -s ../fdriver/zoltan_user_data.f90 .
   cd ..
   touch fdriver/zoltan_user_data.f90 fort/zoltan_user_data.f90
   gmake zfdrive
   

   See the Fortran90 API description in the User's Guide and instructions for using zfdrive in the Developer's Guide for more details.