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will set the parameter OCT_MAXOBJECTS to 40 in the Zoltan_Struct *zz.
The zoltanParams utility allows applications to specify these parameters in a text file, allowing changes to Zoltan parameters without need to edit source code, recomipile, and relink the applications. A typical situation where this is useful is when trying different partitioning algorithms and parameters to see which works best for a particular application on a particular computer. When using Zoltan's hierarchical balancing procedures (to be included in a future Zoltan release) and when interfacing with the Dynamic Resource Utilization Model (DRUM) to do resource-aware partitioning in heterogeneous and hierarchical parallel computing environments, the number of parameters that may be set makes a tool such as zoltanParams especially useful.
The format of a zoltanParams input file is simple. It contains any number of lines of the format:
ZOLTAN_PARAM PARAM_VALUEwhich is translated into a call to Zoltan_Set_Param, setting the given parameter to the given value.
When used in conjunction with hierarchical balancing (Zoltan method "HIER"), the file format is slightly more complicated. If the parameter is "LB_METHOD" and its value is set to "HIER", the next part of the file is interpreted as hierarchical balancing parameters:
num_levels level 0 partitions for each proc level 0 parameters end with LEVEL END level 1 partitions for each proc level 1 parameters end with LEVEL END ... End file with EOF
To use zoltanParams, an application should replace part of its Zoltan initialization sequence with a zoltanParams call. A typical Zoltan initialization sequence, such as:
/* create zoltan lb object */ lb = Zoltan_Create(MPI_COMM_WORLD); /* register callbacks (not shown) */ /* set zoltan parameters */ Zoltan_Set_Param(lb, "NUM_GID_ENTRIES", "2"); Zoltan_Set_Param(lb, "NUM_LID_ENTRIES", "0"); Zoltan_Set_Param(lb, "OBJ_WEIGHT_DIM", "1"); Zoltan_Set_Param(lb, "EDGE_WEIGHT_DIM", "0"); Zoltan_Set_Param(lb, "RETURN_LISTS", "EXPORT"); Zoltan_Set_Param(lb, "OCT_METHOD", "2"); Zoltan_Set_Param(lb, "OCT_MAXOBJECTS", "40"); Zoltan_Set_Param(lb, "OCT_MINOBJECTS", "10"); Zoltan_Set_Param(lb, "LB_METHOD", "OCTPART");would be replaced by this code:
/* create zoltan lb object */ lb = Zoltan_Create(MPI_COMM_WORLD); /* register callbacks (not shown) */ zoltanParams_read_file(lb, "zoltan.params", MPI_COMM_WORLD);where the file "zoltan.params" in the working directory contains:
NUM_GID_ENTRIES 2 NUM_LID_ENTRIES 0 OBJ_WEIGHT_DIM 1 EDGE_WEIGHT_DIM 0 RETURN_LISTS EXPORT OCT_METHOD 2 OCT_MAXOBJECTS 40 OCT_MINOBJECTS 10 LB_METHOD OCTPARTNote: zoltanParams uses static storage to save hierarchical balancing parameters, and such parameters are stored permanently by zoltanParams_read_file and remain available for use by hierarchical balancing until overridden by a subsequent call to zoltanParams_read_file.