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ch_grid20x19
  Simple graph.
  20x19 grid.
  Graph and coordinates included.
  No vertex weights.
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Answers differ for ParMETIS tests on linux platforms 
Suspect difference in rand() is the cause.
On linux, rand() returns values in the range 0 to 2147483647; on
Solaris, it returns values in the range 0 to 32767.  (See definition of
RAND_MAX in <stdlib.h>.)

