Exercise E7:

• Implement the parallel program bw using MPI_Scatterv and MPI_Gatherv. As starting point you can use the serial version. It has to be compiled together with pic.c, for example by typing
  > gcc sbw.c pic.c -o sbw
  The required definitions are contained in pic.h which has to be copied to the same place as pic.c and sbw.c. You can run the serial program sbw with
  > sbw figurein.pnm figureout.pnm
  where figurein.pnm is a pnm color file and figureout.pnm is the name of the black and white picture which is calculated in sbw.
• Detailed instructions on how to use the picture i/o routines are given in the file pic.h.
• Test your parallel program with different pictures, for example
  
  You can convert the format from jpg to pnm for example with the program gimp, or xv, or simply with
  > jpegtopnm porsche.jpg > porsche.pnm
  
• Determine the speedup of your code compared to the serial version.

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