updated hw.tex for hw6

git-svn-id: svn://anubis/gvsu@231 45c1a28c-8058-47b2-ae61-ca45b979098e

cs677/hw6/hw.tex

@@ -21,10 +21,45 @@
 \noindent
 \begin{enumerate}
 \item[1.]{
+    The obvious benefit of using non-blocking communication is that
+    the calling process does not block while the communication is taking
+    place.
+    This leaves the process free to do further computation or work on
+    something else.
+    Another benefit of non-blocking communication is that certain types
+    of deadlocks can be avoided by not having the Send function block
+    until the message is received (for example, when two machines are
+    both doing a send operation followed by a receive operation).
+
+    One challenge to using non-blocking communication is that it is
+    harder to program safely.
+    The programmer must take more care to ensure that data being used
+    in non-blocking communication is not modified while it is being used.
+    A second challenge with using non-blocking communication is that if
+    synchronization is necessary (i.e. the sender wants to know when
+    the message was received), then they must manually poll to obtain
+    this information.
 }
 
 \vskip 1em
 \item[2.]{
+    Assume the mesh size is $n \times n$.
+    Further assume that the node doing the scatter is located in the
+    top left corner of the mesh.
+    First, the total data is divided $n$ ways.
+    1 of these sections are sent to the node doing the scattering,
+    and $n-1$ of these are sent to the next node down.
+    The nodes along the left continue sending data sections down, each
+    taking one section for itself.
+    Then, all of the left edges break each of these $n$ sections into
+    $n$ parts, and repeat the previous process to distribute these
+    $n$ subparts to the nodes to their right.
+
+    This method will take $2n$ steps to complete.
+    The message transfer size is not fixed.
+    The messages at the beginning (closer to the scattering node)
+    are larger and subsequent messages get smaller and smaller as
+    they get further from the scattering node.
 }