doc/faq/other.tex

   1 \section{Other PPL Tools, Libraries and Applications}
   2
   3 \subsubsection{What is Structured Dagger?}
   4
   5 {\em Structured Dagger} is a structured notation for specifying intra-process
   6 control dependencies in message-driven programs. It combines the efficiency
   7 of message-driven execution with the explicitness of control specification.
   8 Structured Dagger allows easy expression of dependencies among messages
   9 and computations and also among computations within the same object using
  10 {\tt when-blocks}
  11 and various structured constructs. See the Charm++ manual for the details.
  12
  13 \subsubsection{What are the performance problems with AMPI packing and unpacking?}
  14
  15 There is an extra copy involved, because the AMPI message is reusable
  16 immediately after the AMPI call returns. Since Charm++ messages are to
  17 be handed over to the system, there is an extra copy involved (plus creation
  18 of a Charm++ message) while sending.
  19
  20 %<li>
  21 %<b>Why does AMPI now derive from </b><tt>ArrayElement1D</tt><b> rather
  22 %than </b><tt>TempoArray</tt><b>?</b></li>
  23
  24 %<br>Deriving it from <tt>TempoArray</tt> was causing some inefficiencies
  25 %because of the introduction of derived data types. Basically, it was causing
  26 %multiple copies. Also, I felt that some more optimizations, especially
  27 %with collective operations can be done this way, so I have changed AMPI
  28 %to be a standalone Charm++ library, rather than being dependent on Tempo.
  29
  30 \subsubsection{Is {\tt TempoArray::ckTempoSendElem()} the only way for non-AMPI
  31 code to communicate with running AMPI code?}
  32
  33 <br>A static method <tt>sendraw</tt> is added to the AMPI class, that allows
  34 you to send a message to AMPI threads from outside AMPI. So, instead of
  35 using the <tt>TempoArray</tt> method, you can use:
  36 <tt>ampi::sendraw(tag1,tag2,msg,len,arrayid,index);</tt>
  37
  38 \subsubsection{What is Charisma?}
  39
  40 Charisma++ is a prototype language for describing global view of control in a parallel program. It is designed to solve the problem of obscured control flow in the object-based model with Charm++.
  41
  42 \subsubsection{Does Projections use wall time or CPU time?}
  43
  44 Wall time.