[Boost-bugs] [Boost C++ Libraries] #10115: Documentation for Boost MPI gather()

Subject: [Boost-bugs] [Boost C++ Libraries] #10115: Documentation for Boost MPI gather()
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2014-06-11 15:32:27

#10115: Documentation for Boost MPI gather()
-------------------------------------+---------------------
 Reporter:  Max Gerlach <gerlach@…>  |      Owner:  troyer
     Type:  Bugs                     |     Status:  new
Milestone:  To Be Determined         |  Component:  mpi
  Version:  Boost Development Trunk  |   Severity:  Problem
 Keywords:                           |
-------------------------------------+---------------------
 This is the current documentation for gather() [taken from
 github.com/boostorg/mpi/blob/master/include/boost/mpi/collectives.hpp]:

 {{{
 /**
  *  @brief Gather the values stored at every process into a vector at
  *  the root process.
  *
  *  @c gather is a collective algorithm that collects the values
  *  stored at each process into a vector of values at the @p root
  *  process. This vector is indexed by the process number that the
  *  value came from. The type @c T of the values may be any type that
  *  is serializable or has an associated MPI data type.
  *
  *  When the type @c T has an associated MPI data type, this routine
  *  invokes @c MPI_Gather to gather the values.
  *
  *    @param comm The communicator over which the gather will occur.
  *
  *    @param in_value The value to be transmitted by each process. For
  *    gathering arrays of values, @c in_values points to storage for
  *    @c n*comm.size() values.
  *
  *    @param out_values A vector or pointer to storage that will be
  *    populated with the values from each process, indexed by the
  *    process ID number. If it is a vector, it will be resized
  *    accordingly. For non-root processes, this parameter may be
  *    omitted. If it is still provided, however, it will be unchanged.
  *
  *    @param root The process ID number that will collect the
  *    values. This value must be the same on all processes.
  */
 }}}

 Surely the sentence "@c in_values points to storage for @c n*comm.size()
 values" is wrong. in_values only needs to hold n values. However,
 out_values should have storage for n*comm.size() values on the root
 process.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/10115>
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