Kokkos Node API and Local Linear Algebra Kernels Version of the Day
Tsqr_GlobalTimeStats.cpp
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00005 //          Kokkos: Node API and Parallel Node Kernels
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00043 
00044 #include <Tsqr_GlobalTimeStats.hpp>
00045 #include <Tsqr_MessengerBase.hpp>
00046 
00049 
00050 namespace TSQR {
00051 
00052   TimeStats
00053   globalTimeStats (const Teuchos::RCP< MessengerBase< double > >& comm,
00054        const TimeStats& localStats)
00055   {
00056     TimeStats globalStats;
00057 
00058     // Casting int to double is exact.
00059     const double localCount = static_cast<double> (localStats.count());
00060 
00061     // The counts on all MPI processes should be equal if we are going
00062     // to try to compare them.  We test for this by computing the min
00063     // and max counts (which should be equal) over all processes.
00064     const double minCount = comm->globalMin (localCount);
00065     const double maxCount = comm->globalMax (localCount);
00066     if (minCount != maxCount)
00067       throw std::logic_error ("Global stats don\'t make "
00068             "sense, because counts differ");
00069     // minCount == maxCount, so we can use either one of them.  The
00070     // cast back from double is exact, because the double originally
00071     // came from an int.
00072     const int newCount = static_cast<int> (minCount);
00073       
00074     // Casting int to double is exact.
00075     const double P = static_cast<double> (comm->size());
00076     const double newMin = comm->globalMin (localStats.min());
00077     const double newMax = comm->globalMax (localStats.max());
00078     const double newMean = comm->globalSum (localStats.mean() / P);
00079 
00080     // Note that this is not the sum of the totals of all the
00081     // processes, but rather the "global total."  I've chosen to
00082     // define that as the max of the totals.
00083     const double newTotal = comm->globalMax (localStats.total());
00084 
00085     return TimeStats (newCount, newMin, newMax, newMean, newTotal);
00086   }
00087 
00088 
00089 } // namespace TSQR
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