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dc814f30da
Number of IO MPI tasks can be varied by selecting which
dimensions use parallel IO and which dimensions use Serial send to boss
I/O.
Thus can neck down from, say 1024 nodes = 4x4x8x8 to {1,8,32,64,128,256,1024} nodes
doing the I/O.
Interpolates nicely between ALL nodes write their data, a single boss per time-plane
in processor space [old UKQCD fortran code did this], and a single node doing all I/O.
Not sure I have the transfer sizes big enough and am not overly convinced fstream
is guaranteed to not give buffer inconsistencies unless I set streambuf size to zero.
Practically it has worked on 8 tasks, 2x1x2x2 writing /cloning NERSC configurations
on my MacOS + OpenMPI and Clang environment.
It is VERY easy to switch to pwrite at a later date, and also easy to send x-strips around from
each node in order to gather bigger chunks at the syscall level.
That would push us up to the circa 8x 18*4*8 == 4KB size write chunk, and by taking, say, x/y non
parallel we get to 16MB contiguous chunks written in multi 4KB transactions
per IOnode in 64^3 lattices for configuration I/O.
I suspect this is fine for system performance.
126 lines
3.8 KiB
C++
126 lines
3.8 KiB
C++
#ifndef GRID_COMMUNICATOR_BASE_H
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#define GRID_COMMUNICATOR_BASE_H
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///////////////////////////////////
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// Processor layout information
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///////////////////////////////////
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#ifdef GRID_COMMS_MPI
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#include <mpi.h>
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#endif
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namespace Grid {
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class CartesianCommunicator {
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public:
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// Communicator should know nothing of the physics grid, only processor grid.
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int _Nprocessors; // How many in all
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std::vector<int> _processors; // Which dimensions get relayed out over processors lanes.
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int _processor; // linear processor rank
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std::vector<int> _processor_coor; // linear processor coordinate
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unsigned long _ndimension;
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#ifdef GRID_COMMS_MPI
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MPI_Comm communicator;
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typedef MPI_Request CommsRequest_t;
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#else
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typedef int CommsRequest_t;
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#endif
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// Constructor
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CartesianCommunicator(const std::vector<int> &pdimensions_in);
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// Wraps MPI_Cart routines
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void ShiftedRanks(int dim,int shift,int & source, int & dest);
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int RankFromProcessorCoor(std::vector<int> &coor);
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void ProcessorCoorFromRank(int rank,std::vector<int> &coor);
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/////////////////////////////////
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// Grid information queries
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/////////////////////////////////
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int IsBoss(void) { return _processor==0; };
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int BossRank(void) { return 0; };
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int ThisRank(void) { return _processor; };
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const std::vector<int> & ThisProcessorCoor(void) { return _processor_coor; };
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const std::vector<int> & ProcessorGrid(void) { return _processors; };
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int ProcessorCount(void) { return _Nprocessors; };
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////////////////////////////////////////////////////////////
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// Reduction
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////////////////////////////////////////////////////////////
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void GlobalSum(RealF &);
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void GlobalSumVector(RealF *,int N);
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void GlobalSum(RealD &);
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void GlobalSumVector(RealD *,int N);
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void GlobalSum(uint32_t &);
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void GlobalSum(ComplexF &c)
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{
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GlobalSumVector((float *)&c,2);
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}
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void GlobalSumVector(ComplexF *c,int N)
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{
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GlobalSumVector((float *)c,2*N);
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}
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void GlobalSum(ComplexD &c)
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{
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GlobalSumVector((double *)&c,2);
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}
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void GlobalSumVector(ComplexD *c,int N)
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{
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GlobalSumVector((double *)c,2*N);
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}
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template<class obj> void GlobalSum(obj &o){
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typedef typename obj::scalar_type scalar_type;
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int words = sizeof(obj)/sizeof(scalar_type);
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scalar_type * ptr = (scalar_type *)& o;
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GlobalSumVector(ptr,words);
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}
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////////////////////////////////////////////////////////////
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// Face exchange, buffer swap in translational invariant way
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////////////////////////////////////////////////////////////
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void SendToRecvFrom(void *xmit,
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int xmit_to_rank,
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void *recv,
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int recv_from_rank,
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int bytes);
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void RecvFrom(void *recv,
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int recv_from_rank,
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int bytes);
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void SendTo(void *xmit,
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int xmit_to_rank,
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int bytes);
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void SendToRecvFromBegin(std::vector<CommsRequest_t> &list,
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void *xmit,
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int xmit_to_rank,
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void *recv,
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int recv_from_rank,
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int bytes);
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void SendToRecvFromComplete(std::vector<CommsRequest_t> &waitall);
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////////////////////////////////////////////////////////////
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// Barrier
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////////////////////////////////////////////////////////////
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void Barrier(void);
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////////////////////////////////////////////////////////////
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// Broadcast a buffer and composite larger
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////////////////////////////////////////////////////////////
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void Broadcast(int root,void* data, int bytes);
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template<class obj> void Broadcast(int root,obj &data)
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{
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Broadcast(root,(void *)&data,sizeof(data));
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};
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static void BroadcastWorld(int root,void* data, int bytes);
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};
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}
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#endif
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