Nektar::LibUtilities::CommMpi Class Reference

A global linear system. More...

#include <CommMpi.h>

Inheritance diagram for Nektar::LibUtilities::CommMpi:

Public Member Functions
	CommMpi (int narg, char *arg[])
virtual	~CommMpi ()
MPI_Comm	GetComm ()
Public Member Functions inherited from Nektar::LibUtilities::Comm
	Comm (int narg, char *arg[])
virtual	~Comm ()
void	Finalise ()
int	GetSize ()
	Returns number of processes. More...
int	GetRank ()
const std::string &	GetType () const
void	Block ()
	Block execution until all processes reach this point. More...
NekDouble	Wtime ()
	Return the time in seconds. More...
template<class T >
void	Send (int pProc, T &pData)
template<class T >
void	Recv (int pProc, T &pData)
template<class T >
void	SendRecv (int pSendProc, T &pSendData, int pRecvProc, T &pRecvData)
template<class T >
void	SendRecvReplace (int pSendProc, int pRecvProc, T &pData)
template<class T >
void	AllReduce (T &pData, enum ReduceOperator pOp)
template<class T >
void	AlltoAll (T &pSendData, T &pRecvData)
template<class T1 , class T2 >
void	AlltoAllv (T1 &pSendData, T2 &pSendDataSizeMap, T2 &pSendDataOffsetMap, T1 &pRecvData, T2 &pRecvDataSizeMap, T2 &pRecvDataOffsetMap)
template<class T >
void	AllGather (T &pSendData, T &pRecvData)
template<class T >
void	AllGatherv (T &pSendData, T &pRecvData, Array< OneD, int > &pRecvDataSizeMap, Array< OneD, int > &pRecvDataOffsetMap)
template<class T >
void	AllGatherv (T &pRecvData, Array< OneD, int > &pRecvDataSizeMap, Array< OneD, int > &pRecvDataOffsetMap)
template<class T >
void	Bcast (T &data, int rootProc)
template<class T >
void	Exscan (T &pData, const enum ReduceOperator pOp, T &ans)
template<class T >
T	Gather (const int rootProc, T &val)
template<class T >
T	Scatter (const int rootProc, T &pData)
CommSharedPtr	CommCreateIf (int flag)
	If the flag is non-zero create a new communicator. More...
void	SplitComm (int pRows, int pColumns)
	Splits this communicator into a grid of size pRows*pColumns and creates row and column communicators. By default the communicator is a single row. More...
CommSharedPtr	GetRowComm ()
	Retrieve the row communicator to which this process belongs. More...
CommSharedPtr	GetColumnComm ()
	Retrieve the column communicator to which this process belongs. More...
bool	TreatAsRankZero (void)
bool	IsSerial (void)
bool	RemoveExistingFiles (void)

Static Public Member Functions
static CommSharedPtr	create (int narg, char *arg[])
	Creates an instance of this class. More...

Static Public Attributes
static std::string	className
	Name of class. More...

Protected Member Functions
	CommMpi (MPI_Comm pComm)
	CommMpi ()
virtual void	v_Finalise ()
virtual int	v_GetRank ()
virtual void	v_Block ()
virtual double	v_Wtime ()
virtual bool	v_TreatAsRankZero (void)
virtual bool	v_IsSerial (void)
virtual void	v_Send (void *buf, int count, CommDataType dt, int dest)
virtual void	v_Recv (void *buf, int count, CommDataType dt, int source)
virtual void	v_SendRecv (void *sendbuf, int sendcount, CommDataType sendtype, int dest, void *recvbuf, int recvcount, CommDataType recvtype, int source)
virtual void	v_SendRecvReplace (void *buf, int count, CommDataType dt, int pSendProc, int pRecvProc)
virtual void	v_AllReduce (void *buf, int count, CommDataType dt, enum ReduceOperator pOp)
virtual void	v_AlltoAll (void *sendbuf, int sendcount, CommDataType sendtype, void *recvbuf, int recvcount, CommDataType recvtype)
virtual void	v_AlltoAllv (void *sendbuf, int sendcounts[], int sensdispls[], CommDataType sendtype, void *recvbuf, int recvcounts[], int rdispls[], CommDataType recvtype)
virtual void	v_AllGather (void *sendbuf, int sendcount, CommDataType sendtype, void *recvbuf, int recvcount, CommDataType recvtype)
virtual void	v_AllGatherv (void *sendbuf, int sendcount, CommDataType sendtype, void *recvbuf, int recvcounts[], int rdispls[], CommDataType recvtype)
virtual void	v_AllGatherv (void *recvbuf, int recvcounts[], int rdispls[], CommDataType recvtype)
virtual void	v_Bcast (void *buffer, int count, CommDataType dt, int root)
virtual void	v_Exscan (Array< OneD, unsigned long long > &pData, const enum ReduceOperator pOp, Array< OneD, unsigned long long > &ans)
virtual void	v_Gather (void *sendbuf, int sendcount, CommDataType sendtype, void *recvbuf, int recvcount, CommDataType recvtype, int root)
virtual void	v_Scatter (void *sendbuf, int sendcount, CommDataType sendtype, void *recvbuf, int recvcount, CommDataType recvtype, int root)
virtual void	v_SplitComm (int pRows, int pColumns)
virtual CommSharedPtr	v_CommCreateIf (int flag)
Protected Member Functions inherited from Nektar::LibUtilities::Comm
	Comm ()
virtual bool	v_RemoveExistingFiles (void)

Protected Attributes
MPI_Comm	m_comm
int	m_rank
Protected Attributes inherited from Nektar::LibUtilities::Comm
int	m_size
	Number of processes. More...
std::string	m_type
	Type of communication. More...
CommSharedPtr	m_commRow
	Row communicator. More...
CommSharedPtr	m_commColumn
	Column communicator. More...

Detailed Description

A global linear system.

Definition at line 60 of file CommMpi.h.

Constructor & Destructor Documentation

CommMpi() [1/3]

Nektar::LibUtilities::CommMpi::CommMpi	(	int	narg,
		char *	arg[]
	)

Definition at line 52 of file CommMpi.cpp.

References ASSERTL0, m_comm, m_rank, Nektar::LibUtilities::Comm::m_size, and Nektar::LibUtilities::Comm::m_type.

                                      : Comm(narg, arg)
{
    int init = 0;
    MPI_Initialized(&init);
    ASSERTL0(!init, "MPI has already been initialised.");

    int retval = MPI_Init(&narg, &arg);
    if (retval != MPI_SUCCESS)
    {
        ASSERTL0(false, "Failed to initialise MPI");
    }

    m_comm = MPI_COMM_WORLD;
    MPI_Comm_size(m_comm, &m_size);
    MPI_Comm_rank(m_comm, &m_rank);

#ifdef NEKTAR_USING_PETSC
    PetscInitializeNoArguments();
#endif

    m_type = "Parallel MPI";
}

~CommMpi()

Nektar::LibUtilities::CommMpi::~CommMpi ( )

virtual

Definition at line 90 of file CommMpi.cpp.

References m_comm.

{
    int flag;
    MPI_Finalized(&flag);
    if (!flag && m_comm != MPI_COMM_WORLD)
    {
        MPI_Comm_free(&m_comm);
    }
}

CommMpi() [2/3]

Nektar::LibUtilities::CommMpi::CommMpi ( MPI_Comm  pComm )

protected

Definition at line 78 of file CommMpi.cpp.

References m_comm, m_rank, Nektar::LibUtilities::Comm::m_size, and Nektar::LibUtilities::Comm::m_type.

                               : Comm()
{
    m_comm = pComm;
    MPI_Comm_size(m_comm, &m_size);
    MPI_Comm_rank(m_comm, &m_rank);

    m_type = "Parallel MPI";
}

CommMpi() [3/3]

Nektar::LibUtilities::CommMpi::CommMpi ( )

inlineprotected

Definition at line 84 of file CommMpi.h.

References v_AllGather(), v_AllGatherv(), v_AllReduce(), v_AlltoAll(), v_AlltoAllv(), v_Bcast(), v_Block(), v_CommCreateIf(), v_Exscan(), v_Finalise(), v_Gather(), v_GetRank(), v_IsSerial(), v_Recv(), v_Scatter(), v_Send(), v_SendRecv(), v_SendRecvReplace(), v_SplitComm(), v_TreatAsRankZero(), and v_Wtime().

Referenced by v_CommCreateIf(), and v_SplitComm().

    {};

Member Function Documentation

create()

static CommSharedPtr Nektar::LibUtilities::CommMpi::create ( int  narg, char *  arg[]  )

inlinestatic

Creates an instance of this class.

Definition at line 64 of file CommMpi.h.

References Nektar::MemoryManager< DataType >::AllocateSharedPtr().

    {
        return MemoryManager<CommMpi>::AllocateSharedPtr(narg, arg);
    }

GetComm()

MPI_Comm Nektar::LibUtilities::CommMpi::GetComm

(

)

Definition at line 103 of file CommMpi.cpp.

References m_comm.

Referenced by Nektar::MultiRegions::GlobalLinSysPETSc::GlobalLinSysPETSc().

{
    return m_comm;
}

v_AllGather()

void Nektar::LibUtilities::CommMpi::v_AllGather ( void *  sendbuf, int  sendcount, CommDataType  sendtype, void *  recvbuf, int  recvcount, CommDataType  recvtype  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 292 of file CommMpi.cpp.

References ASSERTL0, and m_comm.

Referenced by CommMpi().

{
    int retval = MPI_Allgather(sendbuf, sendcount, sendtype, recvbuf, recvcount,
                               recvtype, m_comm);

    ASSERTL0(retval == MPI_SUCCESS, "MPI error performing Allgather.");
}

v_AllGatherv() [1/2]

void Nektar::LibUtilities::CommMpi::v_AllGatherv ( void *  sendbuf, int  sendcount, CommDataType  sendtype, void *  recvbuf, int  recvcounts[], int  rdispls[], CommDataType  recvtype  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 301 of file CommMpi.cpp.

References ASSERTL0, and m_comm.

Referenced by CommMpi().

{
    int retval = MPI_Allgatherv(sendbuf, sendcount, sendtype, recvbuf,
                                recvcounts, rdispls, recvtype, m_comm);

    ASSERTL0(retval == MPI_SUCCESS, "MPI error performing Allgather.");
}

v_AllGatherv() [2/2]

void Nektar::LibUtilities::CommMpi::v_AllGatherv ( void *  recvbuf, int  recvcounts[], int  rdispls[], CommDataType  recvtype  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 311 of file CommMpi.cpp.

References ASSERTL0, and m_comm.

{
    int retval = MPI_Allgatherv(MPI_IN_PLACE, 0, MPI_DATATYPE_NULL, recvbuf,
                                recvcounts, rdispls, recvtype, m_comm);

    ASSERTL0(retval == MPI_SUCCESS, "MPI error performing Allgatherv.");
}

v_AllReduce()

void Nektar::LibUtilities::CommMpi::v_AllReduce ( void *  buf, int  count, CommDataType  dt, enum ReduceOperator  pOp  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 236 of file CommMpi.cpp.

References ASSERTL0, Nektar::LibUtilities::Comm::GetSize(), m_comm, Nektar::LibUtilities::ReduceMax, Nektar::LibUtilities::ReduceMin, and Nektar::LibUtilities::ReduceSum.

Referenced by CommMpi().

{
    if (GetSize() == 1)
    {
        return;
    }

    MPI_Op vOp;
    switch (pOp)
    {
        case ReduceMax:
            vOp = MPI_MAX;
            break;
        case ReduceMin:
            vOp = MPI_MIN;
            break;
        case ReduceSum:
        default:
            vOp = MPI_SUM;
            break;
    }
    int retval = MPI_Allreduce(MPI_IN_PLACE, buf, count, dt, vOp, m_comm);

    ASSERTL0(retval == MPI_SUCCESS, "MPI error performing All-reduce.");
}

v_AlltoAll()

void Nektar::LibUtilities::CommMpi::v_AlltoAll ( void *  sendbuf, int  sendcount, CommDataType  sendtype, void *  recvbuf, int  recvcount, CommDataType  recvtype  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 266 of file CommMpi.cpp.

References ASSERTL0, and m_comm.

Referenced by CommMpi().

{
    int retval = MPI_Alltoall(sendbuf, sendcount, sendtype, recvbuf, recvcount,
                              recvtype, m_comm);

    ASSERTL0(retval == MPI_SUCCESS, "MPI error performing All-to-All.");
}

v_AlltoAllv()

void Nektar::LibUtilities::CommMpi::v_AlltoAllv ( void *  sendbuf, int  sendcounts[], int  sensdispls[], CommDataType  sendtype, void *  recvbuf, int  recvcounts[], int  rdispls[], CommDataType  recvtype  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 278 of file CommMpi.cpp.

References ASSERTL0, and m_comm.

Referenced by CommMpi().

{
    int retval = MPI_Alltoallv(sendbuf, sendcounts, sdispls, sendtype, recvbuf,
                               recvcounts, rdispls, recvtype, m_comm);

    ASSERTL0(retval == MPI_SUCCESS, "MPI error performing All-to-All-v.");
}

v_Bcast()

void Nektar::LibUtilities::CommMpi::v_Bcast ( void *  buffer, int  count, CommDataType  dt, int  root  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 320 of file CommMpi.cpp.

References ASSERTL0, and m_comm.

Referenced by CommMpi().

{
    int retval = MPI_Bcast(buffer, count, dt, root, m_comm);
    ASSERTL0(retval == MPI_SUCCESS, "MPI error performing Bcast-v.");
}

v_Block()

void Nektar::LibUtilities::CommMpi::v_Block ( )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 166 of file CommMpi.cpp.

References m_comm.

Referenced by CommMpi().

{
    MPI_Barrier(m_comm);
}

v_CommCreateIf()

CommSharedPtr Nektar::LibUtilities::CommMpi::v_CommCreateIf ( int  flag )

protectedvirtual

Create a new communicator if the flag is non-zero.

Implements Nektar::LibUtilities::Comm.

Definition at line 405 of file CommMpi.cpp.

References CommMpi(), and m_comm.

Referenced by CommMpi().

{
    MPI_Comm newComm;
    // color == MPI_UNDEF => not in the new communicator
    // key == 0 on all => use rank to order them. OpenMPI, at least,
    // implies this is faster than ordering them ourselves.
    MPI_Comm_split(m_comm, flag ? 0 : MPI_UNDEFINED, 0, &newComm);

    if (flag == 0)
    {
        // flag == 0 => get back MPI_COMM_NULL, return a null ptr instead.
        return std::shared_ptr<Comm>();
    }
    else
    {
        // Return a real communicator
        return std::shared_ptr<Comm>(new CommMpi(newComm));
    }
}

v_Exscan()

void Nektar::LibUtilities::CommMpi::v_Exscan ( Array< OneD, unsigned long long > &  pData, const enum ReduceOperator  pOp, Array< OneD, unsigned long long > &  ans  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 326 of file CommMpi.cpp.

References ASSERTL0, m_comm, Nektar::LibUtilities::MPI_UNSIGNED_LONG_LONG, Nektar::LibUtilities::ReduceMax, Nektar::LibUtilities::ReduceMin, and Nektar::LibUtilities::ReduceSum.

Referenced by CommMpi().

{
    int n = pData.num_elements();
    ASSERTL0(n == ans.num_elements(), "Array sizes differ in Exscan");

    MPI_Op vOp;
    switch (pOp)
    {
        case ReduceMax:
            vOp = MPI_MAX;
            break;
        case ReduceMin:
            vOp = MPI_MIN;
            break;
        case ReduceSum:
        default:
            vOp = MPI_SUM;
            break;
    }

    int retval = MPI_Exscan(pData.get(), ans.get(), n, MPI_UNSIGNED_LONG_LONG,
                            vOp, m_comm);
    ASSERTL0(retval == MPI_SUCCESS, "MPI error performing Exscan-v.");
}

v_Finalise()

void Nektar::LibUtilities::CommMpi::v_Finalise ( )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Reimplemented in Nektar::LibUtilities::CommCwipi.

Definition at line 111 of file CommMpi.cpp.

Referenced by CommMpi(), and Nektar::LibUtilities::CommCwipi::v_Finalise().

{
#ifdef NEKTAR_USING_PETSC
    PetscFinalize();
#endif
    int flag;
    MPI_Finalized(&flag);
    if (!flag)
    {
        MPI_Finalize();
    }
}

v_Gather()

void Nektar::LibUtilities::CommMpi::v_Gather ( void *  sendbuf, int  sendcount, CommDataType  sendtype, void *  recvbuf, int  recvcount, CommDataType  recvtype, int  root  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 353 of file CommMpi.cpp.

References ASSERTL0, and m_comm.

Referenced by CommMpi().

{
    int retval = MPI_Gather(sendbuf, sendcount, sendtype, recvbuf, recvcount,
                            recvtype, root, m_comm);

    ASSERTL0(retval == MPI_SUCCESS, "MPI error performing Gather.");
}

v_GetRank()

int Nektar::LibUtilities::CommMpi::v_GetRank ( void  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 127 of file CommMpi.cpp.

References m_rank.

Referenced by CommMpi().

{
    return m_rank;
}

v_IsSerial()

bool Nektar::LibUtilities::CommMpi::v_IsSerial ( void  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 151 of file CommMpi.cpp.

References Nektar::LibUtilities::Comm::m_size.

Referenced by CommMpi().

{
    if(m_size == 1)
    {
        return true;
    }
    else
    {
        return false;
    }
}

v_Recv()

void Nektar::LibUtilities::CommMpi::v_Recv ( void *  buf, int  count, CommDataType  dt, int  source  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 197 of file CommMpi.cpp.

References m_comm.

Referenced by CommMpi().

{
    MPI_Recv(buf, count, dt, source, 0, m_comm, MPI_STATUS_IGNORE);
    // ASSERTL0(status.MPI_ERROR == MPI_SUCCESS,
    //         "MPI error receiving data.");
}

v_Scatter()

void Nektar::LibUtilities::CommMpi::v_Scatter ( void *  sendbuf, int  sendcount, CommDataType  sendtype, void *  recvbuf, int  recvcount, CommDataType  recvtype, int  root  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 363 of file CommMpi.cpp.

References ASSERTL0, and m_comm.

Referenced by CommMpi().

{
    int retval = MPI_Scatter(sendbuf, sendcount, sendtype, recvbuf, recvcount,
                             recvtype, root, m_comm);
    ASSERTL0(retval == MPI_SUCCESS, "MPI error performing Scatter.");
}

v_Send()

void Nektar::LibUtilities::CommMpi::v_Send ( void *  buf, int  count, CommDataType  dt, int  dest  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 182 of file CommMpi.cpp.

References m_comm, and MPISYNC.

Referenced by CommMpi().

{
    if (MPISYNC)
    {
        MPI_Ssend(buf, count, dt, dest, 0, m_comm);
    }
    else
    {
        MPI_Send(buf, count, dt, dest, 0, m_comm);
    }
}

v_SendRecv()

void Nektar::LibUtilities::CommMpi::v_SendRecv ( void *  sendbuf, int  sendcount, CommDataType  sendtype, int  dest, void *  recvbuf, int  recvcount, CommDataType  recvtype, int  source  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 207 of file CommMpi.cpp.

References ASSERTL0, and m_comm.

Referenced by CommMpi().

{
    MPI_Status status;
    int retval = MPI_Sendrecv(sendbuf, sendcount, sendtype, dest, 0, recvbuf,
                              recvcount, recvtype, source, 0, m_comm, &status);

    ASSERTL0(retval == MPI_SUCCESS,
             "MPI error performing send-receive of data.");
}

v_SendRecvReplace()

void Nektar::LibUtilities::CommMpi::v_SendRecvReplace ( void *  buf, int  count, CommDataType  dt, int  pSendProc, int  pRecvProc  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 222 of file CommMpi.cpp.

References ASSERTL0, and m_comm.

Referenced by CommMpi().

{
    MPI_Status status;
    int retval = MPI_Sendrecv_replace(buf, count, dt, pRecvProc, 0, pSendProc,
                                      0, m_comm, &status);

    ASSERTL0(retval == MPI_SUCCESS,
             "MPI error performing Send-Receive-Replace of data.");
}

v_SplitComm()

void Nektar::LibUtilities::CommMpi::v_SplitComm ( int  pRows, int  pColumns  )

protectedvirtual

Processes are considered as a grid of size pRows*pColumns. Comm objects are created corresponding to the rows and columns of this grid. The row and column to which this process belongs is stored in m_commRow and m_commColumn.

Implements Nektar::LibUtilities::Comm.

Definition at line 378 of file CommMpi.cpp.

References ASSERTL0, CommMpi(), m_comm, Nektar::LibUtilities::Comm::m_commColumn, Nektar::LibUtilities::Comm::m_commRow, m_rank, and Nektar::LibUtilities::Comm::m_size.

Referenced by CommMpi().

{
    ASSERTL0(pRows * pColumns == m_size,
             "Rows/Columns do not match comm size.");

    MPI_Comm newComm;

    // Compute row and column in grid.
    int myCol = m_rank % pColumns;
    int myRow = (m_rank - myCol) / pColumns;

    // Split Comm into rows - all processes with same myRow are put in
    // the same communicator. The rank within this communicator is the
    // column index.
    MPI_Comm_split(m_comm, myRow, myCol, &newComm);
    m_commRow = std::shared_ptr<Comm>(new CommMpi(newComm));

    // Split Comm into columns - all processes with same myCol are put
    // in the same communicator. The rank within this communicator is
    // the row index.
    MPI_Comm_split(m_comm, myCol, myRow, &newComm);
    m_commColumn = std::shared_ptr<Comm>(new CommMpi(newComm));
}

v_TreatAsRankZero()

bool Nektar::LibUtilities::CommMpi::v_TreatAsRankZero ( void  )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 135 of file CommMpi.cpp.

References m_rank.

Referenced by CommMpi().

{
    if (m_rank == 0)
    {
        return true;
    }
    else
    {
        return false;
    }
    return true;
}

v_Wtime()

double Nektar::LibUtilities::CommMpi::v_Wtime ( )

protectedvirtual

Implements Nektar::LibUtilities::Comm.

Definition at line 174 of file CommMpi.cpp.

Referenced by CommMpi().

{
    return MPI_Wtime();
}

Member Data Documentation

className

std::string Nektar::LibUtilities::CommMpi::className

static

Initial value:

= GetCommFactory().RegisterCreatorFunction(
    "ParallelMPI", CommMpi::create, "Parallel communication using MPI.")

Name of class.

Definition at line 70 of file CommMpi.h.

m_comm

MPI_Comm Nektar::LibUtilities::CommMpi::m_comm

protected

Definition at line 79 of file CommMpi.h.

Referenced by Nektar::LibUtilities::CommCwipi::CommCwipi(), CommMpi(), GetComm(), v_AllGather(), v_AllGatherv(), v_AllReduce(), v_AlltoAll(), v_AlltoAllv(), v_Bcast(), v_Block(), v_CommCreateIf(), v_Exscan(), v_Gather(), v_Recv(), v_Scatter(), v_Send(), v_SendRecv(), v_SendRecvReplace(), v_SplitComm(), and ~CommMpi().

m_rank

int Nektar::LibUtilities::CommMpi::m_rank

protected

Definition at line 80 of file CommMpi.h.

Referenced by Nektar::LibUtilities::CommCwipi::CommCwipi(), CommMpi(), v_GetRank(), v_SplitComm(), and v_TreatAsRankZero().