Gather-scatter communication using an MPI neighbourhood collective. The whole halo exchange is carried out by a single MPI_Ineighbor_alltoallv over a distributed-graph communicator built once from the send/recv peer lists. Compared to the point-to-point gs_mpi_t this trades N Isend/Irecv pairs for one collective call: a single entry into the (serialised, on Fugaku) MPI runtime, leaving the library free to stripe the transfers across all network interfaces internally. More...

Inheritance diagram for gs_neighbour::gs_neighbour_t:

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Collaboration diagram for gs_neighbour::gs_neighbour_t:

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Public Member Functions
procedure, pass(this)	init (this, send_pe, recv_pe)
	Initialise the neighbourhood-collective communication method See gs_comm.f90 for details.

procedure, pass(this)	free (this)
	Deallocate the neighbourhood-collective communication method.

procedure, pass(this)	nbsend (this, u, n, tag, deps, strm)
	See gs_comm.f90 for more details on these routines.

procedure, pass(this)	nbrecv (this, tag)
	No-op: the neighbourhood collective issued in nbsend handles both the send and receive directions, so there is nothing to pre-post here.

procedure, pass(this)	nbwait (this, u, n, op, strm)
	Wait for the neighbourhood collective and reduce the received slabs.

procedure, pass(this)	init_vec (this)
	Allocate the fused vector exchange buffers and the nc-scaled collective descriptors, sized for GS_VEC_NC components. Deferred to the first fused exchange, see gs_comm_t. The graph communicator built in init is shared with the scalar exchange and is not touched here, so this stays rank local.

procedure, pass(this)	nbsend_vec (this, u, n, nc, tag, deps, strm)
	Pack the nc components and launch a single neighbourhood collective.

procedure, pass(this)	nbrecv_vec (this, tag, nc)
	No-op: the collective is launched in nbsend_vec.

procedure, pass(this)	nbwait_vec (this, u, n, nc, op, strm)
	Wait for the vector collective and reduce each received slab into u. Peer i's received slab holds nc consecutive blocks of recvcounts(i) values, matching the sender's packing convention.

procedure(gs_comm_init), deferred, pass	init gs_comm_init

procedure(gs_comm_free), deferred, pass	free gs_comm_free

procedure(gs_nbsend), deferred, pass	nbsend gs_nbsend

procedure(gs_nbrecv), deferred, pass	nbrecv gs_nbrecv

procedure(gs_nbwait), deferred, pass	nbwait gs_nbwait

procedure, pass(this)	init_dofs (this)

procedure, pass(this)	free_dofs (this)

procedure, pass(this)	init_order (this, send_pe, recv_pe)
	Obtains which ranks to send and receive data from.

procedure, pass(this)	free_order (this)

procedure, pass(this)	take_schedule (this, src)
	Take over the gather-scatter schedule (dof lists and peer order) of src, avoiding a second (expensive) pass over the connectivity. The data is moved rather than copied, so src is left without a schedule and must not be used for communication afterwards (it can still be freed). No communication resources are set up here; complete the handover with init_schedule once src has been freed, so that the two backends never hold their resources at the same time.

procedure, pass(this)	init_schedule (this)
	Set up this communication method for the schedule taken over by take_schedule. Collective, as init is.

procedure, pass(this)	init_vec (this)
	Fused vector halo exchange. Default implementations abort; backends that set vec_supported = .true. override them.

procedure, pass(this)	nbsend_vec (this, u, n, nc, tag, deps, strm)
	Default fused vector send. Abort unless a backend overrides it.

procedure, pass(this)	nbrecv_vec (this, tag, nc)
	Default fused vector receive. Abort unless a backend overrides it.

procedure, pass(this)	nbwait_vec (this, u, n, nc, op, strm)
	Default fused vector wait/reduce. Abort unless a backend overrides it.

Public Attributes
real(kind=rp), dimension(:), allocatable	send_buf
	Concatenated send slabs, one per peer, in send_pe order.

real(kind=rp), dimension(:), allocatable	recv_buf
	Concatenated recv slabs, one per peer, in recv_pe order.

integer, dimension(:), allocatable	sendcounts
	Per-peer counts and 0-based element displacements for the neighbourhood collective. send_* follow send_pe (the graph destinations), recv_* follow recv_pe (the graph sources).

integer, dimension(:), allocatable	sdispls

integer, dimension(:), allocatable	recvcounts

integer, dimension(:), allocatable	rdispls

type(mpi_comm)	neigh_comm
	Distributed-graph communicator over the halo neighbourhood.

type(mpi_request)	request
	In-flight non-blocking neighbourhood collective.

real(kind=rp), dimension(:), allocatable	send_buf_v
	Fused vector (multi-component) exchange buffers, sized for up to GS_VEC_NC components. Each peer slab holds nc consecutive component blocks. sendcounts_v/sdispls_v etc. are the nc-scaled collective descriptors, filled per call.

real(kind=rp), dimension(:), allocatable	recv_buf_v

integer, dimension(:), allocatable	sendcounts_v

integer, dimension(:), allocatable	sdispls_v

integer, dimension(:), allocatable	recvcounts_v

integer, dimension(:), allocatable	rdispls_v

type(stack_i4_t), dimension(:), allocatable	send_dof
	A list of stacks of dof indices local to this process to send to rank_i.

type(stack_i4_t), dimension(:), allocatable	recv_dof
	recv_dof(rank_i) is a stack of dof indices local to this process to receive from rank_i. size(recv_dof) == pe_size

integer, dimension(:), allocatable	send_pe
	Array of ranks that this process should send to.

integer, dimension(:), allocatable	recv_pe
	array of ranks that this process will receive messages from

logical	vec_supported = .false.
	Whether this backend implements the fused vector (multi-component) halo exchange (nbsend_vec/nbrecv_vec/nbwait_vec). When .false., the gs_op_r3 caller falls back to nc independent scalar exchanges.

logical	vec_ready = .false.
	Whether the buffers the fused vector exchange needs are in place. They are sized GS_VEC_NC times the halo, quadrupling what the backend holds, and only gs_op_r3 ever touches them, so a backend that can allocate them on its own defers that to the first fused exchange (see init_vec) rather than paying for it in every run. A backend whose vector buffers are part of an allocation the whole run has to agree on – symmetric memory, coarrays, registered memory, an RMA window – cannot defer, since a rank with no shared dofs never reaches the first fused exchange; those allocate in init and set this there.

Detailed Description

Definition at line 56 of file gs_neighbour.f90.

Member Function/Subroutine Documentation

◆ free() [1/2]

procedure, pass(this) gs_neighbour::gs_neighbour_t::free ( class(gs_neighbour_t), intent(inout) this )

Definition at line 80 of file gs_neighbour.f90.

◆ free() [2/2]

procedure(gs_comm_free), deferred, pass gs_comm::gs_comm_t::free

pure virtualinherited

Definition at line 82 of file gs_comm.f90.

◆ free_dofs()

procedure, pass(this) gs_comm::gs_comm_t::free_dofs ( class(gs_comm_t), intent(inout) this )

inherited

Definition at line 87 of file gs_comm.f90.

◆ free_order()

procedure, pass(this) gs_comm::gs_comm_t::free_order ( class(gs_comm_t), intent(inout) this )

inherited

Definition at line 89 of file gs_comm.f90.

◆ init() [1/2]

procedure, pass(this) gs_neighbour::gs_neighbour_t::init	(	class(gs_neighbour_t), intent(inout)	this,
		type(stack_i4_t), intent(inout)	send_pe,
		type(stack_i4_t), intent(inout)	recv_pe
	)

Definition at line 79 of file gs_neighbour.f90.

◆ init() [2/2]

procedure(gs_comm_init), deferred, pass gs_comm::gs_comm_t::init

pure virtualinherited

Definition at line 81 of file gs_comm.f90.

◆ init_dofs()

procedure, pass(this) gs_comm::gs_comm_t::init_dofs ( class(gs_comm_t), intent(inout) this )

inherited

Definition at line 86 of file gs_comm.f90.

◆ init_order()

procedure, pass(this) gs_comm::gs_comm_t::init_order	(	class(gs_comm_t), intent(inout)	this,
		type(stack_i4_t), intent(inout)	send_pe,
		type(stack_i4_t), intent(inout)	recv_pe
	)

inherited

Parameters

send_pe,only	contains rank ids this porcesss should send to
recv_pe,only	the ranks this process should receive from

Definition at line 88 of file gs_comm.f90.

◆ init_schedule()

procedure, pass(this) gs_comm::gs_comm_t::init_schedule ( class(gs_comm_t), intent(inout) this )

inherited

Definition at line 91 of file gs_comm.f90.

◆ init_vec() [1/2]

procedure, pass(this) gs_comm::gs_comm_t::init_vec ( class(gs_comm_t), intent(inout) this )

inherited

Note: Rank local by contract: a rank with no shared dofs skips the fused exchange entirely, so an override must not communicate.

Definition at line 94 of file gs_comm.f90.

◆ init_vec() [2/2]

procedure, pass(this) gs_neighbour::gs_neighbour_t::init_vec ( class(gs_neighbour_t), intent(inout) this )

Definition at line 85 of file gs_neighbour.f90.

◆ nbrecv() [1/2]

procedure, pass(this) gs_neighbour::gs_neighbour_t::nbrecv	(	class(gs_neighbour_t), intent(inout)	this,
		integer, intent(in)	tag
	)

Definition at line 83 of file gs_neighbour.f90.

◆ nbrecv() [2/2]

procedure(gs_nbrecv), deferred, pass gs_comm::gs_comm_t::nbrecv

pure virtualinherited

Definition at line 84 of file gs_comm.f90.

◆ nbrecv_vec() [1/2]

procedure, pass(this) gs_comm::gs_comm_t::nbrecv_vec	(	class(gs_comm_t), intent(inout)	this,
		integer, intent(in)	tag,
		integer, intent(in)	nc
	)

inherited

Definition at line 96 of file gs_comm.f90.

◆ nbrecv_vec() [2/2]

procedure, pass(this) gs_neighbour::gs_neighbour_t::nbrecv_vec	(	class(gs_neighbour_t), intent(inout)	this,
		integer, intent(in)	tag,
		integer, intent(in)	nc
	)

Definition at line 87 of file gs_neighbour.f90.

◆ nbsend() [1/2]

procedure, pass(this) gs_neighbour::gs_neighbour_t::nbsend	(	class(gs_neighbour_t), intent(inout)	this,
		real(kind=rp), dimension(n), intent(inout)	u,
		integer, intent(in)	n,
		integer, intent(in)	tag,
		type(c_ptr), intent(inout)	deps,
		type(c_ptr), intent(inout)	strm
	)

Definition at line 82 of file gs_neighbour.f90.

◆ nbsend() [2/2]

procedure(gs_nbsend), deferred, pass gs_comm::gs_comm_t::nbsend

pure virtualinherited

Definition at line 83 of file gs_comm.f90.

◆ nbsend_vec() [1/2]

procedure, pass(this) gs_comm::gs_comm_t::nbsend_vec	(	class(gs_comm_t), intent(inout)	this,
		real(kind=rp), dimension(nc*n), intent(inout)	u,
		integer, intent(in)	n,
		integer, intent(in)	nc,
		integer, intent(in)	tag,
		type(c_ptr), intent(inout)	deps,
		type(c_ptr), intent(inout)	strm
	)

inherited

Parameters

u	compact shared buffer, component-outer: u((c-1)*n + idx)
n	number of shared dofs (per component)
nc	number of components

Definition at line 95 of file gs_comm.f90.

◆ nbsend_vec() [2/2]

procedure, pass(this) gs_neighbour::gs_neighbour_t::nbsend_vec	(	class(gs_neighbour_t), intent(inout)	this,
		real(kind=rp), dimension(nc*n), intent(inout)	u,
		integer, intent(in)	n,
		integer, intent(in)	nc,
		integer, intent(in)	tag,
		type(c_ptr), intent(inout)	deps,
		type(c_ptr), intent(inout)	strm
	)

Parameters

u	compact shared buffer, component-outer: u((c-1)*n + idx). Peer i's slab in send_buf_v holds nc consecutive blocks of sendcounts(i) values, so the collective descriptors are simply nc times the scalar ones.

Definition at line 86 of file gs_neighbour.f90.

◆ nbwait() [1/2]

procedure, pass(this) gs_neighbour::gs_neighbour_t::nbwait	(	class(gs_neighbour_t), intent(inout)	this,
		real(kind=rp), dimension(n), intent(inout)	u,
		integer, intent(in)	n,
		integer	op,
		type(c_ptr), intent(inout)	strm
	)

Definition at line 84 of file gs_neighbour.f90.

◆ nbwait() [2/2]

procedure(gs_nbwait), deferred, pass gs_comm::gs_comm_t::nbwait

pure virtualinherited

Definition at line 85 of file gs_comm.f90.

◆ nbwait_vec() [1/2]

procedure, pass(this) gs_comm::gs_comm_t::nbwait_vec	(	class(gs_comm_t), intent(inout)	this,
		real(kind=rp), dimension(nc*n), intent(inout)	u,
		integer, intent(in)	n,
		integer, intent(in)	nc,
		integer	op,
		type(c_ptr), intent(inout)	strm
	)

inherited

Definition at line 97 of file gs_comm.f90.

◆ nbwait_vec() [2/2]

procedure, pass(this) gs_neighbour::gs_neighbour_t::nbwait_vec	(	class(gs_neighbour_t), intent(inout)	this,
		real(kind=rp), dimension(nc*n), intent(inout)	u,
		integer, intent(in)	n,
		integer, intent(in)	nc,
		integer	op,
		type(c_ptr), intent(inout)	strm
	)

Definition at line 88 of file gs_neighbour.f90.

◆ take_schedule()

procedure, pass(this) gs_comm::gs_comm_t::take_schedule	(	class(gs_comm_t), intent(inout)	this,
		class(gs_comm_t), intent(inout)	src
	)

inherited

Parameters

src	the backend to take the schedule from, left without one

Definition at line 90 of file gs_comm.f90.

Member Data Documentation

◆ neigh_comm

type(mpi_comm) gs_neighbour::gs_neighbour_t::neigh_comm

Definition at line 67 of file gs_neighbour.f90.

◆ rdispls

integer, dimension(:), allocatable gs_neighbour::gs_neighbour_t::rdispls

Definition at line 65 of file gs_neighbour.f90.

◆ rdispls_v

integer, dimension(:), allocatable gs_neighbour::gs_neighbour_t::rdispls_v

Definition at line 77 of file gs_neighbour.f90.

◆ recv_buf

real(kind=rp), dimension(:), allocatable gs_neighbour::gs_neighbour_t::recv_buf

Definition at line 60 of file gs_neighbour.f90.

◆ recv_buf_v

real(kind=rp), dimension(:), allocatable gs_neighbour::gs_neighbour_t::recv_buf_v

Definition at line 75 of file gs_neighbour.f90.

◆ recv_dof

type(stack_i4_t), dimension(:), allocatable gs_comm::gs_comm_t::recv_dof

inherited

Definition at line 58 of file gs_comm.f90.

◆ recv_pe

integer, dimension(:), allocatable gs_comm::gs_comm_t::recv_pe

inherited

Definition at line 64 of file gs_comm.f90.

◆ recvcounts

integer, dimension(:), allocatable gs_neighbour::gs_neighbour_t::recvcounts

Definition at line 65 of file gs_neighbour.f90.

◆ recvcounts_v

integer, dimension(:), allocatable gs_neighbour::gs_neighbour_t::recvcounts_v

Definition at line 77 of file gs_neighbour.f90.

◆ request

type(mpi_request) gs_neighbour::gs_neighbour_t::request

Definition at line 69 of file gs_neighbour.f90.

◆ sdispls

integer, dimension(:), allocatable gs_neighbour::gs_neighbour_t::sdispls

Definition at line 64 of file gs_neighbour.f90.

◆ sdispls_v

integer, dimension(:), allocatable gs_neighbour::gs_neighbour_t::sdispls_v

Definition at line 76 of file gs_neighbour.f90.

◆ send_buf

real(kind=rp), dimension(:), allocatable gs_neighbour::gs_neighbour_t::send_buf

Definition at line 58 of file gs_neighbour.f90.

◆ send_buf_v

real(kind=rp), dimension(:), allocatable gs_neighbour::gs_neighbour_t::send_buf_v

Definition at line 74 of file gs_neighbour.f90.

◆ send_dof

type(stack_i4_t), dimension(:), allocatable gs_comm::gs_comm_t::send_dof

inherited

Definition at line 55 of file gs_comm.f90.

◆ send_pe

integer, dimension(:), allocatable gs_comm::gs_comm_t::send_pe

inherited

Note: : this will usually be fewer than the total number of ranks size(send_pe) <= pe_size

Definition at line 62 of file gs_comm.f90.

◆ sendcounts

integer, dimension(:), allocatable gs_neighbour::gs_neighbour_t::sendcounts

Definition at line 64 of file gs_neighbour.f90.

◆ sendcounts_v

integer, dimension(:), allocatable gs_neighbour::gs_neighbour_t::sendcounts_v

Definition at line 76 of file gs_neighbour.f90.

◆ vec_ready

logical gs_comm::gs_comm_t::vec_ready = .false.

inherited

Definition at line 79 of file gs_comm.f90.

◆ vec_supported

logical gs_comm::gs_comm_t::vec_supported = .false.

inherited

Definition at line 68 of file gs_comm.f90.

The documentation for this type was generated from the following file:

/home/runner/work/neko/neko/src/gs/gs_neighbour.f90

Public Member Functions

Public Attributes

Detailed Description

Member Function/Subroutine Documentation

◆ free() [1/2]

◆ free() [2/2]

◆ free_dofs()

◆ free_order()

◆ init() [1/2]

◆ init() [2/2]

◆ init_dofs()

◆ init_order()

◆ init_schedule()

◆ init_vec() [1/2]

◆ init_vec() [2/2]

◆ nbrecv() [1/2]

◆ nbrecv() [2/2]

◆ nbrecv_vec() [1/2]

◆ nbrecv_vec() [2/2]

◆ nbsend() [1/2]

◆ nbsend() [2/2]

◆ nbsend_vec() [1/2]

◆ nbsend_vec() [2/2]

◆ nbwait() [1/2]

◆ nbwait() [2/2]

◆ nbwait_vec() [1/2]

◆ nbwait_vec() [2/2]

◆ take_schedule()

Member Data Documentation

◆ neigh_comm

◆ rdispls

◆ rdispls_v

◆ recv_buf

◆ recv_buf_v

◆ recv_dof

◆ recv_pe

◆ recvcounts

◆ recvcounts_v

◆ request

◆ sdispls

◆ sdispls_v

◆ send_buf

◆ send_buf_v

◆ send_dof

◆ send_pe

◆ sendcounts

◆ sendcounts_v

◆ vec_ready

◆ vec_supported