[Mpi3-rma] MPI RMW operations

[Rajeev Thakur]

Some comments:

* Are the semantics supposed to be that the original value at the target is
read and stored at the result_addr on the origin (like a Get), and the
target memory is updated with the result of the reduction operation (like
Accumulate)? 

* What are the semantics of the two-operand versions?

* Why is there no count, datatype at the target like in Accumulate?

* When assert == MPI_MODE_PASSIVE_EPOCH_IMPLICIT, what is the lock type for
the Win_lock -- shared or exclusive? Also, Win_unlock takes only two
parameters.

* Regarding the interaction with explicit epochs of Rmw when assert ==
MPI_MODE_PASSIVE_EPOCH_IMPLICIT, it should be the same as the interaction of
its equivalent sequence, namely, Lock - Rmw - Unlock. In other words, there
shouldn't be another epoch around it on the same process (nested epochs not
allowed), and the epochs on other processes must not conflict.

Rajeev


> -----Original Message-----
> From: mpi3-rma-bounces at lists.mpi-forum.org 
> [mailto:mpi3-rma-bounces at lists.mpi-forum.org] On Behalf Of 
> Shipman, Galen M.
> Sent: Monday, March 24, 2008 10:10 PM
> To: mpi3-rma at lists.mpi-forum.org
> Subject: [Mpi3-rma] MPI RMW operations
> 
> 
> Howard and I have been working on the RMW operations listed 
> below for  
> consideration.
> 
> - Galen Shipman - ORNL
> 
> 
> Single operand RMW operations
> 
> MPI_Rmw(void *operand_addr,
>                      int count,
> 	            MPI_Datatype datatype,
> 	            void *result_addr,
> 	            int target_rank,
> 	            MPI_Aint target_disp,
> 	            int assert,
> 	            MPI_RMW_Op op,
>                      MPI_Win win)
> 
> 
> Two operand RMW operations
> 	
> MPI_Rmw2(void *operand_addr,
>                        int count,
>                        MPI_Datatype datatype,
> 	              void *operand2_addr,
> 	              void *result_addr,
> 	              int target_rank,
> 	              MPI_Aint target_disp,
>                        int assert,
> 	              MPI_RMW_2_Op op,
>                        MPI_Win win)
> 
> 
> 
> MPI_RMW_Op Predefined RMW single operand operations
> The following predefined operations are supplied for MPI_RMW 
> and related
> functions. These operations are invoked  by placing the 
> following in op.
> 
> Name		 Meaning
> 
> MPI_RMW_INC		increment
> MPI_RMW_PROD	product
> MPI_RMW_SUM		sum
> MPI_RMW_LAND	logical and
> MPI_RMW_LOR		logical or
> MPI_RMW_LXOR	logical xor
> MPI_RMW_BAND	binary and
> MPI_RMW_BOR		binary or
> MPI_RMW_BXOR	binary xor
> MPI_RMW_SWAP	swap value
> 
> MPI_RMW_2_Op Predefined RMW two operand operations
> 
> Name						Meaning
> 
> MPI_RMW2_MASK_SWAP	swap masked bits
> MPI_RMW2_COMP_SWAP	compare and swap
> 
> Note: MPI_RMW2_COMP_SWAP is an equality comparison, we may wish to  
> consider multiple comparison operations such as >, >=, <, <=, ==, <>.
> 
> Both MPI_Rmw and MPI_Rmw2 take an assert argument.
> When assert == MPI_MODE_PASSIVE_EPOCH_IMPLICIT MPI_Rmw/2 is  
> equivalent to:
> 
> MPI_Win_lock(target_rank,0,win);
> MPI_Rmw(.....);
> MPI_Win_unlock(target_rank,0,win);
> 
> When assert  == MPI_MODE_PASSIVE_EPOCH_IMPLICIT | MPI_MODE_NOCHECK  
> the MPI library knows that the window lock at the target need not be  
> acquired.
> 
> 
> 
> 
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