The XPI Interface

Center for Computation & Technology @ Louisiana State University - http://cct.lsu.edu/Center for Computation & Technology @ Louisiana State University - http://cct.lsu.edu/

ParalleX / XPI Specification - http://parallex.cct.lsu.edu ParalleX / XPI Specification - http://parallex.cct.lsu.edu

The XPI Interface



Early thoughts on the XPI RepresentationWill be updated/changed frequently



Goals

• Provide Programming Execution Model• Functionality: ParalleX / HPX• Speed: Incur minimal overhead• Interface: Similar to MPI when possible• Small: minimal set of functions and objects



Things We Rely on Being Fast• Remote Direct Memory Addressing• Light Weight Threads• Active Messages (Parcels)• Atomic Memory Operations• Work Queues



LCO• Constructor

– In: receptor, byte_array• get_gid

– Out: GID• free



LCO

• waitany # listen to multiple lco's• counted_waitany # listen to multiple lco's



LCO• write # possibly remote operation

– In: byte_array– In: Offset– In: Len

• wait # local, returns when a write occurs– In: Timeout– Out: return code: error, interrupt, success, etc.

• counted_wait # local, return when number of writes is

# greater than the number of # counted waits– In: Timeout



Complex/Thread: LCO• Complex/Thread constructor

– In: Action– In: data, byte_array– In: receptor, byte_array # can be null– Optional In: contin1, (T) Thread, (TL)

Thread_list– Optional In: contin2, (G) GID, (GL) GID_list

• start– Optional Out: (R) RunningThread

• set_state• get_state



Complex

• send_and_exit– In: byte_array– In: Offset– In: Length– # This writes to all continuations

# and terminates the thread



Pseudo C Code

XPI_Action action;XPI_Thread thread, next1, next2;XPI_RunningThread run;XPI_GID gid;struct BH_data *bh_data;XPI_Buffer_init(sizeof(BH_data),XPI_RECEIVE,&bh_data);...XPI_Thread_init_T(&thread,&action,bh_data,&next);XPI_Thread_start_R(&thread,&run);XPI_Thread_getgid(&thread,&gid);....XPI_RunningThread_set_state(&run,XPI_TERMINATE);



Action: Portable Function Ref

• Action constructor– In: function_id, String– In: data_size, int– In: data_repacker, Action

• Name of function used to repackage bytes for use on possibly different architectures available on a machine. Potentially difficult to write, auto generated by XPIPP tool based in on interface definition language. Null used on machines with homogeneous architecture.



Memory Managment

• mem_alloc– In: size, int– In: flags, int

• RECEIVE: can be a target for RDMA– In: data_repacker, Action

• # special value: IMMOBILE• # special value: ARRAY_OF_INT• # rely on tools to generate repackers

– Out: ref, (P) byte_array, (G) GID



Memory Management• mem_free

– In: data, (P) byte_array, (G) GID• mem_getptr

– In: GID– Out: byte_array

• mem_getgid,– In: byte_array– out: GID

• Use this to unify disk and memory access as Jack Dennis suggests?



Pseudo C Code

// Data managed by XPIvoid init_data(void *intrinsic,void *recvd) {

struct BH_data *bh_data =(struct BH_data *)intrinsic;

... BH_event_horizon *eh;

XPI_Buffer_init(sizeof(eh),flags,&eh);XPI_send_and_exit(eh); // received by continuations

}XPI_Action action;XPI_Action_init(&action,"black_hole.init_data",10,NULL);



WorkQueue: LCO• WorkQueue constructor

– Out: id, (R) GID– In: receptor, byte_array

# WorkQueue runs one thread at a time. All threads share# the receptor as the second argument to the action

• add:– In: Complex/Thread # called if the GID is a parcel target



Parcels• Parcel constructor:

– In: Action– In: Data– In: destination, GID– Optional In: contin, (G) GID, (GL) GID_list

• start



Locality

• static Locality get_locality()– get_gid:

• Out: GID– get_property:

• In: name, String• Out: value, int



Process

• Process constructor– In: parent, GID– In: Locality_List

• set_policy: In: policy, In: param• get_policy: In: policy, Out: param• get_gid: Out: GID



Process• bind_symname

– In: sym_name, String # e.g. "console"– In: GID

• unbind_symname– In: sym_name, String

• get_main: static: Out: GID • get_parent: Out: GID, In: GID

– all GID's have a parent process!• get_current: static: Out: GID



Parcels

• Semantically similar to Thread• A better way to start a thread: Destination

can be a process, that starts a thread at the least loaded of the managed localities



Mobile Objects (AGAS)

• WorkQueue (easy)• Suspended Thread (difficult)

Just move work queues to start?

Documents

The XPI Interface