(C) 2011 by Argonne National Laboratory.
    See COPYRIGHT in top-level directory.

This file lists the various environment variables available to change the
behavior of the MPICH library.  These are intended to be used by advanced
users.
---------------------------------------------------------------------------

MPICH_ALLTOALL_SHORT_MSG_SIZE
    Aliases: MPIR_PARAM_ALLTOALL_SHORT_MSG_SIZE
    Description: the short message algorithm will be used if the
        per-destination message size (sendcount*size(sendtype)) is <= this
        value
    Default: 256

MPICH_ALLTOALL_MEDIUM_MSG_SIZE
    Aliases: MPIR_PARAM_ALLTOALL_MEDIUM_MSG_SIZE
    Description: the medium message algorithm will be used if the
        per-destination message size (sendcount*size(sendtype)) is <= this
        value and larger than ALLTOALL_SHORT_MSG_SIZE
    Default: 32768

MPICH_ALLTOALL_THROTTLE
    Aliases: MPIR_PARAM_ALLTOALL_THROTTLE
    Description: max no. of irecvs/isends posted at a time in some alltoall
        algorithms. Setting it to 0 causes all irecvs/isends to be posted
        at once.
    Default: 4

MPICH_REDSCAT_COMMUTATIVE_LONG_MSG_SIZE
    Aliases: MPIR_PARAM_REDSCAT_COMMUTATIVE_LONG_MSG_SIZE
    Description: the long message algorithm will be used if the operation
        is commutative and the send buffer size is >= this value (in bytes)
    Default: 524288

MPICH_BCAST_MIN_PROCS
    Aliases: MPIR_PARAM_BCAST_MIN_PROCS
    Description: the minimum number of processes in a communicator to use a
        non-binomial broadcast algorithm
    Default: 8

MPICH_BCAST_SHORT_MSG_SIZE
    Aliases: MPIR_PARAM_BCAST_SHORT_MSG_SIZE
    Description: the short message algorithm will be used if the send
        buffer size is < this value (in bytes)
    Default: 12288

MPICH_BCAST_LONG_MSG_SIZE
    Aliases: MPIR_PARAM_BCAST_LONG_MSG_SIZE
    Description: the long message algorithm will be used if the send buffer
        size is >= this value (in bytes)
    Default: 524288

MPICH_ALLGATHER_SHORT_MSG_SIZE
    Aliases: MPIR_PARAM_ALLGATHER_SHORT_MSG_SIZE
    Description: For MPI_Allgather and MPI_Allgatherv, the short message
        algorithm will be used if the send buffer size is < this value (in
        bytes).
    Default: 81920

MPICH_ALLGATHER_LONG_MSG_SIZE
    Aliases: MPIR_PARAM_ALLGATHER_LONG_MSG_SIZE
    Description: For MPI_Allgather and MPI_Allgatherv, the long message
        algorithm will be used if the send buffer size is >= this value (in
        bytes)
    Default: 524288

MPICH_REDUCE_SHORT_MSG_SIZE
    Aliases: MPIR_PARAM_REDUCE_SHORT_MSG_SIZE
    Description: the short message algorithm will be used if the send
        buffer size is <= this value (in bytes)
    Default: 2048

MPICH_ALLREDUCE_SHORT_MSG_SIZE
    Aliases: MPIR_PARAM_ALLREDUCE_SHORT_MSG_SIZE
    Description: the short message algorithm will be used if the send
        buffer size is <= this value (in bytes)
    Default: 2048

MPICH_GATHER_VSMALL_MSG_SIZE
    Aliases: MPIR_PARAM_GATHER_VSMALL_MSG_SIZE
    Description: use a temporary buffer for intracommunicator MPI_Gather if
        the send buffer size is < this value (in bytes)
    Default: 1024

MPICH_GATHER_INTER_SHORT_MSG_SIZE
    Aliases: MPIR_PARAM_GATHER_INTER_SHORT_MSG_SIZE
    Description: use the short message algorithm for intercommunicator
        MPI_Gather if the send buffer size is < this value (in bytes)
    Default: 2048

MPICH_GATHERV_INTER_SSEND_MIN_PROCS
    Aliases: MPIR_PARAM_GATHERV_INTER_SSEND_MIN_PROCS
             MPICH_GATHERV_MIN_PROCS
    Description: Use Ssend (synchronous send) for intercommunicator
        MPI_Gatherv if the "group B" size is >= this value.  Specifying
        "-1" always avoids using Ssend.  For backwards compatibility,
        specifying "0" uses the default value.
    Default: 32

MPICH_SCATTER_INTER_SHORT_MSG_SIZE
    Aliases: MPIR_PARAM_SCATTER_INTER_SHORT_MSG_SIZE
    Description: use the short message algorithm for intercommunicator
        MPI_Scatter if the send buffer size is < this value (in bytes)
    Default: 2048

MPICH_ALLGATHERV_PIPELINE_MSG_SIZE
    Aliases: MPIR_PARAM_ALLGATHERV_PIPELINE_MSG_SIZE
    Description: The smallest message size that will be used for the
        pipelined, large-message, ring algorithm in the MPI_Allgatherv
        implementation.
    Default: 32768

MPICH_COMM_SPLIT_USE_QSORT
    Aliases: MPIR_PARAM_COMM_SPLIT_USE_QSORT
    Description: Use qsort(3) in the implementation of MPI_Comm_split
        instead of bubble sort.
    Default: 1

MPICH_RMA_ACC_IMMED
    Aliases: MPIR_PARAM_RMA_ACC_IMMED
    Description: Use the immediate accumulate optimization
    Default: 1

MPICH_RMA_NREQUEST_THRESHOLD
    Aliases: MPIR_PARAM_RMA_NREQUEST_THRESHOLD
    Description: Threshold at which the RMA implementation attempts to
        complete requests while completing RMA operations and while using
        the lazy synchonization approach.  Change this value if programs
        fail because they run out of  requests or other internal resources
    Default: 4000

MPICH_RMA_NREQUEST_NEW_THRESHOLD
    Aliases: MPIR_PARAM_RMA_NREQUEST_NEW_THRESHOLD
    Description: Threshold for the number of new requests since the last
        attempt to complete pending requests.  Higher values can increase
        performance,  but may run the risk of exceeding the available
        number of requests or other internal resources.
    Default: 128

MPICH_RMA_LOCK_IMMED
    Aliases: MPIR_PARAM_RMA_LOCK_IMMED
    Description: Issue a request for the passive target RMA lock
        immediately.  Default behavior is to defer the lock request until
        the call to MPI_Win_unlock.
    Default: 0

MPICH_RMA_MERGE_LOCK_OP_UNLOCK
    Aliases: MPIR_PARAM_RMA_MERGE_LOCK_OP_UNLOCK
    Description: Enable/disable an optimization that merges lock, op, and
        unlock messages, for single-operation passive target epochs.
    Default: 1

MPICH_NOLOCAL
    Aliases: MPICH_NO_LOCAL
             MPIR_PARAM_NOLOCAL
             MPIR_PARAM_NO_LOCAL
    Description: If true, force all processes to operate as though all
        processes are located on another node.  For example, this disables
        shared memory communication hierarchical collectives.
    Default: 0

MPICH_ODD_EVEN_CLIQUES
    Aliases: MPICH_EVEN_ODD_CLIQUES
             MPIR_PARAM_ODD_EVEN_CLIQUES
             MPIR_PARAM_EVEN_ODD_CLIQUES
    Description: If true, odd procs on a node are seen as local to each
        other, and even procs on a node are seen as local to each other. 
        Used for debugging on a single machine.
    Default: 0

MPICH_POLLS_BEFORE_YIELD
    Aliases: MPIR_PARAM_POLLS_BEFORE_YIELD
    Description: When MPICH is in a busy waiting loop, it will periodically
        call a function to yield the processor.  This parameter sets the
        number of loops before the yield function is called.  A  value of 0
        disables yielding.
    Default: 1000

MPICH_MEMDUMP
    Aliases: MPIR_PARAM_MEMDUMP
    Description: If true, list any memory that was allocated by MPICH and
        that remains allocated when MPI_Finalize completes.
    Default: 1

MPICH_PROCTABLE_SIZE
    Aliases: MPIR_PARAM_PROCTABLE_SIZE
    Description: Size of the "MPIR" debugger interface proctable (process
        table).
    Default: 64

MPICH_PROCTABLE_PRINT
    Aliases: MPIR_PARAM_PROCTABLE_PRINT
    Description: If true, dump the proctable entries at
        MPIR_WaitForDebugger-time. (currently compile-time disabled by "#if
        0")
    Default: 1

MPICH_ERROR_CHECKING
    Aliases: MPIR_PARAM_ERROR_CHECKING
    Description: If true, perform checks for errors, typically to verify
        valid inputs to MPI routines.  Only effective when MPICH is
        configured with --enable-error-checking=runtime .
    Default: 1

MPICH_PRINT_ERROR_STACK
    Aliases: MPIR_PARAM_PRINT_ERROR_STACK
    Description: If true, print an error stack trace at error handling
        time.
    Default: 1

MPICH_CHOP_ERROR_STACK
    Aliases: MPIR_PARAM_CHOP_ERROR_STACK
    Description: If >0, truncate error stack output lines this many
        characters wide.  If 0, do not truncate, and if <0 use a sensible
        default.
    Default: 0

MPICH_NEM_LMT_DMA_THRESHOLD
    Aliases: MPIR_PARAM_NEM_LMT_DMA_THRESHOLD
    Description: Messages larger than this size will use the "dma" (knem)
        intranode LMT implementation, if it is enabled and available.
    Default: 2097152

MPICH_NEMESIS_NETMOD
    Aliases: MPIR_PARAM_NEMESIS_NETMOD
    Description: If non-empty, this parameter specifies which network
        module should be used for communication.
    Default: ""

MPICH_INTERFACE_HOSTNAME
    Aliases: MPIR_PARAM_INTERFACE_HOSTNAME
    Description: If non-NULL, this parameter specifies the IP address that
        other processes should use when connecting to this process. This
        parameter is mutually exclusive with the MPICH_NETWORK_IFACE
        parameter and it is an error to set them both.
    Default: NULL

MPICH_NETWORK_IFACE
    Aliases: MPIR_PARAM_NETWORK_IFACE
    Description: If non-NULL, this parameter specifies which
        pseudo-ethernet interface the tcp netmod should use (e.g., "eth1",
        "ib0").  Note, this is a Linux-specific parameter. This parameter
        is mutually exclusive with the MPICH_INTERFACE_HOSTNAME parameter
        and it is an error to set them both.
    Default: NULL

MPICH_HOST_LOOKUP_RETRIES
    Aliases: MPIR_PARAM_HOST_LOOKUP_RETRIES
    Description: This parameter controls the number of times to retry the 
        gethostbyname() function before giving up.
    Default: 10

MPICH_SHM_EAGER_MAX_SZ
    Aliases: MPIR_PARAM_SHM_EAGER_MAX_SZ
    Description: This parameter controls the message size at which Nemesis 
        switches from eager to rendezvous mode for shared memory. If this
        parameter is set to -1, then Nemesis will choose an appropriate
        value.
    Default: -1

MPICH_SHM_READY_EAGER_MAX_SZ
    Aliases: MPIR_PARAM_SHM_READY_EAGER_MAX_SZ
    Description: This parameter controls the message size at which Nemesis
        switches from eager to rendezvous mode for ready-send messages.  If
        this parameter is set to -1, then ready messages will always be
        sent eagerly.  If this parameter is set to -2, then Nemesis will
        choose an appropriate value.
    Default: -2

MPICH_COMM_OVERRIDES
    Aliases: MPIR_PARAM_COMM_OVERRIDES
    Description: If set to false, communication override functionality will
        be disabled for netmods that provide the override feature.  Some
        netmods may not honor this flag.
    Default: 1

MPICH_CH3_EAGER_MAX_MSG_SIZE
    Aliases: MPIR_PARAM_CH3_EAGER_MAX_MSG_SIZE
    Description: This parameter controls the message size at which CH3
        switches from eager to rendezvous mode.
    Default: 131072

MPICH_DEBUG_HOLD
    Aliases: MPIR_PARAM_DEBUG_HOLD
    Description: If true, causes processes to wait in MPI_Init and
        MPI_Initthread for a debugger to be attached.  Once the debugger
        has attached, the variable 'hold' should be set to 0 in order to
        allow the process to continue (e.g., in gdb, "set hold=0").
    Default: 0

MPICH_ENABLE_CKPOINT
    Aliases: MPIR_PARAM_ENABLE_CKPOINT
    Description: If true, enables checkpointing support and returns an
        error if checkpointing library cannot be initialized.
    Default: 0

MPICH_ENABLE_COLL_FT_RET
    Aliases: MPIR_PARAM_ENABLE_COLL_FT_RET
    Description: NOT COMPATIBLE WITH NONBLOCKING COLLECTIVES (see
        tt#1601)!!! Collectives called on a communicator with a failed
        process should not hang, however the result of the operation may be
        invalid even though the function returns MPI_SUCCESS.  This option
        enables an experimental feature that will return an error if the
        result of the collective is invalid.
    Default: 0

MPICH_ABORT_ON_LEAKED_HANDLES
    Aliases: MPIR_PARAM_ABORT_ON_LEAKED_HANDLES
    Description: If true, MPI will call MPI_Abort at MPI_Finalize if any
        MPI object handles have been leaked.  For example, if MPI_Comm_dup
        is called without calling a corresponding MPI_Comm_free.  For
        uninteresting reasons, enabling this option may prevent all known
        object leaks from being reported.  MPICH must have been configure
        with "--enable-g=handlealloc" or better in order for this
        functionality to work.
    Default: 0

MPICH_PORT_RANGE
    Aliases: MPICH_PORTRANGE
             MPIR_PARAM_PORT_RANGE
             MPIR_PARAM_PORTRANGE
    Description: The MPICH_PORT_RANGE environment variable allows you to
        specify the range of TCP ports to be used by the process manager
        and the MPICH library. The format of this variable is <low>:<high>.
    Default: {0,0}

MPICH_CTXID_EAGER_SIZE
    Aliases: MPIR_PARAM_CTXID_EAGER_SIZE
    Description: The MPICH_CTXID_EAGER_SIZE environment variable allows you
        to specify how many words in the context ID mask will be set aside
        for the eager allocation protocol.  If the application is running
        out of context IDs, reducing this value may help.
    Default: 2

---------------------------------------------------------------------------

Automatically generated
  by:   ./maint/genparams
  at:   Wed Apr 24 10:08:33 2013
  from: src/util/param/params.yml (md5sum 91c960f4c6f9b5a91b7c68ea79732d69)

