README.envvar

(C) 2010 by Argonne National Laboratory.
    See COPYRIGHT in top-level directory.

Automatically generated
  by:   ./maint/extractcvars
  at:   Thu Dec 18 11:29:56 2014
DO NOT EDIT!!!

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.
---------------------------------------------------------------------------

MPIR_CVAR_MEMDUMP
    Aliases: MPIR_PARAM_MEMDUMP
             MPICH_MEMDUMP
             MV2_MEMDUMP
    Description: If true, list any memory that was allocated by MPICH and
        that remains allocated when MPI_Finalize completes.
    Default: 1

MPIR_CVAR_ASYNC_PROGRESS
    Aliases: MPIR_PARAM_ASYNC_PROGRESS
             MPICH_ASYNC_PROGRESS
             MV2_ASYNC_PROGRESS
    Description: If set to true, MPICH will initiate an additional thread
        to make asynchronous progress on all communication operations
        including point-to-point, collective, one-sided operations and I/O.
         Setting this variable will automatically increase the
        thread-safety level to MPI_THREAD_MULTIPLE.  While this improves
        the progress semantics, it might cause a small amount of
        performance overhead for regular MPI operations.  The user is
        encouraged to leave one or more hardware threads vacant in order to
        prevent contention between the application threads and the progress
        thread(s).  The impact of oversubscription is highly system
        dependent but may be substantial in some cases, hence this
        recommendation.
    Default: 0

MPIR_CVAR_DEFAULT_THREAD_LEVEL
    Aliases: MPIR_PARAM_DEFAULT_THREAD_LEVEL
             MPICH_DEFAULT_THREAD_LEVEL
             MV2_DEFAULT_THREAD_LEVEL
    Description: Sets the default thread level to use when using MPI_INIT.
    Default: "MPI_THREAD_SINGLE"

MPIR_CVAR_DEBUG_HOLD
    Aliases: MPIR_PARAM_DEBUG_HOLD
             MPICH_DEBUG_HOLD
             MV2_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

MPIR_CVAR_ERROR_CHECKING
    Aliases: MPIR_PARAM_ERROR_CHECKING
             MPICH_ERROR_CHECKING
             MV2_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

MPIR_CVAR_SUPPRESS_ABORT_MESSAGE
    Aliases: MPIR_PARAM_SUPPRESS_ABORT_MESSAGE
             MPICH_SUPPRESS_ABORT_MESSAGE
             MV2_SUPPRESS_ABORT_MESSAGE
    Description: Disable printing of abort error message.
    Default: 0

MPIR_CVAR_PROCTABLE_SIZE
    Aliases: MPIR_PARAM_PROCTABLE_SIZE
             MPICH_PROCTABLE_SIZE
             MV2_PROCTABLE_SIZE
    Description: Size of the "MPIR" debugger interface proctable (process
        table).
    Default: 64

MPIR_CVAR_PROCTABLE_PRINT
    Aliases: MPIR_PARAM_PROCTABLE_PRINT
             MPICH_PROCTABLE_PRINT
             MV2_PROCTABLE_PRINT
    Description: If true, dump the proctable entries at
        MPIR_WaitForDebugger-time.
    Default: 0

MPIR_CVAR_SCATTER_INTER_SHORT_MSG_SIZE
    Aliases: MPIR_PARAM_SCATTER_INTER_SHORT_MSG_SIZE
             MPICH_SCATTER_INTER_SHORT_MSG_SIZE
             MV2_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

MPIR_CVAR_ENABLE_COLL_FT_RET
    Aliases: MPIR_PARAM_ENABLE_COLL_FT_RET
             MPICH_ENABLE_COLL_FT_RET
             MV2_ENABLE_COLL_FT_RET
    Description: DEPRECATED! Will be removed in MPICH-3.2 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: 1

MPIR_CVAR_ALLTOALL_SHORT_MSG_SIZE
    Aliases: MPIR_PARAM_ALLTOALL_SHORT_MSG_SIZE
             MPICH_ALLTOALL_SHORT_MSG_SIZE
             MV2_ALLTOALL_SHORT_MSG_SIZE
    Description: the short message algorithm will be used if the
        per-destination message size (sendcount*size(sendtype)) is <= this
        value (See also: MPIR_CVAR_ALLTOALL_MEDIUM_MSG_SIZE)
    Default: 256

MPIR_CVAR_ALLTOALL_MEDIUM_MSG_SIZE
    Aliases: MPIR_PARAM_ALLTOALL_MEDIUM_MSG_SIZE
             MPICH_ALLTOALL_MEDIUM_MSG_SIZE
             MV2_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 MPIR_CVAR_ALLTOALL_SHORT_MSG_SIZE (See also:
        MPIR_CVAR_ALLTOALL_SHORT_MSG_SIZE)
    Default: 32768

MPIR_CVAR_ALLTOALL_THROTTLE
    Aliases: MPIR_PARAM_ALLTOALL_THROTTLE
             MPICH_ALLTOALL_THROTTLE
             MV2_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: 32

MPIR_CVAR_GATHER_VSMALL_MSG_SIZE
    Aliases: MPIR_PARAM_GATHER_VSMALL_MSG_SIZE
             MPICH_GATHER_VSMALL_MSG_SIZE
             MV2_GATHER_VSMALL_MSG_SIZE
    Description: use a temporary buffer for intracommunicator MPI_Gather if
        the send buffer size is < this value (in bytes) (See also:
        MPIR_CVAR_GATHER_INTER_SHORT_MSG_SIZE)
    Default: 1024

MPIR_CVAR_GATHER_INTER_SHORT_MSG_SIZE
    Aliases: MPIR_PARAM_GATHER_INTER_SHORT_MSG_SIZE
             MPICH_GATHER_INTER_SHORT_MSG_SIZE
             MV2_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) (See
        also: MPIR_CVAR_GATHER_VSMALL_MSG_SIZE)
    Default: 2048

MPIR_CVAR_REDUCE_SHORT_MSG_SIZE
    Aliases: MPIR_PARAM_REDUCE_SHORT_MSG_SIZE
             MPICH_REDUCE_SHORT_MSG_SIZE
             MV2_REDUCE_SHORT_MSG_SIZE
    Description: the short message algorithm will be used if the send
        buffer size is <= this value (in bytes)
    Default: 2048

MPIR_CVAR_ENABLE_SMP_REDUCE
    Aliases: MPIR_PARAM_ENABLE_SMP_REDUCE
             MPICH_ENABLE_SMP_REDUCE
             MV2_ENABLE_SMP_REDUCE
    Description: Enable SMP aware reduce.
    Default: 1

MPIR_CVAR_MAX_SMP_REDUCE_MSG_SIZE
    Aliases: MPIR_PARAM_MAX_SMP_REDUCE_MSG_SIZE
             MPICH_MAX_SMP_REDUCE_MSG_SIZE
             MV2_MAX_SMP_REDUCE_MSG_SIZE
    Description: Maximum message size for which SMP-aware reduce is used. 
        A value of '0' uses SMP-aware reduce for all message sizes.
    Default: 0

MPIR_CVAR_ALLGATHER_SHORT_MSG_SIZE
    Aliases: MPIR_PARAM_ALLGATHER_SHORT_MSG_SIZE
             MPICH_ALLGATHER_SHORT_MSG_SIZE
             MV2_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). (See also: MPIR_CVAR_ALLGATHER_LONG_MSG_SIZE)
    Default: 81920

MPIR_CVAR_ALLGATHER_LONG_MSG_SIZE
    Aliases: MPIR_PARAM_ALLGATHER_LONG_MSG_SIZE
             MPICH_ALLGATHER_LONG_MSG_SIZE
             MV2_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) (See also: MPIR_CVAR_ALLGATHER_SHORT_MSG_SIZE)
    Default: 524288

MPIR_CVAR_BCAST_MIN_PROCS
    Aliases: MPIR_PARAM_BCAST_MIN_PROCS
             MPICH_BCAST_MIN_PROCS
             MV2_BCAST_MIN_PROCS
    Description: Let's define short messages as messages with size <
        MPIR_CVAR_BCAST_SHORT_MSG_SIZE, and medium messages as messages
        with size >= MPIR_CVAR_BCAST_SHORT_MSG_SIZE but <
        MPIR_CVAR_BCAST_LONG_MSG_SIZE, and long messages as messages with
        size >= MPIR_CVAR_BCAST_LONG_MSG_SIZE. The broadcast algorithms
        selection procedure is as follows. For short messages or when the
        number of processes is < MPIR_CVAR_BCAST_MIN_PROCS, we do broadcast
        using the binomial tree algorithm. Otherwise, for medium messages
        and with a power-of-two number of processes, we do broadcast based
        on a scatter followed by a recursive doubling allgather algorithm.
        Otherwise, for long messages or with non power-of-two number of
        processes, we do broadcast based on a scatter followed by a ring
        allgather algorithm. (See also: MPIR_CVAR_BCAST_SHORT_MSG_SIZE,
        MPIR_CVAR_BCAST_LONG_MSG_SIZE)
    Default: 8

MPIR_CVAR_BCAST_SHORT_MSG_SIZE
    Aliases: MPIR_PARAM_BCAST_SHORT_MSG_SIZE
             MPICH_BCAST_SHORT_MSG_SIZE
             MV2_BCAST_SHORT_MSG_SIZE
    Description: Let's define short messages as messages with size <
        MPIR_CVAR_BCAST_SHORT_MSG_SIZE, and medium messages as messages
        with size >= MPIR_CVAR_BCAST_SHORT_MSG_SIZE but <
        MPIR_CVAR_BCAST_LONG_MSG_SIZE, and long messages as messages with
        size >= MPIR_CVAR_BCAST_LONG_MSG_SIZE. The broadcast algorithms
        selection procedure is as follows. For short messages or when the
        number of processes is < MPIR_CVAR_BCAST_MIN_PROCS, we do broadcast
        using the binomial tree algorithm. Otherwise, for medium messages
        and with a power-of-two number of processes, we do broadcast based
        on a scatter followed by a recursive doubling allgather algorithm.
        Otherwise, for long messages or with non power-of-two number of
        processes, we do broadcast based on a scatter followed by a ring
        allgather algorithm. (See also: MPIR_CVAR_BCAST_MIN_PROCS,
        MPIR_CVAR_BCAST_LONG_MSG_SIZE)
    Default: 12288

MPIR_CVAR_BCAST_LONG_MSG_SIZE
    Aliases: MPIR_PARAM_BCAST_LONG_MSG_SIZE
             MPICH_BCAST_LONG_MSG_SIZE
             MV2_BCAST_LONG_MSG_SIZE
    Description: Let's define short messages as messages with size <
        MPIR_CVAR_BCAST_SHORT_MSG_SIZE, and medium messages as messages
        with size >= MPIR_CVAR_BCAST_SHORT_MSG_SIZE but <
        MPIR_CVAR_BCAST_LONG_MSG_SIZE, and long messages as messages with
        size >= MPIR_CVAR_BCAST_LONG_MSG_SIZE. The broadcast algorithms
        selection procedure is as follows. For short messages or when the
        number of processes is < MPIR_CVAR_BCAST_MIN_PROCS, we do broadcast
        using the binomial tree algorithm. Otherwise, for medium messages
        and with a power-of-two number of processes, we do broadcast based
        on a scatter followed by a recursive doubling allgather algorithm.
        Otherwise, for long messages or with non power-of-two number of
        processes, we do broadcast based on a scatter followed by a ring
        allgather algorithm. (See also: MPIR_CVAR_BCAST_MIN_PROCS,
        MPIR_CVAR_BCAST_SHORT_MSG_SIZE)
    Default: 524288

MPIR_CVAR_ENABLE_SMP_BCAST
    Aliases: MPIR_PARAM_ENABLE_SMP_BCAST
             MPICH_ENABLE_SMP_BCAST
             MV2_ENABLE_SMP_BCAST
    Description: Enable SMP aware broadcast (See also:
        MPIR_CVAR_MAX_SMP_BCAST_MSG_SIZE)
    Default: 1

MPIR_CVAR_MAX_SMP_BCAST_MSG_SIZE
    Aliases: MPIR_PARAM_MAX_SMP_BCAST_MSG_SIZE
             MPICH_MAX_SMP_BCAST_MSG_SIZE
             MV2_MAX_SMP_BCAST_MSG_SIZE
    Description: Maximum message size for which SMP-aware broadcast is
        used.  A value of '0' uses SMP-aware broadcast for all message
        sizes. (See also: MPIR_CVAR_ENABLE_SMP_BCAST)
    Default: 0

MPIR_CVAR_GATHERV_INTER_SSEND_MIN_PROCS
    Aliases: MPIR_PARAM_GATHERV_INTER_SSEND_MIN_PROCS
             MPICH_GATHERV_INTER_SSEND_MIN_PROCS
             MV2_GATHERV_INTER_SSEND_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

MPIR_CVAR_REDSCAT_COMMUTATIVE_LONG_MSG_SIZE
    Aliases: MPIR_PARAM_REDSCAT_COMMUTATIVE_LONG_MSG_SIZE
             MPICH_REDSCAT_COMMUTATIVE_LONG_MSG_SIZE
             MV2_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

MPIR_CVAR_ALLGATHERV_PIPELINE_MSG_SIZE
    Aliases: MPIR_PARAM_ALLGATHERV_PIPELINE_MSG_SIZE
             MPICH_ALLGATHERV_PIPELINE_MSG_SIZE
             MV2_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

MPIR_CVAR_ENABLE_SMP_BARRIER
    Aliases: MPIR_PARAM_ENABLE_SMP_BARRIER
             MPICH_ENABLE_SMP_BARRIER
             MV2_ENABLE_SMP_BARRIER
    Description: Enable SMP aware barrier.
    Default: 1

MPIR_CVAR_ALLREDUCE_SHORT_MSG_SIZE
    Aliases: MPIR_PARAM_ALLREDUCE_SHORT_MSG_SIZE
             MPICH_ALLREDUCE_SHORT_MSG_SIZE
             MV2_ALLREDUCE_SHORT_MSG_SIZE
    Description: the short message algorithm will be used if the send
        buffer size is <= this value (in bytes)
    Default: 2048

MPIR_CVAR_ENABLE_SMP_COLLECTIVES
    Aliases: MPIR_PARAM_ENABLE_SMP_COLLECTIVES
             MPICH_ENABLE_SMP_COLLECTIVES
             MV2_ENABLE_SMP_COLLECTIVES
    Description: Enable SMP aware collective communication.
    Default: 1

MPIR_CVAR_ENABLE_SMP_ALLREDUCE
    Aliases: MPIR_PARAM_ENABLE_SMP_ALLREDUCE
             MPICH_ENABLE_SMP_ALLREDUCE
             MV2_ENABLE_SMP_ALLREDUCE
    Description: Enable SMP aware allreduce.
    Default: 1

MPIR_CVAR_MAX_SMP_ALLREDUCE_MSG_SIZE
    Aliases: MPIR_PARAM_MAX_SMP_ALLREDUCE_MSG_SIZE
             MPICH_MAX_SMP_ALLREDUCE_MSG_SIZE
             MV2_MAX_SMP_ALLREDUCE_MSG_SIZE
    Description: Maximum message size for which SMP-aware allreduce is
        used.  A value of '0' uses SMP-aware allreduce for all message
        sizes.
    Default: 0

MPIR_CVAR_PRINT_ERROR_STACK
    Aliases: MPIR_PARAM_PRINT_ERROR_STACK
             MPICH_PRINT_ERROR_STACK
             MV2_PRINT_ERROR_STACK
    Description: If true, print an error stack trace at error handling
        time.
    Default: 1

MPIR_CVAR_CHOP_ERROR_STACK
    Aliases: MPIR_PARAM_CHOP_ERROR_STACK
             MPICH_CHOP_ERROR_STACK
             MV2_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

MPIR_CVAR_CTXID_EAGER_SIZE
    Aliases: MPIR_PARAM_CTXID_EAGER_SIZE
             MPICH_CTXID_EAGER_SIZE
             MV2_CTXID_EAGER_SIZE
    Description: The MPIR_CVAR_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

MPIR_CVAR_COMM_SPLIT_USE_QSORT
    Aliases: MPIR_PARAM_COMM_SPLIT_USE_QSORT
             MPICH_COMM_SPLIT_USE_QSORT
             MV2_COMM_SPLIT_USE_QSORT
    Description: Use qsort(3) in the implementation of MPI_Comm_split
        instead of bubble sort.
    Default: 1

MPIR_CVAR_NAMESERV_FILE_PUBDIR
    Aliases: MPIR_PARAM_NAMESERV_FILE_PUBDIR
             MPICH_NAMESERV_FILE_PUBDIR
             MV2_NAMESERV_FILE_PUBDIR
             MPIR_CVAR_NAMEPUB_DIR
             MPIR_PARAM_NAMEPUB_DIR
             MPICH_NAMEPUB_DIR
             MV2_NAMEPUB_DIR
    Description: Sets the directory to use for MPI service publishing in
        the file nameserv implementation.  Allows the user to override
        where the publish and lookup information is placed for
        connect/accept based applications.
    Default: NULL

MPIR_CVAR_ABORT_ON_LEAKED_HANDLES
    Aliases: MPIR_PARAM_ABORT_ON_LEAKED_HANDLES
             MPICH_ABORT_ON_LEAKED_HANDLES
             MV2_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

MPIR_CVAR_NEMESIS_POLLS_BEFORE_YIELD
    Aliases: MPIR_PARAM_NEMESIS_POLLS_BEFORE_YIELD
             MPICH_NEMESIS_POLLS_BEFORE_YIELD
             MV2_NEMESIS_POLLS_BEFORE_YIELD
    Description: When MPICH is in a busy waiting loop, it will periodically
        call a function to yield the processor.  This cvar sets the number
        of loops before the yield function is called.  A value of 0
        disables yielding.
    Default: 1000

MPIR_CVAR_COLL_ALIAS_CHECK
    Aliases: MPIR_PARAM_COLL_ALIAS_CHECK
             MPICH_COLL_ALIAS_CHECK
             MV2_COLL_ALIAS_CHECK
    Description: Enable checking of aliasing in collective operations
    Default: 1

MPIR_CVAR_CH3_ENABLE_HCOLL
    Aliases: MPIR_PARAM_CH3_ENABLE_HCOLL
             MPICH_CH3_ENABLE_HCOLL
             MV2_CH3_ENABLE_HCOLL
    Description: If true, enable HCOLL collectives.
    Default: 0

MPIR_CVAR_CH3_RMA_ACC_IMMED
    Aliases: MPIR_PARAM_CH3_RMA_ACC_IMMED
             MPICH_CH3_RMA_ACC_IMMED
             MV2_CH3_RMA_ACC_IMMED
    Description: Use the immediate accumulate optimization
    Default: 1

MPIR_CVAR_CH3_RMA_NREQUEST_THRESHOLD
    Aliases: MPIR_PARAM_CH3_RMA_NREQUEST_THRESHOLD
             MPICH_CH3_RMA_NREQUEST_THRESHOLD
             MV2_CH3_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

MPIR_CVAR_CH3_RMA_NREQUEST_NEW_THRESHOLD
    Aliases: MPIR_PARAM_CH3_RMA_NREQUEST_NEW_THRESHOLD
             MPICH_CH3_RMA_NREQUEST_NEW_THRESHOLD
             MV2_CH3_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: 0

MPIR_CVAR_CH3_RMA_GC_NUM_COMPLETED
    Aliases: MPIR_PARAM_CH3_RMA_GC_NUM_COMPLETED
             MPICH_CH3_RMA_GC_NUM_COMPLETED
             MV2_CH3_RMA_GC_NUM_COMPLETED
    Description: Threshold for the number of completed requests the runtime
        finds before it stops trying to find more completed requests in
        garbage collection function. Note that it works with
        MPIR_CVAR_CH3_RMA_GC_NUM_TESTED as an OR relation, which means
        runtime will stop checking when either one of its following
        conditions is satisfied or one of conditions of
        MPIR_CVAR_CH3_RMA_GC_NUM_TESTED is satisfied. When it is set to
        negative value, it means runtime will not stop checking the
        operation list until it reaches the end of the list. When it is set
        to positive value, it means runtime will not stop checking the
        operation list until it finds certain number of completed requests.
        When it is set to zero value, the outcome is undefined. Note that
        in garbage collection function, if runtime finds a chain of
        completed RMA requests, it will temporarily ignore this CVAR and
        try to find continuous completed requests as many as possible,
        until it meets an incomplete request.
    Default: (-1)

MPIR_CVAR_CH3_RMA_GC_NUM_TESTED
    Aliases: MPIR_PARAM_CH3_RMA_GC_NUM_TESTED
             MPICH_CH3_RMA_GC_NUM_TESTED
             MV2_CH3_RMA_GC_NUM_TESTED
    Description: Threshold for the number of RMA requests the runtime tests
        before it stops trying to check more requests in garbage collection
        routine. Note that it works with MPIR_CVAR_CH3_RMA_GC_NUM_COMPLETED
        as an OR relation, which means runtime will stop checking when
        either one of its following conditions is satisfied or one of
        conditions of MPIR_CVAR_CH3_RMA_GC_NUM_COMPLETED is satisfied. When
        it is set to negative value, runtime will not stop checking
        operation list until runtime reaches the end of the list. It has
        the risk of O(N) traversing overhead if there is no completed
        request in the list. When it is set to positive value, it means
        runtime will not stop checking the operation list until it visits
        such number of requests. Higher values may make more completed
        requests to be found, but it has the risk of visiting too many
        requests, leading to significant performance overhead. When it is
        set to zero value, runtime will stop checking the operation list
        immediately, which may cause weird performance in practice. Note
        that in garbage collection function, if runtime finds a chain of
        completed RMA requests, it will temporarily ignore this CVAR and
        try to find continuous completed requests as many as possible,
        until it meets an incomplete request.
    Default: 100

MPIR_CVAR_CH3_RMA_LOCK_IMMED
    Aliases: MPIR_PARAM_CH3_RMA_LOCK_IMMED
             MPICH_CH3_RMA_LOCK_IMMED
             MV2_CH3_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

MPIR_CVAR_CH3_RMA_MERGE_LOCK_OP_UNLOCK
    Aliases: MPIR_PARAM_CH3_RMA_MERGE_LOCK_OP_UNLOCK
             MPICH_CH3_RMA_MERGE_LOCK_OP_UNLOCK
             MV2_CH3_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

MPIR_CVAR_CH3_NOLOCAL
    Aliases: MPIR_PARAM_CH3_NOLOCAL
             MPICH_CH3_NOLOCAL
             MV2_CH3_NOLOCAL
             MPIR_CVAR_CH3_NO_LOCAL
             MPIR_PARAM_CH3_NO_LOCAL
             MPICH_CH3_NO_LOCAL
             MV2_CH3_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

MPIR_CVAR_CH3_ODD_EVEN_CLIQUES
    Aliases: MPIR_PARAM_CH3_ODD_EVEN_CLIQUES
             MPICH_CH3_ODD_EVEN_CLIQUES
             MV2_CH3_ODD_EVEN_CLIQUES
             MPIR_CVAR_CH3_EVEN_ODD_CLIQUES
             MPIR_PARAM_CH3_EVEN_ODD_CLIQUES
             MPICH_CH3_EVEN_ODD_CLIQUES
             MV2_CH3_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

MPIR_CVAR_CH3_EAGER_MAX_MSG_SIZE
    Aliases: MPIR_PARAM_CH3_EAGER_MAX_MSG_SIZE
             MPICH_CH3_EAGER_MAX_MSG_SIZE
             MV2_CH3_EAGER_MAX_MSG_SIZE
    Description: This cvar controls the message size at which CH3 switches
        from eager to rendezvous mode.
    Default: 131072

MPIR_CVAR_USE_BLOCKING
    Aliases: MPIR_PARAM_USE_BLOCKING
             MPICH_USE_BLOCKING
             MV2_USE_BLOCKING
    Description: Setting this parameter enables mvapich2 to use blocking
        mode progress. MPI applications do not take up any CPU when they
        are waiting for incoming messages.
    Default: 0

MPIR_CVAR_USE_SHARED_MEM
    Aliases: MPIR_PARAM_USE_SHARED_MEM
             MPICH_USE_SHARED_MEM
             MV2_USE_SHARED_MEM
    Description: Use shared memory for intra-node communication.
    Default: 1

MPIR_CVAR_ON_DEMAND_THRESHOLD
    Aliases: MPIR_PARAM_ON_DEMAND_THRESHOLD
             MPICH_ON_DEMAND_THRESHOLD
             MV2_ON_DEMAND_THRESHOLD
    Description: This defines threshold for enabling on-demand connection
        management scheme. When the size of the job is larger than the
        threshold value, on-demand connection management will be used.
    Default: 64

MPIR_CVAR_NEMESIS_MXM_BULK_CONNECT
    Aliases: MPIR_PARAM_NEMESIS_MXM_BULK_CONNECT
             MPICH_NEMESIS_MXM_BULK_CONNECT
             MV2_NEMESIS_MXM_BULK_CONNECT
    Description: If true, force mxm to connect all processes at
        initialization time.
    Default: 0

MPIR_CVAR_NEMESIS_MXM_BULK_DISCONNECT
    Aliases: MPIR_PARAM_NEMESIS_MXM_BULK_DISCONNECT
             MPICH_NEMESIS_MXM_BULK_DISCONNECT
             MV2_NEMESIS_MXM_BULK_DISCONNECT
    Description: If true, force mxm to disconnect all processes at
        finalization time.
    Default: 0

MPIR_CVAR_CH3_INTERFACE_HOSTNAME
    Aliases: MPIR_PARAM_CH3_INTERFACE_HOSTNAME
             MPICH_CH3_INTERFACE_HOSTNAME
             MV2_CH3_INTERFACE_HOSTNAME
             MPIR_CVAR_INTERFACE_HOSTNAME
             MPIR_PARAM_INTERFACE_HOSTNAME
             MPICH_INTERFACE_HOSTNAME
             MV2_INTERFACE_HOSTNAME
    Description: If non-NULL, this cvar specifies the IP address that other
        processes should use when connecting to this process. This cvar is
        mutually exclusive with the MPIR_CVAR_CH3_NETWORK_IFACE cvar and it
        is an error to set them both.
    Default: NULL

MPIR_CVAR_CH3_PORT_RANGE
    Aliases: MPIR_PARAM_CH3_PORT_RANGE
             MPICH_CH3_PORT_RANGE
             MV2_CH3_PORT_RANGE
             MPIR_CVAR_PORTRANGE
             MPIR_CVAR_PORT_RANGE
             MPIR_PARAM_PORTRANGE
             MPIR_PARAM_PORT_RANGE
             MPICH_PORTRANGE
             MPICH_PORT_RANGE
             MV2_PORTRANGE
             MV2_PORT_RANGE
    Description: The MPIR_CVAR_CH3_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>.  To specify any available port, use 0:0.
    Default: {0,0}

MPIR_CVAR_NEMESIS_TCP_NETWORK_IFACE
    Aliases: MPIR_PARAM_NEMESIS_TCP_NETWORK_IFACE
             MPICH_NEMESIS_TCP_NETWORK_IFACE
             MV2_NEMESIS_TCP_NETWORK_IFACE
             MPIR_CVAR_NETWORK_IFACE
             MPIR_PARAM_NETWORK_IFACE
             MPICH_NETWORK_IFACE
             MV2_NETWORK_IFACE
    Description: If non-NULL, this cvar specifies which pseudo-ethernet
        interface the tcp netmod should use (e.g., "eth1", "ib0"). Note,
        this is a Linux-specific cvar. This cvar is mutually exclusive with
        the MPIR_CVAR_CH3_INTERFACE_HOSTNAME cvar and it is an error to set
        them both.
    Default: NULL

MPIR_CVAR_NEMESIS_TCP_HOST_LOOKUP_RETRIES
    Aliases: MPIR_PARAM_NEMESIS_TCP_HOST_LOOKUP_RETRIES
             MPICH_NEMESIS_TCP_HOST_LOOKUP_RETRIES
             MV2_NEMESIS_TCP_HOST_LOOKUP_RETRIES
    Description: This cvar controls the number of times to retry the
        gethostbyname() function before giving up.
    Default: 10

MPIR_CVAR_NEMESIS_SHM_EAGER_MAX_SZ
    Aliases: MPIR_PARAM_NEMESIS_SHM_EAGER_MAX_SZ
             MPICH_NEMESIS_SHM_EAGER_MAX_SZ
             MV2_NEMESIS_SHM_EAGER_MAX_SZ
    Description: This cvar controls the message size at which Nemesis
        switches from eager to rendezvous mode for shared memory. If this
        cvar is set to -1, then Nemesis will choose an appropriate value.
    Default: -1

MPIR_CVAR_NEMESIS_SHM_READY_EAGER_MAX_SZ
    Aliases: MPIR_PARAM_NEMESIS_SHM_READY_EAGER_MAX_SZ
             MPICH_NEMESIS_SHM_READY_EAGER_MAX_SZ
             MV2_NEMESIS_SHM_READY_EAGER_MAX_SZ
    Description: This cvar controls the message size at which Nemesis
        switches from eager to rendezvous mode for ready-send messages.  If
        this cvar is set to -1, then ready messages will always be sent
        eagerly.  If this cvar is set to -2, then Nemesis will choose an
        appropriate value.
    Default: -2

MPIR_CVAR_NEMESIS_ENABLE_CKPOINT
    Aliases: MPIR_PARAM_NEMESIS_ENABLE_CKPOINT
             MPICH_NEMESIS_ENABLE_CKPOINT
             MV2_NEMESIS_ENABLE_CKPOINT
    Description: If true, enables checkpointing support and returns an
        error if checkpointing library cannot be initialized.
    Default: 0

MPIR_CVAR_NEMESIS_LMT_DMA_THRESHOLD
    Aliases: MPIR_PARAM_NEMESIS_LMT_DMA_THRESHOLD
             MPICH_NEMESIS_LMT_DMA_THRESHOLD
             MV2_NEMESIS_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

MPIR_CVAR_NEMESIS_NETMOD
    Aliases: MPIR_PARAM_NEMESIS_NETMOD
             MPICH_NEMESIS_NETMOD
             MV2_NEMESIS_NETMOD
    Description: If non-empty, this cvar specifies which network module
        should be used for communication.
    Default: ""