Ubuntu Manpage: XMPI - X Window MPI user interface

NAME

       XMPI - X Window MPI user interface

SYNTAX

       xmpi [-h] [<boot_schema>]

DESCRIPTION

       XMPI  is a graphical user interface for running MPI programs, monitoring MPI processes and
       messages, and viewing execution trace files.  It exploits the  debugging  capabilities  of
       LAM,  a  parallel  computing  environment for UNIX clusters.  XMPI is constructed from the
       Motif widget set.

       XMPI does not provide an interface for starting a LAM session.  This must be  accomplished
       prior  to running XMPI, which is itself a LAM program.  The boot schema from which LAM was
       started can (should) be provided to XMPI so that it may be presented as  an  inventory  of
       nodes  on  which programs may be run.  If XMPI is to be used only to view trace files then
       starting LAM is not required.

       This description assumes a basic knowledge of MPI.

TYPICAL USAGE

XMPI provides a graphical display of the state of the processes within an MPI application.
The state information is obtained from one of two sources, a running application started
by XMPI or a file containing trace data from a traced MPI application. When XMPI is
started, its top-level overview window is blank. Once an application is started or a
trace file is loaded the overview window fills with a tiled group of hexagons, each
representing the state of one MPI process and labeled by the process rank within
MPI_COMM_WORLD. A traffic light symbol indicates whether the process is running or
blocked. No traffic light is shown for processes which have either finalized or not yet
initialized the MPI library.

When monitoring a running application the camera "Snap" button or "Snapshot" item in the
"Application" menu updates the state information on all processes at any time. When
viewing trace data the state information is updated according to the currently selected
time point (see "XMPI TRACE FILES").

A mouse click inside a hexagon pops up an additional window containing more detailed
information about the process. If the process is blocked, the function name, peer process
rank, communicator, message tag and element count are displayed. If unreceived messages
are available, their quantity, source process rank, communicator, message tag and element
count are displayed. By leaving a few process windows on the screen, a user can focus
debugging on a small and manageable collection of misbehaving processes.

The "Clean" button or "Clean" item in the "Application" menu terminates an application and
the development cycle can be repeated. The previous application can be rerun with the
"Rerun" button or "Rerun" item in the "Application" menu.

RUNNING AN APPLICATION

An application schema specifies an MPI application by listing each process's program name,
program location, target processor(s) and optional command line arguments.

The "Browse&Run" item in the "Application" menu pops up a simple file browser for choosing
and running a pre-written application schema. Alternatively an application schema can be
configured with the XMPI application builder dialog, invoked by the "Build&Run" item in
the "Application" menu.

The builder dialog has an area to specify each process and an arrow button to add it to
the application schema, which is shown below the arrow button in a scrolled list. The
lines in the list show the syntax that would be used in creating the same application with
a text editor. Indeed, the "Save" button saves the application schema in a file for later
use and/or editing.

A specified process does not become part of the application until the arrow (commit)
button is pressed. Once it appears in the application scrolled list, a process can be
deleted by selecting it and pressing the <Delete> key.

Pressing the "Run" button with anything in the application list causes that application to
be run. The overview window is then initialized with the status of the application.

Program Specification
A file browser in the middle of the builder dialog aids in selecting a program file. The
browser only navigates the file space of the node running XMPI. If a program is located
on another node outside the file space (outside NFS, etc.) its pathname may need to be
typed into the process specification area. Selecting the "Use Full Pathname" toggle
button will cause programs to be placed into the application schema as full pathnames.

XMPI limits the choice of a program source node to either the node running XMPI or the
process target node. The latter case is the default and is the most efficient because LAM
does not need to transfer the program from source to target node. The "Transfer Program"
toggle button selects the source node policy.

Multiple Program Copies
The number of copies of a program to be run can be set in the process specification area.
Clicking on the increment or decrement arrow will increment or decrement the count by one.
Clicking with the shift key down will increment or decrement by ten.

Command-line Arguments
Command-line arguments must be typed into the process specification area.

Node Specification
A boot schema specifies the computers participating as nodes in a LAM multicomputer. If
XMPI is given a boot schema filename, its contents will appear in a scrolled list on the
right side of the builder dialog. XMPI will search for the given schema in the local
directory. The boot schema filename is displayed above the list of its nodes. Multiple
target nodes can be selected from the scrolled list with the corresponding node mnemonic
appearing in the process specification area. Selecting multiple target nodes specifies
multiple processes with the program name, arguments and source node policy held constant.

If no boot schema was specified only the special node selectors "LOCAL" (meaning the node
on which XMPI is running) and "ALL NODES" are provided.

Target node descriptions may also be typed directly into the process specification area.
The local node is specified as h. The origin node from which the machine was booted, if
not local, can be specified as o. All usable nodes are specified as N. Nodes are
generically identified as n<list>, where <list> can be a single node identifier or a list
of node identifiers. Identifiers can be written in decimal or hexadecimal notation.
Examples are n1 or n0-7,0x10.

Run-time Options
Applications can be run with various run-time options to specify the behaviour of the MPI
library. These can be configured from a separate dialog which is activated from the
"Runtime" item in the "Options" menu. Options remain in effect until changed.

• tracing mode (default enabled)

• fast client-to-client communication (default disabled)

• GER protocol and error detection (default enabled)

• homogeneous LAM node optimization (default disabled)

FOCUSING ON A PROCESS

More information on a process's state can be obtained by clicking the left mouse button
within the process hexagon. This will pop up a focus window. The upper area of the focus
window is the process area and displays the current state of the process. The lower area
is the message area and displays information on the process's message queue.

The focus window banner contains a tack button which can be clicked to dismiss the window
and a label containing the process's identity along with the program name. In XMPI
processes are identified first by their rank in MPI_COMM_WORLD and if the process is
communicating, with a slash followed by the process's rank within the current
communicator. The focus window can also be dismissed by clicking once again in the
process hexagon.

The process area describes the current state of the process together with the name of and
(where appropriate) arguments to the MPI function currently being executed. The layout is
fairly self-explanatory and we describe only the less obvious features.

Communicator Identification
The "comm" area shows the communicator being used in the current MPI function.
Communicators are opaque objects which MPI does not identify in any meaningful, printable
way. LAM's MPI implementation adds a simple numerical identifier to communicators, which
is displayed in XMPI as <x> where x is the identifier. This identifier can be matched to
communicator variables in an MPI program with the LAM function, MPIL_Comm_id(2).

Group Membership
The button to the right of the "comm" area will highlight in the overview window the
hexagons of the processes in the communicator. For an intracommunicator, the hexagons
will be highlighted in the color specified by the "lcomCol" resource. For an
intercommunicator, processes in the local group will be highlighted in the color specified
by the "lcomCol" resource and those in the remote group in the color specified by the
"rcomCol" resource. For highlighted processes the process identification at the bottom of
the hexagon is changed to be the rank in MPI_COMM_WORLD followed by a slash and the rank
in the communicator being highlighted.

Datatype
The datatype button to the right of the "cnt" area will display in the datatype window
(see "DATATYPE WINDOW") the type map of the datatype argument to the current MPI function.

The message area describes the current state of the queue of messages destined to the
process and not yet received. Once again the layout is fairly self-explanatory and we
describe only the less obvious features.

Message Aggregates
Identical undelivered messages are aggregated. The "copy" area shows the number of
messages within the visible aggregate, followed by the total number of messages in the
queue. The button to the right of the "copy" area cycles through the message aggregates.

Source Rank
The "src" area shows the rank of the source process within MPI_COMM_WORLD followed by the
rank of the source process in the communicator in which the message was sent.

Datatype
The datatype button to the right of the "cnt" area will display in the datatype window the
type map of the message's datatype.

Group Membership
The button to the right of the "comm" area will highlight the message communicator in the
manner previously described.

XMPI TRACE FILES

       XMPI  can  be  used to view existing trace files and can be used to create trace files for
       applications run under XMPI.

       To load and view an existing trace file select the "View" item in the "Trace" menu.

       If an application is run under XMPI with tracing enabled (the default), LAM will trace the
       application.   Before  the  trace  data can be viewed in XMPI it must be dumped to a file.
       This is done by selecting the "Dump" item from the "Trace" menu.  You will be prompted for
       a  file  name.  By convention XMPI trace files have a ".lamtr" suffix.  The trace file can
       be viewed by loading it as described above.  As a shortcut select the  "Express"  item  in
       the  "Trace"  menu, or equivalently click the "Trace" button in the overview window.  This
       dumps the trace data to a temporary file and then immediately loads the file for  viewing.
       If  you  decide  that  you want to save trace data for later viewing then you must dump it
       using the "Dump" item from the "Trace" menu.  Dumping trace data to file  does  not  purge
       any trace data and a subsequent dump will contain all the trace data from the start of the
       application up until the time of dumping.  Terminating  an  application  via  the  "Clean"
       button or menu item purges all trace data.

       While  viewing  a trace an application previously launched by XMPI continues to run in the
       background.  Upon the closing of the trace window XMPI will return  to  snapshot  mode  if
       there is a running application.

       When   loading   trace  files  containing  multiple  segments  (see  MPIL_Trace_on(2)  and
       MPIL_Trace_off(2)) you will be prompted for the number of the segment you  wish  to  view.
       If  you  wish  later to view a different segment, simply reload the trace file and specify
       the new segment number when prompted.  Reloading is done via the "View" or "Express" items
       in the "Trace" menu.

   Communication Timeline Window
       Across  the  top of the timeline window is a control and information area.  The trace data
       is displayed below this on timelines, one per process  in  the  traced  application.   The
       state  of the application at a particular time is represented by the corresponding traffic
       light color.  Green represents running, red represents blocked  waiting  on  communication
       and  yellow  represents time spent inside an MPI function not blocked on communication (we
       call this system overhead time as it typically  represents  time  doing  data  conversion,
       message packing, etc).

       The  dial  can  be  used  to  select  a  time  point at which the process states are to be
       displayed.  In the overview window the process states at the dial time  are  displayed  in
       hexagon  form.   As  with  snapshot  mode  more  detailed  information on a process can be
       obtained by bringing up its focus window.  The dial may be moved by clicking with the left
       button  in  the  trace  view  area  or  via  the VCR controls.  Below the VCR controls are
       displayed from left to right, the time of the left edge of  the  displayed  timeline,  the
       current dial time and the time of the right edge of the displayed timeline.

       To  the  right  of  the VCR controls is displayed the current magnification.  When a trace
       file is loaded XMPI chooses an initial  scaling  factor  and  sets  this  to  be  the  1x1
       magnification.  You can increase and decrease the magnification using the zoom and un-zoom
       buttons.

       A segment of the currently displayed timeline can be selected by dragging the right  mouse
       button  in  the  timeline  display  area.  Upon release of the right button the display is
       zoomed to show the selected segment.  To cancel a drag in progress, drag the cursor up  or
       down out of the timeline display area.

   How Communication Is Represented
       Collective
           A collective communication is represented for each process by contiguous line segments
           showing the time spent in system overhead and  the  time  spent  blocked  waiting  for
           communication.   No  lines  are  drawn  connecting  the processes participating in the
           collective communication.

       Blocking_point_to_point
           For both the send and receive process contiguous line segments are drawn  showing  the
           time spent in system overhead and the time spent blocked waiting for the communication
           to complete.  A line is drawn connecting the send to the receive.   It  originates  at
           the  beginning  of  the  send segments and is drawn to the end of the matching receive
           segments.

       Non-blocking_point_to_point
           At the time a non-blocking send or receive is initiated a system overhead  segment  is
           drawn.   When  the  communication  is  completed  via a wait or test, segments showing
           system overhead and blocking time are drawn.  Lines are drawn between  matching  sends
           and  receives,  except  in this case the line is drawn from the segment where the send
           was initiated to where the corresponding receive completed.

       Waits_and_tests
           If a non-blocking communication is completed inside a  wait/test  function  XMPI  will
           show  the  function  name  in  the  focus window as the wait/test function followed in
           parentheses by  the  send/receive  function  being  completed.   For  example,  if  an
           MPI_Issend()  is  completed  inside  an  MPI_Wait(),  the  function will read MPI_Wait
           (MPI_Issend).

       Missing_traces
           Owing to  the  use  of  trace  segments  or  the  dropping  of  overflow  traces  (see
           lamtrace(1))  there  may  be  send  or receive traces which have no match in the trace
           data.  In these cases a short stub line is drawn out from a send or in to a receive.

   Kiviat Window
       When viewing a trace file,  the "Kiviat" button or "Kiviat" item  from  the  "Trace"  menu
       brings  up  the Kiviat window.  This window displays, in a segmented pie-chart format, the
       cumulative time up to the current dial  time,  spent  by  each  process  in  the  running,
       overhead and blocked states.

MESSAGE SOURCE MATRIX

       The  message source window displays a square matrix of process message queue lengths.  For
       each process it shows the number of  queued  messages  from  each  other  process  in  the
       application.  It can be brought up while monitoring a running application or while viewing
       a trace file, by selecting the "Matrix" button or "Matrix" item in the "Trace" menu.

DATATYPE WINDOW

       The datatype window displays a textual representation of the type map of an MPI  datatype.
       This  window  is  associated  at  any  instant  with  a  particular process and mode.  The
       associated process is shown in the window's banner and the mode is indicated by a  traffic
       light  or  message  queue icon shown in the left part of the window.  When in process mode
       the datatype being shown, if any, is the datatype argument of the MPI function the process
       is  executing.  When in message mode the datatype is that of the current message aggregate
       selected in the process focus window.  Switching between processes and modes  is  effected
       via the datatype buttons in the process focus windows.

       The  type  map  might  not fit completely into the default size window.  Simply resize the
       window to see the whole map.

SWITCHING INFORMATION SOURCES

       XMPI will gather and display information from either the currently  executing  application
       or a trace file.  When an application is launched from XMPI, the information source is the
       executing application and the "Snap" button is active.   Though  the  application  may  be
       producing  trace data, the "Snap" button does not use it, but instead acquires information
       from debugging hooks in the MPI implementation.  At any moment, an existing trace file may
       be  loaded  into XMPI or the currently accumulating trace data may be fetched from the MPI
       implementation, stored in a file, and loaded.  This action changes the information  source
       to  the  loaded  trace  file.   Information display is now controlled from the dial in the
       timeline window and not from the  "Snap"  button,  which  is  now  inactive.   Though  the
       application  may  still  be  running, the timeline dial does not use the runtime debugging
       hooks, but instead acquires information from the loaded trace file.  Upon the  closing  of
       the trace window XMPI will return to snapshot mode if there is a running application.

RESOURCES

       XMPI defines the following application resources.

       XMPI.helpCmd        command  that  is  run  to  provide  help.  The default is typically a
                           command which fires up a Web browser to view a help page.  You  should
                           change this to invoke your favourite browser.

       XMPI.rankFont       process rank font in hexagon

       XMPI.msgFont        total  message  count  font in hexagon (may need to be adjusted to fit
                           inside message icon)

       XMPI.lcomCol        color used to highlight the processes in an  intracommunicator  or  in
                           the the local group of an intercommunicator

       XMPI.rcomCol        color  used  to  highlight  the  processes  in  the remote group of an
                           intercommunicator

       XMPI.bandCol        color used for the zoom selection rubber band

       XMPI.bandDash       if True use a dashed line rubber  band  to  show  the  zoom  selection
                           otherwise use a solid line

       XMPI.bandWidth      width of the zoom selection rubber band

       XMPI  gets  important default resources from the application defaults file, XMPI.  If this
       file is not installed in the X11 default directory, its directory  can  be  added  to  the
       XAPPLRESDIR environment variable.

LIMITATIONS

       An application must be started by XMPI to be monitored by it.

       When  using  the  fast client-to-client communication mode process states in snapshot mode
       are always shown as running and no useful  information  is  shown  in  the  process  focus
       windows.

       XMPI  uses lamclean(1).  Errors reported by this tool will still print to standard output.
       A shorter message will appear in an XMPI error dialog.