1. Go4 CHEP 2001 Multithreaded Inter-Task Communication with ROOT -
GSI Online Offline Object Oriented
Go4
Multithreaded Inter-Task Communication with ROOT -
writing non-blocking GUIs
J. Adamczewski, M. Al-Turany, D. Bertini, H.G.Essel
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2. Contents Go4: Software layers and architecture Go4 Requirements
Multithreading (threadmanager library)
Inter task communication (taskhandler library)
Example: GUI task and analysis task
GUI implemetation with ROOT-Qt Interface
Demo (movie)
Summary
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3. ROOT Framework Go4 Package Layers Go4 Event Analysis Loop (Client)
Go4 GUI (Server)
Go4TaskHandler
Qt Library
Go4ThreadManager
Interface
TThread
ROOT Framework
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4. On-line Analysis with non blocking GUI
Requirements of Go4
On-line Analysis with non blocking GUI
Analysis based on ROOT
Analysis runs permanently
Analysis updates graphics asynchronously
GUI is never blocked
GUI controls and steers analysis
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5. Threadmanager library
Problems to solve
Multithreading necessary
ROOT classes not inherently thread save
 lock object creation and ROOT services
 nonblocking GUI and analysis: different tasks
Communication between tasks
Threadmanager library
Taskhandler library
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6. Go4 Multitasking system
Only one working thread per task (object creation, memory allocation, ROOT system calls)
Analysis and GUI in separate tasks (non blocking GUI, continuous analysis)
Communication:
raw socket transport (dedicated threads with TBuffer fields in TGo4Socket)
Object streaming by ROOT (working thread uses TGo4Queue methods)
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7. Functional overview GUI Data Loop Display Task (Server)
Drawing Thread
Logging Thread
Useraction
queue
queue
queue
Launch Thread
Task Handler
Command Thread
Data Thread
Status Thread
Connector Thread
IP Network
Data Loop
Command Thread
Data Thread
Status Thread
Task Handler
Two tasks with each including threads and communicating via a transport implementation
Display:
GUI and X timer (for repeated requests, refresh) run in the main root gApplication loop; GUI callbacks send commands to analysis; Objects (e.g. histograms) are received from analysis by update thread; logger thread receives status information.
Both threads and GUI share access to same graphics (Canvas, Listbox, Buttons..)
Analysis:
Event Loop runs as thread, same thread also executes dynamic commands (like histogram requests) and macros;
Status thread sends current analysis state;
Controlled from Display by Command thread: queues commands to Event Loop; may cancel/restart eventloop thread in case of latchup; controls a timer notify waiting for TCondition, which blocks the main root gApplication loop, since this showed to affect the thread stability (no TThread::Lock in TApplication). When root system loop is needed (thread restart, macro), block timer notify is released; next time it is blocked by condition wait again. => threadsave TApplication.Run in future?
queue
queue
queue
Analysis Tasks (Client 1,2,...)
Work Thread
Watcher Thread
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8.  Go4 GUI Complex GUI Qt graphics library Rapid prototyping
professional, powerful, free,
tools (QtDesigner), well documented 
Use ROOT and Qt together! no changes to ROOT sources
Go4 GUI architecture:
signal-slot mechanism (both Qt and ROOT)
gui singleton: registry + dispatcher (modified mediator pattern)
persistent status objects per window
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9. Go4 GUI: Qt-ROOT interface
QApplication
TApplication
QROOTApplication
TQApplication
Qt Eventloop
QApplication::Exec()
QTimer
ROOT Eventloop
TSystem::InnerLoop()
TTimer
TThread
QWidget
QWidget
TSocket
other...
TQROOTCanvas
QWidget
TCanvas
TRootGuiFactory
TQRootGuiFactory
TCanvasImp
TQCanvasImp
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10. Go4 GUI: Qt-ROOT interface
Follows the general ROOT GUI ABC
no changes in ROOT source necessary
Inheritance from ROOT base classes
TQRootGuiFactory (TRootGuiFactory)
Qt Factory GUI components
TQCanvasImp (TCanvasImp)
creates a Qt independent main window (QMainWindow)
sets TQRootCanvas as a central widget
TQApplication (TApplication)
ROOT environment set with a Qt GUI factory
Inheritance from Qt base class
QRootApplication (QApplication)
enable Qt evt-loop to drive Qt based GUI applications
call ROOT inner loop repeatedly to enable ROOT system events
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11. Qt Designer screenshot
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12. Using Qt designer
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13. Go4 GUI design GUISingleton registry Display command dispatcher
status mediator
commands
Display
taskhandler server IP
data
to analysis
register
(dependency)
update
Qt GUI
Widgets
Status
Slots
Qt GUI
Widgets
Status
Slots
Root GUI
Widgets
Status
Slots
Qt GUI
Widgets
Status
Slots
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14. ready to use for any ROOT application
Summary
Go4 thread manager package
Go4 task handler package
Go4 Qt-ROOT interface
ready to use for any ROOT application
Client task could be analysis framework, slow ctrl,...
GUI task can use Qt graphics library
Go4 analysis framework and GUI is being under development...
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15. Go4 demo monitored histograms ROOT canvas Control panel analysis
status
Here comes the sun ...
local
objects
remote
objects
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16. Go4 demo Initializing a remote analysis
Control of analysis: run status, list object folders
Monitor remote histograms continuously
Get and update local object copies
Working on local histograms (fit panel, save)
ROOT TBrowser works in parallel
Go4 Browser plots: superimpose, multiwindow
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17. Go4 demo
Here comes the sun ...
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18. Go4 demo
Here comes the sun ...
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19. Go4 demo
Here comes the sun ...
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20. Go4 demo
Here comes the sun ...
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21. Go4 demo regular ROOT TBrowser, works together with Qt 04.09.01
Here comes the sun ...
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22. Go4 demo
Here comes the sun ...
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