Changes between Version 1 and Version 2 of AppIntro

Timestamp:

Jun 9, 2008, 12:20:58 PM (16 years ago)

Author:

davea

Comment:

--

AppIntro

@@ -1 @@
-3) application structure options
-                runtime environment (disk)
-                simple/compound
-                wrapper
-                FORTRAN
-                Java, Python, Lisp
+= BOINC applications =
+
+BOINC lets you distribute pretty much any existing application program,
+written in any language.
+However, there are a few details you need to know.
+First, it's helpful to understand the environment in which
+BOINC executes applications.
+This has two aspects:
+
+'''Directory structure'''
+
+On a given volunteer host, each project has a separate '''project directory'''.
+All the files for that project - application files,
+input files, output files - are stored in the project directory.
+
+Each job runs in a separate '''slot directory''',
+which contains '''links''' to all the files needed by that job
+(these are like UNIX symbolic links; since Windows NTFS doesn't support
+symbolic links, BOINC implements them as XML files).
+The names of the link files are called '''logical names''',
+and the files they point to have '''physical names'''.
+
+The BOINC client expects each application to create a specially-named "finish file"
+when it is done; this lets it reliably detect when the application has finished
+(rather than, e.g., being killed).
+
+'''Control and communication'''
+
+The BOINC client interacts with running applications in two ways:
+
+ * The client tells the application when to suspend, resume, and quit.
+ * The application tells the client its current CPU time, and when it has checkpointed.
+
+This communication is implemented using a share-memory structure.
+There is a separate shared-memory structure for each running application.
+
+== The BOINC runtime library ==
+
+Suppose you tried to run an existing, unmodified program under BOINC.
+There would be two problems:
+
+ * When the program opens and reads its input files, it would get the contents of the XML link files - not what it expects.  Similarly, the output would be written to the wrong directory.
+ * When the program finishes, it wouldn't create a finish file, so the BOINC client would restart it repeatedly.
+ * The BOINC client wouldn't know the application's CPU time; it would display zero, and volunteers would be confused.
+
+The easiest way to solve these problems is to modify your program as follows:
+ * Add calls to BOINC initialization and finalization routines.
+ * Precede with fopen() call with a BOINC function that maps logical to physical names.
+ * Link it with the BOINC runtime library.
+
+== The BOINC wrapper ==
+
+Suppose you have a program that is difficult or impossible to modify
+to use the BOINC runtime library (e.g., source code is not available).
+You can run it under BOINC, using the '''BOINC wrapper'''.
+The wrapper acts as a main program,
+managing communication with the BOINC client,
+and running your program as a subprocess.
+
+== Language alternatives ==
+
+The BOINC runtime library is implemented in C++
+and is easiest to use from C/C++ programs.
+However, it also has a FORTRAN binding,
+and it is possible to run Java and Lisp programs under BOINC as well.