Changes between Version 15 and Version 16 of AppMultiThread

Timestamp:

Mar 12, 2008, 4:25:04 PM (16 years ago)

Author:

davea

Comment:

--

AppMultiThread

@@ -19 +19 @@
 or libraries of multi-threaded numerical "kernels".
 
-== Assumptions ==
+== Deploying a multi-threaded app version ==
 
-We assume that an app version has a parameter Nthreads,
-the maximum number of threads it uses.
-The scheduler sends a host the app version for which Nthreads <= NCPUS and is greatest.
+BOINC uses the [AppPlan application planning] mechanism to
+coordinate the scheduling of multi-threaded applications.
 
-== Scheduling policy ==
+Suppose you've developed a multi-threaded program,
+and that it achieves a linear speedup on up to 16 processors, and no additional speedup beyond that.
+To deploy it:
+
+ * Choose a "planning class" name for the program, say "par16" (see below).
+ * Create an [UpdateVersions app version].  Include a file '''app_plan''' containing "par16".
+ * Link the following function into your scheduler:
+{{{
+bool app_plan(HOST& host, char* plan_class, HOST_USAGE& hu) {
+    if (!strcmp(plan_class, "par16")) {
+        if (host.ncpus < 16) {
+            hu.ncpus = host.ncpus;
+            hu.flops = host.p_fpops*host.p_ncpus;
+        } else {
+            hu.ncpus = 16;
+            hu.flops = host.p_fpops*16;
+        }
+        return true;
+    }
+    return false;
+}
+}}}
+
+== Client scheduling policy ==
 
 Suppose an app A uses NT(A) threads.
@@ -40 +62 @@
  * Given a set of runnable applications A1, A2 (ordered by priority or deadline), run applications until the number of actual threads exceeds N.
 
-== API ==
+== Notes ==
 
-API functions:
-{{{
-int boinc_ncpus_available();
-}}}
-This returns the number of available CPUs
-(this may be less than the number of physical CPUs,
-if the user preferences specify this).
-An application should call {{{boinc_ncpus_available()}}} on startup
-to decide how many threads to use.
-It may optionally call it again at points where it is able to change its number of threads,
-in case the number of available CPUs has changed
-(e.g. as the computer becomes idle and busy).
-{{{
-void boinc_nthreads(int actual);
-}}}
-An application calls this to report its actual number of threads.
-It should call this whenever this quantity changes.
-
-A WU DB record can specify "max average threads",
-an estimate of the average number of threads on a host with arbitrarily many CPUs.
-This is used by the client and scheduler to estimate completion time.
-
-== Implementation ==
-
-App init file:
- * <ncpus_available>
-
-State:
- * int ACTIVE_TASK::nthreads
-
-Implementation ({{{enforce_schedule()}}}):
-as we schedule jobs, decrement CPU count by {{{atp->nthreads}}}.
-{{{rr_simulation()}}} needs to be modified too.
-
-== Notes ==
  * The average number of CPUs used by an app may be less than its number of thread (because of I/O or synchronization).  Ideally the client should the number of CPUs, not the number of threads.
- * Applications can use more threads than available processors.  Thus, user preferences that limit the number of available processors may not be respected.