Changes between Version 42 and Version 43 of Public/User_Guide/OmpSs-2

Timestamp:

Jun 14, 2019, 5:31:09 PM (5 years ago)

Author:

Pedro Martinez-Ferror

Comment:

—

Public/User_Guide/OmpSs-2

@@ -262 +262 @@
 == Override the Number of Threads Used ==
 
-Let's have a closer look at the third implementation ''03.multisaxpy_task'' which took 0.648536 seconds to finish using 48 threads.
-
-A full CM node features 48 threads (0-47) divided in two sockets: 0-11,24-35 for the first socket and 12-23,36-47 for the second socket.  **Notice that they are indeed not consecutive! **
+Let's have a closer look at the third implementation, i.e. ''03.multisaxpy_task'', which took 0.648536 seconds to finish using 48 threads. Remember that a full CM node features 48 threads (0-47) divided in two sockets: 0-11,24-35 for the first socket and 12-23,36-47 for the second socket.  **Notice that they are indeed not consecutive! **
 
 We can change the threads used by !OmpSs-2 with the Linux command `taskset`.  For example, the command to run this binary with 24 threads interleaved between the two sockets would be:
@@ -282 +280 @@
 `taskset -c 0-5,12-17 ./03.multisaxpy_task 16777216 8192 100`
 
-Changing the number of threads assigned to !OmpSs-2 affects the performance of the application:
+Changing the number of threads assigned to !OmpSs-2 affects the performance of the application and not necessarily in a negative way, e.g. see below:
 {{{
 $ ./03.multisaxpy_task 16777216 8192 100
@@ -296 +294 @@
 }}}
 
+== Creating a Dependency Graph ==
+
+Let's continue with the same example used above and create a dependency graph using only 12 threads of one socket (e.g. the second), which demonstrated to be the affinity giving the best results. Furthermore, we are not longer interested in running 100 iterations (nor using a large number of elements) to benchmark this example and hence only one iteration will suffice to generate a complete graph of this application. Run the following command:
+
+`NANOS6=graph taskset -c 12-23 ./03.multisaxpy_task 196608 8192 1`
+
+This command can take some time.  Once it has finished it should have created a script with the name ''graph-XXXXX-YYYYYYYYY-script.sh'' and a directory ''graph-XXXXX-YYYYYYYYY-components''.  Execute the script by typing:
+
+`bash graph-XXXXX-YYYYYYYYY-script.sh`
+
+to merge the intermediate results into a single PDF file which should look like this:
+
+[[Image(SAXPYgraph.png, 30%)]]
+
+which illustrates 24 tasks executed in parallel using 12 threads.