int main(int argc, char *argv[]) {
simgrid::s4u::Engine e(&argc, argv);
- e->set_config("Item:Value");
+ e.set_config("Item:Value");
// Rest of your code
}
- **contexts/factory:** :ref:`cfg=contexts/factory`
- **contexts/guard-size:** :ref:`cfg=contexts/guard-size`
- **contexts/nthreads:** :ref:`cfg=contexts/nthreads`
-- **contexts/parallel-threshold:** :ref:`cfg=contexts/parallel-threshold`
- **contexts/stack-size:** :ref:`cfg=contexts/stack-size`
- **contexts/synchro:** :ref:`cfg=contexts/synchro`
- **network/bandwidth-factor:** :ref:`cfg=network/bandwidth-factor`
- **network/crosstraffic:** :ref:`cfg=network/crosstraffic`
- **network/latency-factor:** :ref:`cfg=network/latency-factor`
+- **network/loopback-lat:** :ref:`cfg=network/loopback`
+- **network/loopback-bw:** :ref:`cfg=network/loopback`
- **network/maxmin-selective-update:** :ref:`Network Optimization Level <options_model_optim>`
- **network/model:** :ref:`options_model_select`
- **network/optim:** :ref:`Network Optimization Level <options_model_optim>`
- ``cpu/model``: specify the used CPU model. We have only one model
for now:
- - **Cas01:** Simplistic CPU model (time=size/power)
+ - **Cas01:** Simplistic CPU model (time=size/speed)
- ``host/model``: The host concept is the aggregation of a CPU with a
network card. Three models exists, but actually, only 2 of them are
Note that with the default host model this option is activated by default.
+.. _cfg=network/loopback:
+
+Configuring loopback link
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Several network model provide an implicit loopback link to account for local
+communication on a host. By default it has a 10GBps bandwidth and a null latency.
+This can be changed with ``network/loopback-lat`` and ``network/loopback-bw``
+items.
+
.. _cfg=smpi/async-small-thresh:
Simulating Asynchronous Send
(this configuration item is experimental and may change or disappear)
-It is possible to specify that messages below a certain size will be
+It is possible to specify that messages below a certain size (in bytes) will be
sent as soon as the call to MPI_Send is issued, without waiting for
the correspondant receive. This threshold can be configured through
the ``smpi/async-small-thresh`` item. The default value is 0. This
- if (:ref:`smpi/send-is-detached-thresh <cfg=smpi/send-is-detached-thresh>` < size) then
MPI_Send returns only when the message has actually been sent over the network. This is known as the rendez-vous mode.
-The ``smpi/buffering`` option gives an easier interface to choose between these semantics. It can take two values:
+The ``smpi/buffering`` (only valid with MC) option gives an easier interface to choose between these semantics. It can take two values:
-- **zero:** means that buffering should be disabled. Blocking communications are actually blocking.
-- **infty:** means that buffering should be made infinite. Blocking communications are non-blocking.
+- **zero:** means that buffering should be disabled. All communications are actually blocking.
+- **infty:** means that buffering should be made infinite. All communications are non-blocking.
.. _cfg=model-check/property:
If you want to push the scalability limits of your code, you might
want to reduce the ``contexts/stack-size`` item. Its default value is
8192 (in KiB), while our Chord simulation works with stacks as small
-as 16 KiB, for example. This *setting is ignored* when using the
-thread factory. Instead, you should compile SimGrid and your
-application with ``-fsplit-stack``. Note that this compilation flag is
-not compatible with the model checker right now.
+as 16 KiB, for example. You can ensure that some actors have a specific
+size by simply changing the value of this configuration item before
+creating these actors. The :cpp:func:`simgrid::s4u::Engine::set_config`
+functions are handy for that.
+
+This *setting is ignored* when using the thread factory (because there
+is no way to modify the stack size with C++ system threads). Instead,
+you should compile SimGrid and your application with
+``-fsplit-stack``. Note that this compilation flag is not compatible
+with the model checker right now.
The operating system should only allocate memory for the pages of the
stack which are actually used and you might not need to use this in
application.
.. _cfg=contexts/nthreads:
-.. _cfg=contexts/parallel-threshold:
.. _cfg=contexts/synchro:
Running User Code in Parallel
of cores that you have in your computer (or lower than 1 to have the
amount of cores auto-detected).
-Even if you asked several worker threads using the previous option,
-you can request to start the parallel execution (and pay the
-associated synchronization costs) only if the potential parallelism is
-large enough. For that, set the ``contexts/parallel-threshold``
-item to the minimal amount of user contexts needed to start the
-parallel execution. In any given simulation round, if that amount is
-not reached, the contexts will be run sequentially directly by the
-main thread (thus saving the synchronization costs). Note that this
-option is mainly useful when the grain of the user code is very fine,
-because our synchronization is now very efficient.
-
When parallel execution is activated, you can choose the
synchronization schema used with the ``contexts/synchro`` item,
which value is either:
.. code-block:: shell
- --cfg=tracing:yes --cfg=tracing/uncategorized:yes --cfg=triva/uncategorized:uncat.plist
+ --cfg=tracing:yes --cfg=tracing/uncategorized:yes
- The first parameter activates the tracing subsystem, the second
+ The first parameter activates the tracing subsystem, and the second
tells it to trace host and link utilization (without any
- categorization) and the third creates a graph configuration file to
- configure Triva when analysing the resulting trace file.
+ categorization).
- MSG or SimDag-based simulator and categorized traces (you need to
declare categories and classify your tasks according to them)
.. code-block:: shell
- --cfg=tracing:yes --cfg=tracing/categorized:yes --cfg=triva/categorized:cat.plist
+ --cfg=tracing:yes --cfg=tracing/categorized:yes
- The first parameter activates the tracing subsystem, the second
- tells it to trace host and link categorized utilization and the
- third creates a graph configuration file to configure Triva when
- analysing the resulting trace file.
+ The first parameter activates the tracing subsystem, and the second
+ tells it to trace host and link categorized utilization.
- SMPI simulator and traces for a space/time view:
message sizes, as protocols may adapt to different message sizes. With
this option, a series of message sizes and factors are given, helping
the simulation to be more realistic. For instance, the current default
-value means that messages with size 65472 and more will get a total of
+value means that messages with size 65472 bytes and more will get a total of
MAX_BANDWIDTH*0.940694, messages of size 15424 to 65471 will get
MAX_BANDWIDTH*0.697866, and so on (where MAX_BANDWIDTH denotes the
bandwidth of the link).
so this example contains two sections. Furthermore, each section
consists of three values.
-1. The first value denotes the minimum size for this section to take effect;
+1. The first value denotes the minimum size in bytes for this section to take effect;
read it as "if message size is greater than this value (and other section has a larger
first value that is also smaller than the message size), use this".
In the first section above, this value is "1".
