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sst_frequently_asked_questions.html
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<HTML>
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<HEAD>
<title>Questions</title>
<style>
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</HEAD>
<BODY>
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<BR>
<fieldset>
<legend>
<I>Question</I>:
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question text?</a>
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<td bgcolor="lightgreen">
<center>RANK</center>
</TD>
</TR>
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<P>
<I>Response</I>: <BR>
<I>Definition</I>: <a name="keyword">keyword</a> = <BR>
<I>Abbreviation</I>: <a name="ASDF">ASDF</a><BR>
</P>
<P>
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<I>References</I>:
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<LI><a href=""></a></LI>
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<I>Related questions</I>:
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<LI><a href="#"></a></LI>
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This single HTML file is intended to be self contained but has links to external resources.
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This file is not intended to be read linearly. Follow the links from a given question to other related questions.
</P>
<P> </P>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="What makes SST distinct from other DES options?">
What makes SST distinct from other DES options?</a>
</legend>
<P><I>Response</I>: <BR>
SST as a framework for DES is not focused on a specific problem or domain.
<P>SST supports distributed computation using MPI.</P>
<P>
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<P>
<I>Related questions</I>:
<UL>
<LI><a href="#"></a></LI>
</UL>
</P>
-->
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="what are the major concepts in SST?">
what are the major concepts in SST?</a>
</legend>
<P>
<I>Response</I>:
<UL>
<LI><a href="#what is an SST element?">elements</a> are a collection of componenets</LI>
<LI><a href="#what is an SST component?">components</a> are connected to links via ports</LI>
<LI>composition (implemented as <a href="#what is a project driver file?">"project driver file"</a>)
which specifies <a href="#what is an SST link?">links</a> between components.</LI>
<LI>events, which are transmitted via links between components</LI>
<LI><a href="#what is an SST subComponent?">subcomponents</a> - shares common base class with Component.
Do not need to communicate with component via links. Cannot exist by themselves
<LI><a href="#what is an SST Module?">modules</a> - self-contained functionality (no access to Component class functionality.
Do not need to communicate with component via links. Cannot exist by themselves. [citation: <a href="https://github.com/sstsimulator/sst-tutorials/blob/master/P38_Nov2020/01_Overview_Using.pptx">slide 50</a>]
<LI>clock, to progress ticks
</UL>
</P>
<img src="pictures/components_and_link.png">
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="what is a project driver file?">
what is a project driver file?</a>
</legend>
<P>
<I>Response</I>: A Python script that specifies <a href="#what is an SST component?">components</a>,
<a href="#what is an SST subComponent?">subComponents</a>, and <a href="#what is an SST link?">links</a>.<BR>
Also can specify parameters per component and subComponent.
</P>
<P>
<I>Reference</I>: <a href="https://sst-simulator.org/SSTPages/SSTUserPythonFileFormat/">https://sst-simulator.org/SSTPages/SSTUserPythonFileFormat/</a>
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="what is an SST element?">
what is an SST element?</a>
</legend>
<P>
<I>Response</I>: a collection of components in a single .so file. Example from <code>sst-info</code>:
<pre>
ELEMENT 1 = switch ()
Num Components = 1
Component 0: SwitchComponent
CATEGORY: UNCATEGORIZED COMPONENT
</pre>
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="what is an SST link?">
what is an SST link?</a>
</legend>
<P>
<I>Response</I>: A Python class that connects two SST components.<BR>
Each component has a port.
</P>
<P>
<pre>
#!/usr/bin/env python3
import sst
compA = sst.Component("Comp A", "dummy.Component")
compB = sst.Component("Comp B", "dummy.Component")
link = sst.Link("mylink")
link.connect((compA, "myPort", "10ns"), (compB, "myPort", "10ns"))
</pre>
</p>
<P>
In a C++ component, poll or interrupt with EventHandler
</p>
<P>
<I>Reference</I>: <a href="https://sst-simulator.org/SSTPages/SSTUserPythonFileFormat/#links">https://sst-simulator.org/SSTPages/SSTUserPythonFileFormat/#links</a>
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="what is an SST component?">
what is an SST component?</a>
</legend>
<P>
<I>Response</I>: A C++ file and .h header that performs the simulation.<BR>
SST Components have ports and send events over links to communicate with other components.<BR>
SST Components can load <a href="#what is an SST subComponent?">SubComponents</a> and Modules for additional functionality.
</P>
<P>
<I>Related questions</I>
<UL>
<LI><a href="#what is an SST subComponent?">what is an SST subComponent?</a></LI>
<LI><a href="#what is an SST link?">what is an SST link?</a></LI>
</UL>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="what is an SST subComponent?">
what is an SST subComponent?</a>
</legend>
<P>
<I>Response</I>: A C++ file and .h header that can be used for supplemental functionality. <BR>
</P>
<P>
<I>Why use a subComponent?</I>:
<UL>
<LI>modularity of functionality between components
<LI>enables common interfaces to other components
</UL>
</P>
<P>Example:
<pre>
#!/usr/bin/env python3
import sst
core = sst.Component(“core”, “miranda.BaseCPU”)
core.addParams({ “clock” : “2.4GHz” })
gen = core.setSubComponent(“generator”, “miranda.STREAMBenchGenerator”)
cache = sst.Component(“L1”, “memHierarchy.Cache”)
mctrl = sst.Component(“memctrl”, “memHierarchy.MemController”)
memory = mctrl.setSubComponent(“backend”, “memHierarchy.simpleMem”)
</pre>
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="what is an SST Module?">
what is an SST Module?</a>
</legend>
<P>
<I>Response</I>: A C++ file and .h header that can be used for supplemental functionality. <BR>
Modules don't access base class API.
Statistics are not available. Ports are not available.
Modules are considered user facing. Can be specified in Python as a parameter.
</P>
<P>
<I>Why use a Module</I>:
<UL>
<LI>modularity of functionality between components
<LI>enables common interfaces to other components
</UL>
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="What are SST extensions?">
What are SST extensions?</a>
</legend>
<P>
<I>Response</I>:
Purpose is to enable decomposition of complicated components. Component extensions cannot be run independently. Status: stable but not official; may have bugs.
Component extensions are in Beta and will eventually be made official; intent is for long-term support.
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="what is an SST Event?">
what is an SST Event?</a>
</legend>
<P>
<I>Response</I>: A unit of communication sent between two SST components over a link.<BR>
</P>
<P>
Examples of standardized interfaces: <BR>
<a href="https://github.com/sstsimulator/sst-core/tree/master/src/sst/core/interfaces">https://github.com/sstsimulator/sst-core/tree/master/src/sst/core/interfaces</a>
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="what files are required for a simulation?">
what files are required for a simulation?</a>
</legend>
<P>
<I>Response</I>:
<UL>
<LI>a "project driver file" as a Python script (.py)
<LI>at least one Component written as C++ source code
<LI>a .h header for the component.
</UL>
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="what elements are registered in SST?">
what elements are registered in SST?</a>
</legend>
<P>
<I>Response</I>: SST Core maintains a database of registered libraries. <BR>The list of registered elements can be queried using <BR><code>sst-info</code>
</P>
<P>
</p>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="how do events appear in a component?">
how do events appear in a component?</a>
</legend>
<P>
<I>Response</I>:
<UL>
<LI>Polled: Register a clock handler to poll the link
<LI>Interrupt: Register an event handler to be called when an event arrives
<LI>Both: Receive events on interrupt, send events on clock
</UL>
source: <a href="https://www.osti.gov/servlets/purl/1506211">slide 15</a>
</P>
<P>
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<I>References</I>:
<UL>
<LI><a href=""></a></LI>
</UL>
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<P>
<I>Related questions</I>:
<UL>
<LI><a href="#"></a></LI>
</UL>
</P>
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</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="What does ELI stand for?">
What does ELI stand for?</a>
</legend>
<P>
<I>Abbreviation</I>: <a name="ELI">ELI</a> = Element Library Information<BR>
</P>
<P>
<!--
<I>References</I>:
<UL>
<LI><a href=""></a></LI>
</UL>
</P>
<P>
<I>Related questions</I>:
<UL>
<LI><a href="#"></a></LI>
</UL>
</P>
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</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="how to register a component in SST?">
how to register a component in SST?</a>
</legend>
<P>
<I>Response</I>: sst-register
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="what is the simulation lifecycle in SST?">
what is the simulation lifecycle in SST?</a>
</legend>
<P>
Description from <a href="https://www.osti.gov/servlets/purl/1506211">slide 19</a>; see also <a href="https://github.com/sstsimulator/sst-tutorials/blob/master/P38_Nov2020/01_Overview_Using.pptx">slide 20</a>
<OL>
<LI>Birth</LI>
<UL>
<LI>Create graph of components using Python configuration file
<LI>Partition graph and assign components to MPI ranks
<LI>Instantiate components
<LI>Connect components via links
<LI>Initialize components using their init() functions
<LI>Setup components using their setup() functions
</UL>
<LI>Life</LI>
<UL>
<LI>Send events
<LI>Manage clock and event handlers
</UL>
<LI>Death</LI>
<UL>
<LI>Finalize components using their finish() functions
<LI>Output statistics
<LI>Cleanup simulation, delete components
</UL>
</OL>
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="what is the component lifecycle in SST?">
what is the component lifecycle in SST?</a>
</legend>
<P>
<I>Response</I>: (from <a href="https://www.osti.gov/servlets/purl/1506211">slide 20</a>, also <a href="https://github.com/sstsimulator/sst-tutorials/blob/master/P38_Nov2020/03_developing-2020-11-05-final.pptx">slide 13</a>)
<OL>
<LI>Graph construction:
<UL>
<LI>define components and links
<LI>partition components to MPI ranks
</UL>
<LI>Construction: call component constructors and parse parameters. See <a href="https://github.com/sstsimulator/sst-tutorials/blob/master/P38_Nov2020/03_developing-2020-11-05-final.pptx">slide 14</a>
<LI>initialize. See <a href="https://github.com/sstsimulator/sst-tutorials/blob/master/P38_Nov2020/03_developing-2020-11-05-final.pptx">slide 15</a>
<UL>
<LI>Components send “init” events to each other over links. Discover neighbors, negotiate parameters, initialize data structures, etc.
<LI>Multiple rounds of communication until no more “init” events are sent
</UL>
<LI>setup ("pre-time")
<UL>
<LI>Each component does its final setup and schedules initial events
</UL>
<LI>run
<UL>
<LI>Actual simulation (time begins)
<LI>Continues until a set time, or all components agree to finish
</UL>
<LI>Complete</LI>
<UL>
<LI>“Post-time” phase analogous to initialization phase
<LI>Components can send “init” events to each other over links
<LI>Multiple rounds, until no more “init” events are sent
</UL>
<LI>finalize</LI>
<UL>
<LI>Simulation complete</LI>
<LI>Write statistics, free memory</LI>
</UL>
</OL>
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="how does SST parallelize simulations?">
how does SST parallelize simulations?</a>
</legend>
<P>
<I>Response</I>: the component-link graph from the <a href="#what is a project driver file?">Python driver file</a> is
<a href="#how does SST partition a simulation?">partitioned</a> and sent to MPI nodes
</P>
<P>
See <a href="https://github.com/sstsimulator/sst-tutorials/blob/master/P38_Nov2020/03_developing-2020-11-05-final.pptx">slides 21-23</a>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="how does SST partition a simulation?">
how does SST partition a simulation?</a>
</legend>
<P>
<I>Response</I>: By default SST tries to partition to load balance and cut long-latency links<BR>
</P>
<P> General Partitioners
<UL>
<LI>linear: Partitions components by dividing Component ID space into roughly equal portions. Components with sequential IDs will be placed close together.
<LI>roundrobin: Partitions components using a simple round robin scheme based on ComponentID. Sequential IDs will be placed on different ranks.
<LI>simple: Simple partitioning scheme which attempts to partition on high latency links while balancing number of components per rank.
<LI>zoltan: zoltan parallel partitioner.
</UL>
</P>
<P>Special Partitioners
<UL>
<LI>single: Allocates all components to rank 0. Automatically selected for serial jobs.
<LI>self: Used when partitioning is already specified in the configuration file.
</uL>
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="what is self partitioning?">
what is self partitioning?</a>
</legend>
<P>
<I>Response</I>: Partitioning can be specified in the python input file<BR>
Use <code>setRank(mpi_rank, thread)</code> on a component.<BR>
User must set rank/thread pairs for all components in system, partial partitions not supported
</P>
<P>
Must set the partitioner to be ”self”. Can be done on command-line: <code>--partitioner=self</code> or
can be done in python file: <code>sst.setProgramOption(”partitioner", ”self")</code>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="how to launch an SST simulation?">
how to launch an SST simulation?</a>
</legend>
<P>
<I>Response</I>:
<OL>
<LI>install SST Core
<LI>register one or more components
<LI><code>sst driver_config.py</code>
</OL>
</P>
<P>
<I>Related questions</I>:
<UL>
<LI><a href="#how to launch a parallel SST simulation?">how to launch a parallel SST simulation?</a></LI>
</UL>
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="how to launch a parallel SST simulation?">
how to launch a parallel SST simulation?</a>
</legend>
<P>
<I>Response</I>: Components distributed among MPI ranks/threads.<BR>
Link latency controls synchronization rate
Two ranks:
<Pre>
mpirun –np 2 sst demo1.py
</pre>
Two threads:
<pre>
sst –n 2 demo1.py
</pre>
Two ranks with two threads each. This will give a warning since we only
have 3 components across 4 ranks/threads
<pre>
mpirun –np 2 sst –n 2 demo1.py
</Pre>
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="how to configure statistics for SST simulation?">
how to configure statistics for SST simulation?</a>
</legend>
<P>
<I>Response</I>:
Components and SubComponents define statistics
<pre>
sst.setStatisticOutput(“sst.statoutputcsv”)
sst.setStatisticOutputOptions({ “filepath” : “stats.csv” })
sst.setStatisticLoadLevel(5)
sst.enableAllStatisticsForAllComponents()
</pre>
source: <a href="https://github.com/sstsimulator/sst-tutorials/blob/master/P38_Nov2020/01_Overview_Using.pptx">slide 55</a>
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="what are all the SST macros?">
what are all the SST macros?</a>
</legend>
<P>
<I>Response</I>: according to <a href="https://sst-simulator.org/SSTPages/SSTDeveloperNewELIMigrationGuide/">ELI guide</a>
the <a href="https://github.com/sstsimulator/sst-core/blob/master/src/sst/core/eli/elementinfo.h#L298">elementinfo.h</a> lists the macros.
However, there are many more.
<P>The full list can be grep'd in the sst-core directory using
<pre>
grep -R "#define SST_ELI" * | cut -d" " -f2 | sed 's/(.*//'g | sort | uniq
</pre>
</P>
A partial list is
<P>
<UL>
<LI>SST_ELI_DOCUMENT_PARAMS
<LI>SST_ELI_DOCUMENT_PORTS - Used by: Components, SubComponents. Macro takes a list of ports available on the element.<BR>
Each port is defined as <code>{ “name”, “description”, vector of supported events }</code><BR>
name and description are string literals
<LI>SST_ELI_DOCUMENT_STATISTICS - Used by: Components, SubComponents. Macro takes a list of statistics that the element can produce; for example<BR>
<code>{ “name”, “description”, “units”, enable level }</code>. <BR>
name, description, and units are string literals.<BR>
enable level is an integer between 1 and 7
<LI>SST_ELI_DOCUMENT_SUBCOMPONENT_SLOTS - sst-core/src/sst/core/eli/subcompSlotInfo.h<BR>
Used by: Components, SubComponent. Macro takes a list of available SubComponentSlots. <BR>
Each slot is defined as <code>{ “slotname”, “description”, “name of superclass” }</code>
name of superclass should be the fully qualified name of the class that defines the slot’s API. <BR>
The superclass inherits from SubComponent, and any subcomponent attached to this slot must inherit from the specified superclass.<BR>
Example: <code>SST::ElementLibrary::SubComponentClass</code>
<LI>SST_ELI_DOCUMENT_PARAMS - Used by: Components, SubComponents, Modules. Each parameter is defined as <code>{ “name”, “description”, “default value” }</code><BR>
If default value is entered as NULL, then there is no default and the parameter is required.<BR>
If default value is an empty string, then it is optional, with no default
<LI>SST_ELI_ELEMENT_VERSION(major, minor, tertiary) - Required for all element types. major, minor and tertiary are integers
<LI>SST_ELI_REGISTER_COMPONENT(class, “library”, “name”, version, “description”, category)
<LI>SST_ELI_REGISTER_CUSTOM_STATISTIC
<LI>SST_ELI_REGISTER_DERIVED
<LI>SST_ELI_REGISTER_EXTERN
<LI>SST_ELI_REGISTER_MODULE(class, “library”, “name”, version, “description”, interface)
<LI>SST_ELI_REGISTER_MODULE_API(class, constructor_args)
<LI>SST_ELI_REGISTER_MODULE_DERIVED
<LI>SST_ELI_REGISTER_MODULE_DERIVED_API(class, base,constructor_args)
<LI>SST_ELI_REGISTER_PARTITIONER(class, “library”, “name” , version, “description”)
<LI>SST_ELI_REGISTER_PYTHON_MODULE(class, “library”, version)
<LI>SST_ELI_REGISTER_SUBCOMPONENT_API(class, constructor_args) - sst-core/src/sst/core/subcomponent.h
<LI>SST_ELI_REGISTER_SUBCOMPONENT_DERIVED(class, “library”, “name”, version, “description”, interface) - sst-core/src/sst/core/subcomponent.h
<LI>SST_ELI_REGISTER_SUBCOMPONENT_DERIVED_API(class, base,constructor_args) - sst-core/src/sst/core/subcomponent.h
</UL>
source: <a href="https://github.com/sstsimulator/sst-tutorials/blob/master/P38_Nov2020/03_developing-2020-11-05-final.pptx">slides 4-11</a>
</P>
<P>
Definitions of arguments:
<UL>
<LI>class: Name of class to register. Must not be quoted, as template expansion uses it.
<LI>base: Name of base class API is derived from. Must not be quoted, as template expansion uses it.
<LI>library: Library name. String literal.
<LI>name: Name used to reference the component, full name is library.name. String literal.
<LI>Example: if library = “merlin” and name = ”hr_router”, then full name is “merlin.hr_router”
<LI>version: Version number of component defined using SST_ELI_ELEMENT_VERSION macro
<LI>description: Brief description of the component. String literal.
<LI>category (Components only): Component category as defined in elibase.h.
<LI>interface (SubComponents and Modules only): Fully qualified class name of the SubComponent/Module that this class inherits from. Must not be qutoted. The interface must be registered as an API using one of the registration commands listed above.
<LI>constructor_args (SubComponent and Module APIs only): types of parameters to be passed to constructor of elements derived from these APIs
</UL>
source: <a href="https://github.com/sstsimulator/sst-tutorials/blob/master/P38_Nov2020/03_developing-2020-11-05-final.pptx">slide 4</a>
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="what are the core APIs in SST?">
what are the core APIs in SST?</a>
</legend>
<P>
<I>Response</I>: <BR>
<UL>
<LI>SST::Simulation - sst/core/simulation.h; Base of the simulation
<LI>SST::Event - sst/core/event.h; Base class for data to send over a SST::Link<BR>
Inherit from this to create your own Event<BR>
Provides base class for <code>Event::Handler<code>
<LI>SST::Component
<LI>SST::Link - sst/core/link.h; Standard mechanism to send/receive data from another component.<BR>
Created via <code>SST::Component::configureLink()<code>
<LI>SST::Param - sst/core/param.h; Holds parameters from ConfigGraph. Handed to Component in constructor
<LI>SST::Output - sst/core/output.h; Utility class to bundle output from SST
<LI>SST::UnitAlgebra
<LI>SST::RNG::SSTRandom
</UL>
source: <a href="https://github.com/sstsimulator/sst-tutorials/blob/master/P38_Nov2020/03_developing-2020-11-05-final.pptx">slide 25</a>
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="what is the default time increment in SST?">
what is the default time increment in SST?</a>
</legend>
<P>
<I>Response</I>: Time in the core is represented by a uint64_t, which counts the number of atomic ticks since simulation start.<BR>
Tick unit can be specified, default is 1 picosecond, which allows nearly 2/3 year of simulated time<BR>
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="Can SST SubComponents be run independently?">
Can SST SubComponents be run independently?</a>
</legend>
<P>
<I>Response</I>: SubComponents have to be coupled to a component.
They aren’t able to run independently since they interact with a Component via an API rather than the Link interface.
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="Does SST coalesce MPI messages between components?">
Does SST coalesce MPI messages between components?</a>
</legend>
<P>
<I>Context</I>: The events being serialized between components are small.
</P>
<P>
<I>Response</I>: yes, but this is not documented because it's not exposed to users or developers. <BR>
Specifically, every MPI rank has a queue per remote thread. Then each queue is serialized at clock sync.
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="Can SST be run without being clocked?">
Can SST be run without being clocked?</a>;
<a name="Can SST be run as a functional simulation?">
Can SST be run as a functional simulation?</a>
</legend>
<P>
<I>Response</I>: "time core" is needed for causality, so probably can't revert to functional simulation.
Could send messages without sync, but that would violate causality and is not supported.
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="If SST were event-driven rather than clocked, would that be faster to execute?">
If SST were event-driven rather than clocked, would that be faster to execute?</a>
</legend>
<P>
<I>Response</I>: Arbitration is clocked. When clocks return nothing, then switching to event-based would be faster.
If there are many elements or lots of activity, then unclocked would be slower.
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="Is there any limit to the nesting of subcomponents??">
Is there any limit to the nesting of subcomponents??</a>
</legend>
<P>
<I>Response</I>: There's no limit imposed by SST.
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="What is the advantage of Subcomponents over libraries?">
What is the advantage of Subcomponents over libraries?</a>
</legend>
<P>
<I>Response</I>: The value of SST Subcomponents is dynamic loading at runtime.
Subcomponents have unique ports and unique statistics.
Parent component does not need to be aware of subcomponent's ports.
Subcomponents can be specified directly in Python or as parameters. <BR>
Statically-linked C++ libraries are viable alternative to subcomponents.
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="where does SST graph construction take place in an MPI simulation?">
where does SST graph construction take place in an MPI simulation?</a>
</legend>
<P>
<I>Response</I>: Graph construction takes place in Python and is serial on rank=0.
Partitioner can be parallelized using Zoltan.
</P>
</fieldset>
<BR>
<fieldset>
<legend>
<I>Question</I>:
<a name="how does SST generate graphviz plots?">
how does SST generate graphviz plots?</a>
</legend>
<P>
<I>Response</I>:
<code>sst --output-dot=pic.gv --run-mode=init config.py</code>
</P>
<p>
There are two graphs generated, "connections" and "sst_simulation". The "connections" graph is the pre-partitioned graph,
the "sst_simulation" graph shows which MPI rank and which thread hosts each node in the graph.
See <a href="https://github.com/sstsimulator/sst-core/blob/master/src/sst/core/cfgoutput/dotConfigOutput.cc">
https://github.com/sstsimulator/sst-core/blob/master/src/sst/core/cfgoutput/dotConfigOutput.cc</a>
</P>
</fieldset>
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