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-\documentclass[11pt]{article}

-\usepackage{fancyhdr}

-\usepackage[dvips]{graphicx} 

-\usepackage{amsmath,amssymb} 

-\usepackage{epsfig}

-\usepackage{calc}

-

-\newcommand{\simname}{BookSim~}

-

-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

-

-% Setup the margin sizes.

-

-\evensidemargin = 0in

-\oddsidemargin = 0in

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-

-\topmargin = -0.5in

-\textheight = 9in

-

-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

-

-\author{Brian Towles and William J. Dally}

-\title{\simname 1.0 User's Guide}

-

-\begin{document}

-

-\maketitle

-\tableofcontents

-

-\pagestyle{fancy}

-%\renewcommand{\chaptermark}[1]{\markboth{#1}{}}

-\renewcommand{\sectionmark}[1]{\markright{\thesection\ #1}}

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-    \renewcommand{\headrulewidth}{0pt} % and the line

-    \renewcommand{\footrulewidth}{0pt} % and the line

-} 

-

-

-%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

-

-\newenvironment{opt_list}[1]{\begin{list}{}{\renewcommand{\makelabel}[1]%

-{\texttt{##1}\hfil}\settowidth{\labelwidth}{\texttt{#1}}\setlength{\leftmargin}%

-{\labelwidth+\labelsep}}}{\end{list}}

-

-\section{Introduction}

-

-This document describes the use of the \simname interconnection

-network simulator.  The simulator is designed as a companion to the

-textbook ``Principles and Practices of Interconnection Networks''

-(PPIN) published by Morgan Kaufmann (ISBN: 0122007514) and it is

-assumed that is reader is familiar with the material covered in that

-text.

-

-This user guide is fairly brief as, with most simulators, the best way

-to learn and {\it understand} the simulator is to study the code.

-Most of the simulator's components are designed to be modular so tasks

-such as adding a new routing algorithm, topology, or router

-microarchitecture should not require a complete redesign of the code.

-Once you have downloaded the code, compiled it, and run a simple

-example (Section~\ref{sec:get_started}), the more detailed examples of

-Section~\ref{sec:examples} give a good overview of the capabilities of

-the simulator.  A list of configuration options is provided in

-Section~\ref{sec:config_params} for reference.

-

-\section{Getting started}

-\label{sec:get_started}

-

-\subsection{Downloading and building the simulator}

-\label{sec:download}

-

-The latest version of the simulator is available from

-\texttt{http://cva.stanford.edu} as a compressed tar archive.  UNIX/Linux

-users can extract this archive using the tar utility

-\begin{verbatim}

-  tar xvfz booksim-1.0.tar.gz  

-\end{verbatim}

-Windows users can use a compression program such as WinZip to extract

-the archive.

-

-The simulator itself is written in C++ and has been specifically

-tested with GNU's G++ compiler (version $\ge3$).  In addition, both a

-LEX and YACC tool (also known as FLEX and BISON) are needed to create

-the configuration parser.  These are standard tools in any UNIX/Linux

-development environment.  It is suggested that Windows users download

-the CYGWIN versions (\texttt{http://www.cygwin.com}) of these UNIX

-development tools to simplify their compilation process.  The

-\texttt{Makefile} should be edited so that the first lines give the

-paths to the tools.  At Stanford, for example, the compiler, YACC, and

-LEX are stored in the \texttt{/usr/pubsw/bin} directory.  The

-\texttt{Makefile} reflects this:

-\begin{verbatim}

-CPP    = /usr/pubsw/bin/g++

-YACC   = /usr/pubsw/bin/byacc -d

-LEX    = /usr/pubsw/bin/flex

-\end{verbatim}

-Then, the simulator can be compiled by running \texttt{make} in the

-directory that contains the \texttt{Makefile}.

-

-\subsection{Running a simulation}

-\label{sec:run_example}

-

-The syntax of the simulator is simply

-\begin{verbatim}

-  booksim [configfile]

-\end{verbatim}

-The optional parameter \texttt{configfile} is a file that contains

-configuration information for the simulator.  So, for example, to

-simulate the performance of a simple $8 \times 8$ torus (8-ary 2-cube)

-network on uniform traffic, a configuration such as the one shown in

-Figure~\ref{fig:config_example} could be used.  This particular

-configuration is stored in \texttt{examples/torus88}.

-

-\begin{figure}

-\begin{verbatim}

-  // Topology

-  topology = torus;

-  k        = 8;

-  n        = 2;

-

-  // Routing

-  routing_function = dim_order;

-

-  // Flow control

-  num_vcs = 2;

-

-  // Traffic

-  traffic        = uniform;

-  injection_rate = 0.15;

-\end{verbatim}

-\caption{Example configuration file for simulating a 8-ary 2-cube

-network.}

-\label{fig:config_example}

-\end{figure}

-

-In addition to specifying the topology, the configuration file also

-contains basic information about the routing algorithm, flow control,

-and traffic.  This simple example uses dimension-order routing and, to

-ensure deadlock-freedom of this routing function in the torus, two

-virtual channels are required.  The \texttt{injection\_rate} parameter

-is added to tell the simulator to inject 0.15 flits per simulation

-cycle per node.  Because the simulator operates at the flit level,

-most parameters are specified in units of flits as is the case with

-the \texttt{injection\_rate}.  Also, any line of the configuration

-that begins with \texttt{//} is treated as a comment and ignored by

-the simulator.  A detailed list of configuration parameters is given in

-Section~\ref{sec:config_params}.

-

-\subsection{Simulation output}

-

-Continuing our example, running the torus simulation produces the

-output shown in Figure~\ref{fig:sim_output}.  Each simulation has

-three basic phases: warm up, measurement, and drain.  The length of

-the warm up and measurement phases is a multiple of a basic sample

-period (defined by \texttt{sample\_period} in the configuration).  As

-shown in the figure, the current latency and throughput (rate of

-accepted packets) for the simulation is printed after each sample

-period.  The overall throughput is determined by the lowest throughput

-of all the destination in the network, but the average throughput is

-also displayed.

-

-\begin{figure}

-\begin{verbatim}

-%=================================

-% Average latency = 6.02008

-% Accepted packets = 0.11 at node 52 (avg = 0.147094)

-% latency change    = 1

-% throughput change = 1

-

-...

-

-% Warmed up ...

-%=================================

-% Average latency = 6.0796

-% Accepted packets = 0.119 at node 5 (avg = 0.148266)

-% latency change    = 0.00562457

-% throughput change = 0.00379387

-

-...

-

-% Draining all recorded packets ...

-% Draining remaining packets ...

-====== Traffic class 0 ======

-Overall average latency = 6.09083 (1 samples)

-Overall average accepted rate = 0.149475 (1 samples)

-Overall min accepted rate = 0.138551 (1 samples)

-\end{verbatim}

-\caption{Simulator output from running the \texttt{examples/torus88}

-configuration file.}

-\label{fig:sim_output}

-\end{figure}

-

-After the warm up periods have passed, the simulator prints the

-``\texttt{Warmed up}'' message and resets all the simulation statistics.

-Then, the measurement phase begins and statistics continue to be

-reported after each sample period.  Once the measurement periods have

-passed, all the measurement packets are drained from the network

-before final latency and throughput numbers are reported.  Details of

-the configuration parameters used to control the length of the

-simulation phases are covered in Section~\ref{sec:sim_params}.

-

-\section{Examples}

-\label{sec:examples}

-

-One of the most basic performance measures of any interconnection

-network is its latency versus offered load.

-Figure~\ref{fig:lat_vs_load} shows a simple configuration file for

-making this measurement in a 8-ary 2-mesh network under the transpose

-traffic pattern.  This configuration was used to generate Figure 25.2

-in PPIN.  The particular configuration accounts for some small delays

-and pipelining of the input-queued router and also introduces a small

-input speedup to account for any inefficiencies in allocation.  By

-running simulations for many increments of \texttt{injection\_rate},

-the average latency curve can be found.  Then, to compare the

-performance of dimension-order routing against several other routing

-algorithms, for example, the \texttt{routing\_function} option can be

-changed.

-

-\begin{figure}

-\begin{verbatim}

-// Topology

-

-topology = mesh;

-k = 8;

-n = 2;

-

-// Routing

-

-routing_function = dim_order;

-

-// Flow control

-

-num_vcs     = 8;

-vc_buf_size = 8;

-

-wait_for_tail_credit = 1;

-

-// Router architecture

-

-vc_allocator = islip;

-sw_allocator = islip;

-alloc_iters  = 1;

-

-credit_delay   = 2;

-routing_delay  = 1;

-vc_alloc_delay = 1;

-

-input_speedup     = 2;

-output_speedup    = 1;

-internal_speedup  = 1.0;

-

-// Traffic

-

-traffic                = transpose;

-const_flits_per_packet = 20;

-

-// Simulation

-

-sim_type       = latency;

-injection_rate = 0.1;

-\end{verbatim}

-\caption{A typical configuration file (\texttt{examples/mesh88\_lat})

-for creating a latency versus offered load curve for a 8-ary 2-mesh

-network.}

-\label{fig:lat_vs_load}

-\end{figure}

-

-Figure~\ref{fig:fly_dist} shows a configuration file that can be used

-to determine the distribution of packet latencies in a 2-ary 6-fly

-network that uses age-based arbitration.  Note the use of the

-\texttt{priority} configuration parameter along with the

-\texttt{select} allocators that account for packet priorities.  The

-simulator does not output latency distributions by default, but by

-editing \texttt{trafficmanager.cpp}, setting the configuration

-variable \texttt{DISPLAY\_LAT\_DIST} to true, and recompiling, the

-distribution will be displayed at the end of the simulation.  This

-technique was used to produced the distribution shown in Figure 25.12

-of PPIN.

-

-\begin{figure}

-\begin{verbatim}

-// Topology

-

-topology = fly;

-k = 2;

-n = 6;

-

-// Routing

-

-routing_function = dest_tag;

-

-// Flow control

-

-num_vcs     = 8;

-vc_buf_size = 8;

-

-wait_for_tail_credit = 1;

-

-// Router architecture

-

-vc_allocator = select;

-sw_allocator = select;

-alloc_iters  = 1;

-

-credit_delay   = 2;

-routing_delay  = 1;

-vc_alloc_delay = 1;

-

-input_speedup     = 2;

-output_speedup    = 1;

-internal_speedup  = 1.0;

-

-// Traffic

-

-traffic                = uniform;

-const_flits_per_packet = 20;

-priority               = age;

-

-// Simulation

-

-sim_type       = latency;

-injection_rate = 0.1;

-\end{verbatim}

-\caption{A configuration file (\texttt{examples/fly26\_age}) for

-finding the distribution of packet latencies using age-based

-arbitration.}

-\label{fig:fly_dist}

-\end{figure}

-

-As a final example, Figure~\ref{fig:single} shows the use of the

-special single-node topology to test the performance of a switch

-allocator --- in this case, the iSLIP allocator.  The

-\texttt{in\_ports} and \texttt{out\_ports} options set up a simulation

-of an $8\times 8$ crossbar.

-

-\begin{figure}

-\begin{verbatim}

-// Topology

-

-topology  = single;

-in_ports  = 8;

-out_ports = 8;

-

-// Routing

-

-routing_function = single;

-

-// Flow control

-

-vc_allocator = islip;

-sw_allocator = islip;

-alloc_iters  = 2;

-

-num_vcs     = 8;

-vc_buf_size = 1000;

-

-wait_for_tail_credit = 0;

-

-// Simulation

-

-sim_type       = latency;

-injection_rate = 0.1;

-\end{verbatim}

-\caption{A single-node configuration file (\texttt{examples/single})

-for testing the performance of a switch allocator.}

-\label{fig:single}

-\end{figure}

-

-\section{Configuration parameters}

-\label{sec:config_params}

-

-All information used to configure a simulation is passed through a

-configuration file as illustrated by the example in

-Section~\ref{sec:run_example}.  This section lists the existing

-configuration parameters --- a user can incorporate additional options

-by changing the \texttt{booksim\_config.cpp} file.

-

-\subsection{Topologies}

-\label{sec:topos}

-

-The \texttt{topology} parameter determines the underlying topology of the

-network and the simulator supports four basic topologies:

-\begin{opt_list}{single}

-\item[fly] A $k$-ary $n$-fly (butterfly) topology. The \texttt{k}

-parameter determines the network's radix and the \texttt{n} parameter

-determines the network's dimension.

-

-\item[mesh] A $k$-ary $n$-mesh (mesh) topology. The \texttt{k}

-parameter determines the network's radix and the \texttt{n} parameter determines

-the network's dimension.

-

-\item[single] A network with a single node, used for testing single

-router performance.  The number of input and output ports for the node

-is determined by the \texttt{in\_ports} and \texttt{out\_ports} parameters,

-respectively.

-

-\item[torus] A $k$-ary $n$-cube (torus) topology.  The \texttt{k}

-parameter determines the network's radix and the \texttt{n} parameter determines

-the network's dimension.

-\end{opt_list}

-

-Both the \texttt{mesh} and \texttt{torus} topologies support the

-addition of random link failures with the \texttt{link\_failures}

-parameter.  The value of \texttt{link\_failures} determines the number

-of channels that are randomly removed from the topology and are thus

-no longer available for forwarding packets.  Moreover, the

-randomization for failed channels is controlled by selecting an

-integer value for the \texttt{fail\_seed} parameter --- a fixed seed

-gives a fixed set of failed channels, independent of other

-randomization in the simulation.  Also, note that only certain routing

-functions support this feature (see Section~\ref{sec:routing_algs}).

-

-\subsection{Routing algorithms}

-\label{sec:routing_algs}

-

-The \texttt{routing\_function} parameter selects a routing algorithm

-for the topology.  Many routing algorithms need multiple virtual

-channels for deadlock freedom (VCDF).

-

-\begin{opt_list}{dim\_order\_bal}

-

-\item[dim\_order] Dimension-order routing.  Works for the

-\texttt{mesh} topology (1 VCDF) and for the \texttt{torus} topology (2

-VCDF).

-

-\item[dim\_order\_bal] Dimension-order routing for the

-\texttt{torus} topology with a more balanced use of VCs to

-avoid deadlock (2 VCDF).

-

-\item[dim\_order\_ni] A non-interfering version of

-dimension-order routing.  Works on the \texttt{torus} or \texttt{mesh}

-topology and requires one VC per network terminal.

-

-\item[min\_adapt] A minimal adaptive routing algorithm for

-the \texttt{mesh} topology (2 VCDF) and for the \texttt{torus}

-topology (3 VCDF).

-

-\item[planar\_adapt] Planar-adaptive routing for the

-\texttt{mesh} topology (2 VCDF).  Supports routing around failed channels.

-

-\item[romm] ROMM routing for the \texttt{mesh} (2 VCDF).

-Load is balanced by routing in two phases: one from the source to a

-random intermediate node in the minimal quadrant and a second from the

-intermediate to the destination.

-

-\item[romm\_ni] A non-interfering version of ROMM routing for

-the \texttt{mesh} that requires one VC per network terminal.

-

-\item[single] A dummy routing function used for the

-\texttt{single} topology.

-

-\item[valiant] Valiant's randomized routing algorithm for the

-\texttt{mesh} (2 VCDF) and \texttt{torus} (4 VCDF) topology.

-

-\item[valiant\_ni] A non-interfering version of Valiant's algorithm

-for the \texttt{torus} that requires 4 VCs per network terminal.

-

-\end{opt_list}

-

-Also, the simulator code is structured so that additional routing

-algorithms can be added with minimal changes to the overall simulator

-(see the \texttt{routefunc.cpp} file in the simulator's source code).

-

-\subsection{Flow control}

-

-The simulator supports basic virtual-channel flow control with

-credit-based backpressure.  

-

-\begin{opt_list}{wait\_for\_tail\_credit}

-

-\item[num\_vcs] The number of virtual channels per physical channel.

-

-\item[vc\_buf\_size] The depth of each virtual in flits.

-

-\item[voq] If non-zero, use virtual-output queuing.  With virtual

-output queuing, a separate virtual channel is assigned to each

-destination in the network.  This option is most useful when used with

-a non-interfering routing algorithm (Section~\ref{sec:routing_algs}).

-  

-\item[wait\_for\_tail\_credit] If non-zero, do not reallocate a virtual

-channel until the tail flit has left that virtual channel.  This

-conservative approach prevents a dependency from being formed between

-two packets sharing the same virtual channel in succession.

-\end{opt_list}

-

-\subsection{Router organizations}

-

-The simulator also supports two different router microarchitectures.

-The input-queued router follows the general organization described in

-PPIN while the event-driven router is modeled after the router used in

-the Avici TSR and described in U.S. Patent 6,370,145.  The

-microarchitecture is selected using the \texttt{router} option.  Also,

-both routers share a small set of options.

-

-\begin{opt_list}{internal\_speedup}

-\item[credit\_delay] The processing delay (in cycles) for a credit.

-Does not include the wire delay for transmitting the credit.

-

-\item[internal\_speedup] An arbitrary speedup of the internals of the

-routers over the channel transmission rate.  For example, a speedup

-1.5 means that, on average, 1.5 flits can be forwarded by the router

-in the time required for a single flit to be transmitted across a

-channel.  Also, the configuration parser expects a floating point

-number for this field, so integer speedups should also include a

-decimal point (e.g. ``2.0'').

-

-\item[output\_delay] The processing delay incurred in the output queue

-of a router.

-\end{opt_list}

-

-\subsubsection{The input-queued router}

-\label{sec:iq_router}

-

-The input-queued router (\texttt{router = iq}) follows the pipeline

-described in PPIN of route computation, virtual-channel allocation,

-switch allocation, and switch traversal.  There are several options

-specific to the input-queued router.

-

-\begin{opt_list}{st\_prepare\_delay}

-

-\item[input\_speedup] An integer speedup of the input ports in space.

-A speedup of 2, for example, gives each input two input ports into the

-crossbar.  Access to these ports is statically allocated based on the

-virtual channel number: virtual channel $v$ at input $i$ is connected

-to port $i \cdot s + (v \mod s)$ for an input speedup of $s$.

-

-\item[output\_speedup] An integer speedup of the output ports in

-space.  Similar to \texttt{input\_speedup}

-

-\item[routing\_delay] The delay (in cycles) of route computation.

-

-\item[sw\_allocator] The type of allocator used for switch allocation.

-See Section~\ref{sec:alloc} for a list of the possible allocators.

-

-\item[sw\_alloc\_delay] The delay (in cycles) of switch allocation.

-

-\item[vc\_allocator] The type of allocator used for virtual-channel

-allocation.  See Section~\ref{sec:alloc} for a list of the possible

-allocators.

-

-\item[vc\_alloc\_delay] The delay (in cycles) of virtual-channel

-allocation.

-

-\end{opt_list}

-

-\subsubsection{The event-driven router}

-\label{sec:event_router}

-

-The event-driven router (\texttt{router = event}) is a

-microarchitecture designed specifically to support a large number of

-virtual channels (VCs) efficiently.  Instead of continuously polling

-the state of the virtual channels, as in the input-queued router, only

-changes in VC state are tracked.  The efficiency then comes from the

-fact that the number of state changes per cycle is constant and

-independent of the number of VCs.

-

-\subsection{Allocators}

-\label{sec:alloc}

-

-Many of the allocators used in the simulator are configurable (see

-the input-queued router in Section~\ref{sec:iq_router}) and several

-allocation algorithms are available.

-\begin{opt_list}{wavefront}

-

-\item[max\_size] Maximum-size matching. 

-\item[islip] iSLIP separable allocator.

-\item[pim] Parallel iterative matching separable allocator.

-\item[loa] Lonely output allocator.

-\item[wavefront] Wavefront matching.

-\item[select] Priority-based allocator.  Allocation is performed as in

-iSLIP, but with preference towards higher priority packets (see

-\texttt{priority} option in Section~\ref{sec:traffic}).

-

-\end{opt_list}

-

-Allocation can also be improved by performing multiple iterations of

-the algorithm and the number of iterations is controlled by the

-\texttt{alloc\_iters} parameter.

-

-\subsection{Traffic}

-\label{sec:traffic}

-

-The rate at which flits are injected into the simulator is set using

-the \texttt{injection\_rate} option.  The simulator's cycle time is a

-flit cycle, the time it takes a single flit to be injected at a

-source, and the injection rate is specified in flits per flit cycle.

-For example, setting \texttt{injection\_rate = 0.25} means that each

-source injects a new flit one of every four simulator cycles.  The

-injection process can also be specified as either Bernoulli

-(\texttt{injection\_process = bernoulli}) or an on-off process

-(\texttt{injection\_process = on\_off}).  The burstiness of the latter

-injection process is controlled via the \texttt{burst\_alpha} and

-\texttt{burst\_beta} parameter.  See PPIN Section 24.2.2 for a

-description of the on-off process and its parameters.

-

-The unit of injection is packets, which may be comprised of many

-flits.  The number of flits per packet is set using the

-\texttt{const\_flits\_per\_packet} option.  Each packet may also have an

-associated priority, either age-based (\texttt{age}) or none

-(\texttt{none}), as specified by the \texttt{priority} option.

-

-The simulator also supports several different traffic patterns that

-are specified using the \texttt{traffic} option.  To describe these

-patterns, we use the same notation of PPIN Section 3.2: $s_i$ ($d_i$)

-denotes the $i^\textrm{th}$ bit of the source (destination) address

-whereas $s_x$ ($d_x$) denotes the $x^\textrm{th}$ radix-$k$ digit of

-the source (destination) address.  The bit length of an address is $b

-= \log_2 N$, where $N$ is the number of nodes in the network.

-

-\begin{opt_list}{transpose}

-\item[uniform] Each source sends an equal amount of traffic to each

-destination (\texttt{traffic = uniform}).

-\item[bitcomp] Bit complement. $d_i = \neg s_i$.

-\item[bitrev] Bit reverse. $d_i = s_{b-i-1}$.

-\item[shuffle] $d_i = s_{i-1 \mod b}$.

-\item[transpose] $d_i = s_{i+b/2 \mod b}$.

-\item[tornado] $d_x = s_x + \lceil k/2 \rceil - 1 \mod k$.

-\item[neighbor] $d_x = s_x + 1 \mod k$.

-\item[randperm] Random permutation.  A fixed permutation traffic

-pattern is chosen uniformly at random from the set of all

-permutations.  The seed used to generate this permutation is set by

-the \texttt{perm\_seed} option.  So, randomly selecting values for

-\texttt{perm\_seed} gives a random sampling of permutation while a

-fixed value of \texttt{perm\_seed} allows the same permutation to be

-used for several experiments.

-\end{opt_list}

-

-\subsection{Simulation parameters}

-\label{sec:sim_params}

-

-The duration and other aspects of a simulation are controlled using

-the set of simulation parameters.

-

-\begin{opt_list}{warmup\_periods}

-

-\item[sim\_type] A simulation can either focus on

-\texttt{throughput} or \texttt{latency}.  The key difference between

-these two types is that a \texttt{latency} simulation will wait for

-all measurement packets to drain before ending the simulation to

-ensure an accurate latency measurement.  In \texttt{throughput}

-simulations, this final drain step is eliminated to allow simulation

-of networks operating beyond their saturation point.

-

-\item[sample\_period] The sample period is expressed in simulator

-cycles and is used as a multiplier when specifying the warm-up length

-of a simulation and the maximum number of samples.  Also, intermediate

-statistics are displayed once every \texttt{sample\_period} cycles.

-

-\item[warmup\_periods] The length of the simulator warm up expressed

-as a multiple of the \texttt{sample\_period}.  After warming up, all

-statistics counters are reset.

-

-\item[max\_samples] The total length of simulation expressed as a

-multiple of the \texttt{sample\_period}.

-

-\item[latency\_thres] If the sampled latency of the current simulation

-exceeds \texttt{latency\_thres}, the simulation is immediately ended.

-

-\item[sim\_count] The number of back-to-back simulations to run for the

-given configuration.  Useful for creating ensemble averages of

-particular statistics.

-

-\item[seed] A random seed for the simulation.

-

-\item[reorder] A non-zero value indicates that packet order should be

-maintained and reordering time is accounted for in the overall latency.

-

-\end{opt_list}

-

-\appendix

-

-\section{Random number generation}

-

-The simulator uses Knuth's integer and floating point pseudorandom

-number generators.  These algorithms and their explanations appear in

-``The Art of Computer Programming: Seminumerical Algorithms''.

-

-\end{document}
\ No newline at end of file