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StreamIt 2.1.1 Release
======================

This is for the January 29, 2007 release of the StreamIt compiler and
runtime system, version 2.1.1.
$Id: readme.tex.in,v 1.26 2006/09/11 20:04:10 thies Exp $


1  What is this?
----------------

StreamIt is a programming language designed for efficient implementation
of streaming systems, particularly digital signal processing
applications. This is a public release of the StreamIt compiler. While
the compiler is still under active development, we believe this release
should be useful for developing StreamIt applications. See "caveats",
below, and report bugs and feature requests to [email protected].
This compiler should produce functional code for uniprocessor targets,
multicore architectures, clusters of workstations, and the MIT Raw
processor. There is also a runtime library for testing programs through a
Java compiler.

There are two versions of this release. These are:

streamit-src-2.1.1.tar.gz
      "Source release." This contains the full sources of the StreamIt
      compiler and runtime libraries, but no binaries. Build instructions
      are included in the INSTALL file.

streamit-2.1.1.tar.gz
      "Binary release." This contains no sources, but does contain a Java
      jar file with the full compiler.

The StreamIt compiler is built on top of version 1.5B of the Kopi Java
compiler from DMS Decision Management Systems GmbH. The independent
components of the system, including the scheduler, Java runtime library,
C/C++ libraries, the front end, and the StreamIt .str files, are released
subject to the terms of the MIT license agreement. Other components of
the system are released under the terms of the GNU General Public
License; see the COPYING file for details. The binary release also
include class files from the ANTLR LL(k) parser generator.

Several documents on StreamIt are in the docs directory. You can find
more information on our Web page, at http://cag.csail.mit.edu/streamit/.


2  Dependencies
---------------

The StreamIt makefile infrastructure uses the GNU tools, which are
available from http://www.gnu.org. In particular, GNU Make is required to
build; this is the default <tt>make</tt> on Linux machines, and may be
available as <tt>gmake</tt> on other Unix-like machines. The source
release depends on Sun's Java compiler (javac). Both the source and
binary releases require a Java virtual machine for Java version 1.5 or
later; see http://java.sun.com/ for possibilities.

The front end depends on the ANTLR LL(k) parser generator; see
http://www.antlr.org/. If you are using the source release, the ANTLR
classes must be in your Java CLASSPATH when compiling and running the
StreamIt compiler. If you are using the binary release, the required
ANTLR classes are already included in the StreamIt jar file.

The linear optimizations (not turned on by default) depend on the FFTW
library; see http://www.fftw.org/. The StreamIt runtime system currently
only supports fftw-2.1.x, not the newer fftw-3.0 branch. FFTW should be
installed somewhere in your default compiler search path. You need to
build single-precision versions of the library, such that you have
include files sfftw.h, srfftw.h and library files libsfftw.a and
libsrfftw.a. The linear optimizations are turned on only if configure can
find all four files. If you are building FFTW from source, pass the
following options to configure: --enable-shared --enable-type-prefix
--enable-threads
--enable-float.

While this is not a a dependency, the graphviz package from
http://www.graphviz.org contains a viewer, dotty, that will display the
dot files created by the StreamIt compiler.


3  Caveats
----------

This is a snapshot release of the StreamIt compiler. This is a research
compiler; as such, it has several known shortcomings:

  * The compiler works by converting StreamIt syntax to a Java
    intermediate form, and then using a Java compiler. Of note, compiling
    'foo.str' will clobber a file named 'foo.java' in the same directory.

  * The dimensions of a filter field cannot be declared in terms of
    another filter field. That is, code of the following form will fail:

    float->float filter Foo {
      int N = 10;
      float[N] coeff;
      ...
    }

    In such cases, just declare the array to be float[10].

  * In splitjoins and feedbackloops, splitters and joiners cannot be
    specified from within conditional code. For example, the following
    code causes problems:

    float->float splitjoin Bar {
      if (...) {
        split duplicate;
      } else {
        split roundrobin;
      }
    }

    If you really need such a conditional, then define two separate
    splitjoins (Bar1 and Bar2) and do the test when adding them to a
    parent stream:

    float->float pipeline Parent {
      if (...) {
        add Bar1(); // uses duplicate splitter
      } else {
        add Bar2(); // uses roundrobin splitter
      }
    }  

  * The compiler does not support passing structures or complex numbers
    as stream parameters. This will result in an error such as

    at.dms.util.InconsistencyException: Expected constant arguments to
    init, but found non-constant VarExp:p in parent SIRPipeline
    name=pipe_3

    Structures and complex should work as local variables and as the
    input or output types of filters.

  * Arrays cannot be returned from helper functions.

  * In most back ends, arrays cannot be used as the input or output types
    of streams. This is largely a limitation in the uniprocessor back
    end; you can get equivalent code by using streams of the base type of
    the array, and constructing the array inside the work function if
    necessary.

  * The static blocks are limited (except in the Java library back end)
    in that they act as specified only if every declared variable in the
    static block is assigned to exactly once. Furthermore, there can
    currently be at most one static block in a program.


4  For more info
----------------

The StreamIt home page is at http://cag.csail.mit.edu/streamit/. There
are a number of places you can send electronic mail to:

[email protected]
      General information on StreamIt, to report bugs in the compiler or
      request new language features, or to be added to streamit-users or
      streamit-dev

[email protected]
      Discussion list for application developers and others using the
      StreamIt compiler

[email protected]
      Discussion list for people working on the internals of the StreamIt
      compiler

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  This document was translated from LATEX by HEVEA.