Introduction to spead2

spead2 is an implementation of the SPEAD protocol, with both Python and C++ bindings. The 2 in the name indicates that this is a new implementation of the protocol; the protocol remains essentially the same. Compared to the PySPEAD implementation, spead2:

  • is at least an order of magnitude faster when dealing with large heaps;

  • correctly implements several aspects of the protocol that were implemented incorrectly in PySPEAD (bug-compatibility is also available);

  • correctly implements many corner cases on which PySPEAD would simply fail;

  • cleanly supports several SPEAD flavours (e.g. 64-40 and 64-48) in one module, with the receiver adapting to the flavour used by the sender;

  • supports Python 3;

  • supports asynchronous operation, using asyncio.


There is optional support for ibverbs for higher performance, and pcap for reading from previously captured packet dumps. If the libraries (including development headers) are installed, they will be detected automatically and support for them will be included.

If you are installing spead2 from a git checkout, it is first necessary to run ./ to prepare the configure script and related files. This requires a Python installation with pycparser and jinja2 installed. When building from a packaged download this is not required.

High-performance usage requires larger buffer sizes than Linux allows by default. The following commands will increase the permitted buffer sizes on Linux:

sysctl net.core.wmem_max=16777216
sysctl net.core.rmem_max=16777216

Note that these commands are not persistent across reboots, and the settings need to be stored in /etc/sysctl.conf or /etc/sysctl.d.

Installing spead2 for Python

The only Python dependency is numpy.

The test suite has additional dependencies; refer to if you are developing spead2.

There are two ways to install spead2 for Python: compiling from source and installing a binary wheel.

Installing a binary wheel

As from version 1.12, binary wheels are provided on PyPI for x86-64 Linux systems. These support all the optional features, and it is now the recommended installation method as it does not depend on a compiler, development libraries etc. The wheels use the “manylinux2010” tag, which requires at least pip 19.0 to install.

Provided your system meets these requirements, just run:

pip install spead2

Python install from source

Installing from source requires a modern C++ compiler supporting C++11 (GCC 4.8+ or Clang 3.5+, although only GCC 5.4 and Clang 3.8 are tested and support for older compilers may be dropped) as well as Boost (including compiled libraries) and the Python development headers. At the moment only GNU/Linux and OS X get tested but other POSIX-like systems should work too. There are no plans to support Windows.

Installation works with standard Python installation methods.

Installing spead2 for C++

spead2 requires a modern C++ compiler supporting C++11 (see above for supported compilers) as well as Boost (including compiled libraries). At the moment only GNU/Linux and OS X get tested but other POSIX-like systems should work too. There are no plans to support Windows.

The C++ API uses the standard autoconf installation flow i.e.:

./configure [options]
make install

For generic help with configuration, see INSTALL in the top level of the source distribution. Optional features are autodetected by default, but can be disabled by passing options to configure (run ./configure -h to see a list of options).

One option that may squeeze out a very small amount of extra performance is --enable-lto to enable link-time optimization. Up to version 1.2.0 this was enabled by default, but it has been disabled because it often needs other compiler or OS-specific configuration to make it work. For GCC, typical usage is

./configure --enable-lto AR=gcc-ar RANLIB=gcc-ranlib

The installation will install some benchmark tools, a static library, and the header files. At the moment there is no intention to create a shared library, because the ABI is not stable.