to be or not to be ?

#+TITLE: libpsyc Performance Benchmarks In this document we present the results of performance benchmarks of libpsyc compared with libjson-glib and libxml2. * Procedure We'll use typical messages from the XMPP ("stanzas" in Jabber lingo) and compare them with equivalent JSON encodings, verbose and compact PSYC formats. In some cases we will additionally compare PSYC packets to a more efficient XML encoding based on PSYC methods, to have a more accurate comparison of the actual PSYC and XML syntaxes, rather than the protocol structures of PSYC and XMPP. * The Benchmarks ** A presence packet Since presence packets are by far the dominant messaging content in the XMPP network, we'll start with one of them. Here's an example from paragraph 4.4.2 of RFC 6121. #+BEGIN_SRC xml :tangle packets/presence.xml away #+END_SRC And here's the same information in a JSON rendition: #+BEGIN_SRC js :tangle packets/presence.json ["presence",{"from":"juliet@example.com/balcony","to":"benvolio@example.net"},{"show":"away"}] #+END_SRC Here's the equivalent PSYC packet in verbose form (since it is a multicast, the single recipients do not need to be mentioned): #+BEGIN_SRC psyc :tangle packets/presence.psyc :_context psyc://example.com/~juliet =_degree_availability 4 _notice_presence | #+END_SRC And the same in compact form: #+BEGIN_SRC psyc :c psyc://example.com/~juliet =da 4 np | #+END_SRC ** An average chat message XML: #+BEGIN_SRC xml :tangle packets/chat_msg.xml Art thou not Romeo, and a Montague? #+END_SRC PSYC: #+BEGIN_SRC psyc :tangle packets/chat_msg.psyc :_source psyc://example.com/~juliet :_target psyc://example.net/~romeo _message_private Art thou not Romeo, and a Montague? | #+END_SRC ** A new status updated activity Example taken from http://onesocialweb.org/spec/1.0/osw-activities.html You could call this XML namespace hell: #+BEGIN_SRC xml :tangle packets/activity.xml to be or not to be ? http://activitystrea.ms/schema/1.0/post

http://onesocialweb.org/spec/1.0/object/status

to be or not to be ?

http://onesocialweb.org/spec/1.0/acl/action/view

#+END_SRC http://activitystrea.ms/head/json-activity.html proposes a JSON encoding of this. We'll have to add a routing header to it. #+BEGIN_SRC js :tangle packets/activity.json ["activity",{"from":"hamlet@denmark.lit/snsclient"},{"verb":"post", "title":"to be or not to be ?","object":{"type":"status", "content":"to be or not to be ?","contentType":"text/plain"}}] #+END_SRC http://about.psyc.eu/Activity suggests a PSYC mapping for activity streams. Should a "status post" be considered equivalent to a presence description announcement or just a message in the "microblogging" channel? We'll use the latter here: #+BEGIN_SRC psyc :tangle packets/activity.psyc :_context psyc://denmark.lit/~hamlet#_follow :_subject to be or not to be ? :_type_content text/plain _message to be or not to be ? | #+END_SRC ** A message with JSON-unfriendly characters #+BEGIN_SRC xml :tangle packets/json-unfriendly.xml "Neither, fair saint, if either thee dislike.", he said. And the rest is history. #+END_SRC ** A message with XML-unfriendly characters #+BEGIN_SRC xml :tangle packets/xml-unfriendly.xml Wherefore art thou, Romeo? PročeŽ jsi ty, Romeo? #+END_SRC ** A message with PSYC-unfriendly strings #+BEGIN_SRC xml :tangle packets/psyc-unfriendly.xml I implore you with a pointless newline in a header variable Wherefore art thou, Romeo? | And for practicing purposes we added a PSYC packet delimiter. #+END_SRC ** A packet containing a JPEG photograph ... TBD ... ** A random data structure In this test we'll not consider XMPP at all and simply compare the efficiency of the three syntaxes at serializing a typical user data base storage information. We'll again start with XML: #+BEGIN_SRC xml :tangle packets/user_profile.xml Silvio Berlusconi Premier I

Via del Colosseo, 1 00100 Roma

http://example.org #+END_SRC In JSON this would look like this: #+BEGIN_SRC js :tangle packets/user_profile.json ["UserProfile",{"Name":"Silvio Berlusconi","JobTitle":"Premier","Country":"I","Address": {"Street":"Via del Colosseo, 1","PostalCode":"00100","City":"Roma"},"Page":"http://example.org"}] #+END_SRC Here's a way to model this in PSYC: #+BEGIN_SRC psyc :tangle packets/user_profile.psyc :_name Silvio Berlusconi :_title_job Premier :_country I :_address_street Via del Colosseo, 1 :_address_code_postal 00100 :_address_city Roma :_page http://example.org _profile_user | #+END_SRC * Conclusions ... TBD ... * Criticism Are we comparing apples and oranges? Yes and no, depends on what you need. XML is a syntax best suited for complex structured data in well-defined formats - especially good for text mark-up. JSON is a syntax intended to hold arbitrarily structured data suitable for immediate inclusion in javascript source codes. The PSYC syntax is an evolved derivate of RFC 822, the syntax used by HTTP and E-Mail, and is therefore limited in the kind and depth of data structures that can be represented with it, but in exchange it is highly performant at doing just that. So it is up to you to find out which of the three formats fulfils your requirements the best. We use PSYC for the majority of messaging where JSON and XMPP aren't efficient and opaque enough, but we employ XML and JSON as payloads within PSYC for data that doesn't fit the PSYC model. For some reason all three formats are being used for messaging, although only PSYC was actually designed for that purpose. * Caveats In every case we'll compare performance of parsing and re-rendering these messages, but consider also that the applicative processing of an XML DOM tree is more complicated than just accessing certain elements in a JSON data structure or PSYC variable mapping. For a speed check in real world conditions which also consider the complexity of processing incoming messages we should compare the performance of a chat client using the two protocols, for instance by using libpurple with XMPP and PSYC accounts. To this purpose we first need to integrate libpsyc into libpurple. * Futures After a month of development libpsyc is already performing pretty well, but we presume various optimizations, like rewriting parts in assembler, are possible.