[xquery-talk] Matrix Multiplication (JSONiq)

[Hermann Stamm-Wilbrandt]

Last Sylvester there was a thread on Matrix Multiplication in XQuery:
http://markmail.org/message/7q7qnbbnjo7cljzv?q=list:com.x-query.talk+matrix
+multiplication

The biggest problem identified was that XQuery does not allow for efficient
representation of 2+dimensional arrays.

JSON does provide 2+dimensional arrays for free.

I did not measure performance yet, but this JSONiq script looks very
similar to what would be done in C:
http://try.zorba.io/queries/xquery/jFd3Q8f82HuZGzcYDzQpdN4SdfY=

declare variable $A := [
  [1,2],
  [3,4],
  [5,6],
  [7,8]
];
declare variable $B := [
  [1,2,3],
  [4,5,6]
];

[
  for $i in 1 to count(jn:members($A)) return
  [
    for $k in 1 to count(jn:members($B(1))) return
      fn:sum(
        for $j in 1 to count(jn:members($B)) return
          $A($i)($j) * $B($j)($k)
      )
  ]
]


And much simpler than in XSLT:
http://rosettacode.org/wiki/Matrix_multiplication#XSLT_1.0:


Mit besten Gruessen / Best wishes,

Hermann Stamm-Wilbrandt
Level 3 support for XML Compiler team and Fixpack team lead
WebSphere DataPower SOA Appliances
https://www.ibm.com/developerworks/mydeveloperworks/blogs/HermannSW/
https://twitter.com/HermannSW/
http://stamm-wilbrandt.de/GraphvizFiddle/
----------------------------------------------------------------------
IBM Deutschland Research & Development GmbH
Vorsitzende des Aufsichtsrats: Martina Koederitz
Geschaeftsfuehrung: Dirk Wittkopp
Sitz der Gesellschaft: Boeblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294