I doubt you'll find much improvement on this.
You could cut out the call on number() and rely on implicit conversion, but I
doubt it makes any difference.
You could factor out the expressions ($A/col) and ($B/col) into variables
declared outside the loop, which might make a difference: finding the Nth child
of an element might well take time proportional to N, whereas finding the Nth
item in a sequence held in a variable is likely to be constant time. But it
depends on the processor, of course. Measgre it and let us know the results.
A significant part of the cost is likely to be string-to-double conversion, and
there's no way of avoiding that.
Michael Kay
Saxonica
On 9 May 2020, at 12:59, Costello, Roger L. costello(_at_)mitre(_dot_)org
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:
Hi Folks,
I need a super-efficient way to compute the sum of A[i] * B[i] for i=1 to n.
For example, suppose A is this:
<row>
<col>0.9</col>
<col>0.3</col>
</row>
and B is this:
<row>
<col>0.2</col>
<col>0.8</col>
</row>
I want to compute:
(0.9 * 0.2) + (0.3 * 0.8)
Here's one way to do it:
sum(for $i in 1 to count($A/col) return number($A/col[$i]) *
number($B/col[$i]))
I suspect that is not the most efficient approach.
What is the most efficient approach? I will be doing hundreds of thousands of
these computations, so I want to use the most efficient approach.
/Roger
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