Greetings,
I've just finished a "dealer locator" app that provides a list of store
addresses within X miles to given zip code. It's basically that "show me
the closest locations to me" feature that every site seems to have now.
While it was not the big of a deal to develop, I'm running into some
performance issues, and they seem to revolve around Witango's ability to
perform complex triginomic calculations. Here's the code that seems to be
slowing it down:
<@ROWS ARRAY="local$matches">
<@! define variables >
<@ASSIGN NAME="lat2" SCOPE="local" VALUE='<@COL 2>'>
<@ASSIGN NAME="long2" SCOPE="local" VALUE='<@COL 3>'>
<@! calc distance in kilometers >
<@ASSIGN NAME="x" SCOPE="local" VALUE='<@CALC EXPR="(sin(@@local$lat1 *
@@local$pi / 180) * sin(@@local$lat2 * @@local$pi / 180) + cos(@@local$lat1
* @@local$pi / 180) * cos(@@local$lat2 * @@local$pi / 180) *
cos(abs((@@local$long2 * @@local$pi / 180)-(@@local$long1 * @@local$pi /
180))))">'>
<@ASSIGN NAME="x" SCOPE="local" VALUE='<@CALC
EXPR="atan((sqrt(1-(@@local$x*@@local$x)))/@@local$x)">'>
<@ASSIGN NAME="dist_km" SCOPE="local" VALUE='<@CALC EXPR="1.852 * 60.0 *
((@@local$x/@@local$pi)*180)">'>
<@! convert distance to miles >
<@ASSIGN NAME="dist_mi" SCOPE="local" VALUE='<@CALC EXPR="@@local$dist_km /
1.609344">'>
<@! add row to array with distances >
<@ASSIGN NAME="row_str" SCOPE="local" VALUE='<@COL 1>,<@COL 2>,<@COL
3>,@@local$dist_mi,<@OMIT STR="<@COL 4>" CHARS=",">,<@OMIT STR="<@COL 5>"
CHARS=",">,<@OMIT STR="<@COL 6>" CHARS=",">,<@COL 7>,<@COL 8>'>
<@ADDROWS ARRAY="local$matches2" VALUE="<@ARRAY ROWS='1' COLS='9'
VALUE='@@local$row_str'>">
</@ROWS>
The "matches" array is generated by finding all locations that fit within a
pair of lattitude and logitude corrdinates that were calculated in a
previous step. Basically, the user enteres a zip code and a desired
distance from that zip code and it finds all addresses within that area,
leaving you with the "matches" array. The code above then takes that array
and determines the exact distance from the target zip code so it can sort
the list accordingly.
This array can contain anywhere from just a few addresses to thousands. Any
thing under about 100 matches it can process in about 3 seconds or less.
More than about 100, and the user is twiddling their thumbs in wait. Here's
some times I've logged with the assistance of the <@TIMER> tag.
MATCHES TIME(MS)
58 1166
79 2033
148 6950
206 12700
291 23617
320 28450
660 113733
Server Specs: Dual 500 PIII, 500 MB Ram, running Win NT 4.0
Does this seem like an excessivly long time to do this kind of math, or is
it just me? Would I be better off writing this particular bit of code so
that SQL does the math?
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