Author: damien Date: Fri Jun 6 12:24:53 2008 New Revision: 664091 URL: http://svn.apache.org/viewvc?rev=664091&view=rev Log: Added comments and clarity to the reduce/combine test Modified: incubator/couchdb/trunk/share/www/script/couch_tests.js Modified: incubator/couchdb/trunk/share/www/script/couch_tests.js URL: http://svn.apache.org/viewvc/incubator/couchdb/trunk/share/www/script/couch_tests.js?rev=664091&r1=664090&r2=664091&view=diff ============================================================================== --- incubator/couchdb/trunk/share/www/script/couch_tests.js [utf-8] (original) +++ incubator/couchdb/trunk/share/www/script/couch_tests.js [utf-8] Fri Jun 6 12:24:53 2008 @@ -352,14 +352,16 @@ var map = function (doc) {emit(null, doc.val)}; var reduceCombine = function (keys, values, combine) { - // this computes the standard deviation - + // This computes the standard deviation of the mapped results var stdDeviation=0; var count=0; var total=0; var sqrTotal=0; if (combine) { + // This is the combine phase, we are re-reducing previosuly returned + // reduce values. + for(var i in values) { count = count + values[i].count; total = total + values[i].total; @@ -367,11 +369,10 @@ } var variance = (sqrTotal - ((total * total)/count)) / count; stdDeviation = Math.sqrt(variance); - - return {"stdDeviation":stdDeviation,"count":count, - "total":total,"sqrTotal":sqrTotal}; } else { + // This is the reduce phase, we are reducing over emitted values from + // the map functions. for(var i in values) { total = total + values[i] sqrTotal = sqrTotal + (values[i] * values[i]) @@ -380,13 +381,15 @@ var variance = (sqrTotal - ((total * total)/count)) / count; stdDeviation = Math.sqrt(variance); } - + + // the reduce results. It contains enough information to compute + // further reduce results, and the final output values. return {"stdDeviation":stdDeviation,"count":count, "total":total,"sqrTotal":sqrTotal}; }; + // Save a bunch a docs. for(var j=0; j < 10; j++) { - // these docs are in the order of the keys collation, for clarity var docs = []; docs.push({val:10}); docs.push({val:20}); @@ -402,8 +405,10 @@ } var results = db.query(map, reduceCombine); - //account for floating point error - T(results.rows[0].value.stdDeviation == 28.722813232690143); + + var difference = results.rows[0].value.stdDeviation - 28.722813232690143; + // account for floating point rounding error + T(Math.abs(difference) < 0.0000000001); },