private Map<String,Double> rankingExpressionParserParse(String values, Map<String,Double> map) {
        return new DoubleMapParser().parse(values,map);
    }
A benchmark of map parsing.
Expected time on Jon's mac: 200 microseconds per 1k size map.

@author bratseth
vespajlib/src/test/java/com/yahoo/text/MapParserMicroBenchmark.java