How would you make this switch statement as fast as possible?

Question

2009-12-04 UPDATE: For profiling results on a number of the suggestions posted here, see below!

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The Question

Consider the following very

Answer 1

Messy but using a combination of nested ifs and hard coding might just beat the optimiser:-

   if (ActivCode < "N") {
         // "" to "MW"
         if (ActiveCode < "BT") {
            // "" to "B"
            if (ActiveCode < "B") {
                // "" or "A"
                if (ActiveCode < "A") {
                      // must be ""
                     retrun MarketDataExchange.NBBO;
                } else {
                     // must be "A"
                    return MarketDataExchange.AMEX;
                }
            } else {
                // must be "B"
                return MarketDataExchange.BSE;
            }
         } else {
            // "BT" to "MW"
            if (ActiveCode < "MW") {
                // "BT" or "C"
                if (ActiveCode < "C") {
                      // must be "BT"
                     retrun MarketDataExchange.NBBO;
                } else {
                     // must be "C"
                    return MarketDataExchange.NSE;
                }
            } else {
            // must be "MV"
                return MarketDataExchange.CHX;
            }
         }
    } else {
        // "N" TO "Y"
         if (ActiveCode < "QD") {
            // "N" to "Q"
            if (ActiveCode < "Q") {
                // "N" or "PA"
                if (ActiveCode < "PA") {
                      // must be "N"
                     retrun MarketDataExchange.NYSE;
                } else {
                     // must be "PA"
                    return MarketDataExchange.ARCA;
                }
            } else {
                // must be "Q"
                return MarketDataExchange.NASDAQ;
            }
         } else {
            // "QD" to "Y"
            if (ActiveCode < "X") {
                // "QD" or "W"
                if (ActiveCode < "W") {
                      // must be "QD"
                     retrun MarketDataExchange.NASDAQ_ADF;
                } else {
                     // must be "W"
                    return MarketDataExchange.CBOE;
                }
            } else {
            // "X" or "Y"
                if (ActiveCode < "Y") {
                      // must be "X"
                     retrun MarketDataExchange.PHLX;
                } else {
                     // must be "Y"
                    return MarketDataExchange.DIRECTEDGE;
                }
            }
         }
    }

This gets the right function with three or four compares. I wouldnt even think of doing this for real unless your piece of code is expected to run several times a second!

You further otimise it so that only single character compares occurred. e.g. replace '< "BT" ' with '>= "B" ' -- ever so slightly faster and even less readable!