JTools Table of Contents
Project Location: \JTools_Level2Viewer
The Level 2 Viewer sorts and displays NASDAQ Level 2 Market Maker data. The application demonstrates several key concepts related to both NxCore/GUI systems intended for real world use, including:
- How to use MMQuotes, ExgQuotes, StateMMQuotes and StateExgQuotes in NxCore.
- How to avoid using costly string compares when processing data by making use of each market makers string pointer.
- How to keep the entire application integer based (only converting to floating point when a GUI element is actually populated).
- How to process data rapidly onto the GUI (even when running historical tapes at full blast) without losing responsiveness.
The fields in the Level 2 Viewer include:
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Symbol Convention:
Since this application is specific to equities, you may enter symbols with or without the lowercase 'e'. Examples would be "eIBM" (the standard NxCore convention for equities) or just "IBM".
Furthermore, because a symbol may be duplicated on more than one listing exchange. For instance GE is listed on both the NYSE and Canadian exchange, and represent different companies. While the symbols default to the US symbols, it is possible to specify the listing exchange the symbol. As an example of how to specify the listing exchange in the symbol:
- GE or GE:3 - General Electric on the NYSE exchange (exchange # 3).
- GE:19 - Granville Pacific Capital Corp on the CDNX exchange (exchange #19).
The exchange designators correspond to the default NxCore exchange codes found here: NxCore Exchange Codes
You may enter a new symbol at any time. Simply type in the symbol and press the ENTER key. If the symbol is valid, the display will clear and immediately populate with with the current quotes from each exchange and the most recent price information (through the use ofNxCoreStateGetMMQuotes, NxCoreStateGetExgQuotes and NxCoreStateGetLastTrade). After that the stats and level 2 lists are populated with all streaming trade and quote messages (NxMSG_TRADE, NxMSG_MMQUOTE and NxMSG_EXGQUOTE).
If the symbol entered is not valid, a "Symbol Not Found" message is displayed in the Name field.
You can cancel listening to a symbol by simply clearing the symbol and pressing the ENTER key.
If you have not started NxCore prior to entering a symbol then NxCore will be started when you press ENTER. When doing this, it may take a couple seconds for the symbol's name to appear as NxCore has just started and the category information (with company names) does not become available for the first few minutes of the tape. When entering symbols after the tape has been started all information is delivered immediately.
One further caveat - if you have started NxCore using an NxCore State File (as opposed to an NxCore historical tape) the company names will most likely not be available. This is because the state file will (most likely) be from a timeframe beyond the Category 4 messages (which occur in the first few minutes of the tape) and as such, they are not available at the point where the state file begins to process the tape. No other aspect of the application is effected when running from state files.
Performance:
While the application was written with the intention of viewing equities in real time, you can also blast through a historical tape as fast as possible and the application will remain snappy and responsive. This is accomplished through a variety of mechanisms:
- The use of the userdata1 field contained in each NxCore symbol string which
is unique (and remains static) to all issues in the system. By using this field
to designate when a symbol has interest set, all string compares can be
eliminated during processing of the stream. It cannot be over emphasized how
much processing time is saved when eliminating string compares in a
whole-market feed.
- The use of the Market Maker string pointers to eliminate string comparisons
during processing of the stream. Again, it cannot be over emphasized how much
processing time is saved when eliminating string compares in a whole-market
feed.
- The application was intended for a human to view. While quotes may change
1000's of times a second, a human can simply not process every change in that
time frame. The human brain will see a seamless display if the display is
updating approx. 24 times a second. Now, updating any GUI element is about the
most processing intensive item you can do in any one single line of code. So,
if the human brain cannot distinguish detail at 24 times a second, why update
the display any more than that? The Quote Montage display list in this
application is updated from a timer which remains constant as the application
runs. The timer is fired every 40 milliseconds, which equates to 25 updates per
second. Additionally, any item that has not changed during a refresh cycle is
not updated. This does mean keeping track of the values set and doing simple
compares at every refresh, but doing those compares is far less expensive than
a GUI field update.
- All values are stored, used and calculated using the raw NxCore price integer (as opposed to converting every price field to a double for each message). The price type of each item is also stored and the only time a price is converted into a double is when it is actually used to update a GUI fields and be displayed to the user.
JTools Table of Contents