Users' Knowledge Base

_Trace() Statements

If you use many debug statements, you can speed up your code by using conditional debug code (shown below), and you can control debug output with a ParamToggle() using _TRACE statements:

DBVOn = ParamToggle("DebugView","OFF|ON", 0);
if( DBVOn ) _TRACE( "# "+ YourDebuggingText );

To keep your main code short and simple, you can also wrap the _TRACE() statement into a similarly named custom TRACE() function that you would call instead of the _TRACE() (note the “_” has been removed):

function TRACE( DBVString )
{
global DBVOn;
if( DBVOn ) _TRACE( "# "+ YourDebuggingText );
}

You may find it handy to keep the debugging code in the system until it is fully functional or, if the minor speed penalty is no problem, turn it off and leave it there permanently. You can also create a custom library of debugging functions and make them available for use at any time by including them in your code using a #Include statement, which are stored in the folder C:\Program Files\AmiBroker\Formulas\Include. This path is defined in Tools/Preferences/AFL/Standard Include Path/Formulas/Include.

Logging

Using too many _TRACE() statements or allowing the DebugView output file grow too large will slow down AFL execution. To prevent the file from growing too large, it is a good idea to add a manual clear function so that you can clear it occasionally:

ClearDBV = ParamTrigger("Clear DebugView","CLEAR DBV");
if( ClearDBV ) _TRACE("# DBGVIEWCLEAR");


You can further reduce overhead by controlling the amount of logging detail. You do this by using a ParamList() whereby you can set the required logging level. For example, you might want to control debug statements inside and outside a loop separately. Below is a simple example that scans a Watchlist from your Indicator once every 5-seconds:

RequestTimedRefresh(5);
ClearDBV = ParamTrigger("Clear DebugView","CLEAR DBV");
if( ClearDBV ) _TRACE("# DBGVIEWCLEAR");
DBVLevel = ParamList("DBV Logging Level","NO LOGGING|SCAN TIME ONLY|SCAN TIME AND LOOP",0 );
DBVL1 = DBVLevel == "SCAN TIME ONLY";
DBVL2 = DBVLevel == "SCAN TIME AND LOOP";
scan = Status("redrawaction");
if( Scan )
{
if( DBVL1 OR DBVL2) _TRACE( "#1 Scan Triggered at "+Now(0) );
TickerList = ParamStr("Ticker List","AAPL,BRCM,CSCO,MXIM,GOOG");
for( i = 0; ( Ticker = StrExtract( TickerList, i ) ) != ""; i++ )
{
TickerPrice = GetRTDataForeign("Last",Ticker);
if( DBVL2 )
{
_TRACE( "#2 Scanning "+Ticker+", "+NumToStr(TickerPrice,1.2));
}
}
if( DBVL2 ) _TRACE("#"); // Skip a line in the log
}

Edited by Al Venosa

Filed by Herman at 9:22 am under Debugging AFL
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