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GNU Go Documentation

4.6.2 Tracing

A function gprintf() is provided. It is a cut-down printf, supporting only %c, %d, %s, and without field widths, etc. It does, however, add some useful facilities:

• %m

  Takes two parameters, and displays a formatted board co-ordinate.

• indentation

  Trace messages are automatically indented to reflect the current stack depth, so it is clear during read-ahead when it puts a move down or takes one back.

• "outdent"

  format string suppresses the indentation.

A variant mprintf sends output to stderr. Normally gprintf() is wrapped in one of the following:

TRACE(fmt, ...):

Print the message if the 'verbose' variable > 0. (verbose is set by -t on the command line)

DEBUG(flags, fmt, ...):

While TRACE is intended to afford an overview of what GNU Go is considering, DEBUG allows occasional in depth study of a module, usually needed when something goes wrong. flags is one of the DEBUG_* symbols in `engine/gnugo.h'. The DEBUG macro tests to see if that bit is set in the debug variable, and prints the message if it is. The debug variable is set using the -d command-line option.

The variable verbose controls the tracing. It can equal 0 (no trace), 1, 2, 3 or 4 for increasing levels of tracing. You can set the trace level at the command line by `-t' for verbose=1, `-t -t' for verbose=2, etc. But in practice if you want more verbose tracing than level 1 it is better to use gdb to reach the point where you want the tracing; you will often find that the variable verbose has been temporarily set to zero and you can use the gdb command set var verbose=1 to turn the tracing back on.