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[delaunay] Qhull trace options (T)

Copyright © 1995, 1997 The Geometry Center, Minneapolis MN


SynopsisMainOutputFormatsGeomviewPrintQhullPrecisionTrace

»Trace options

Tv
verify result: structure, convexity, and point inclusion
Tc
check frequently during execution
Ts
print statistics
Tz
send all output to stdout
TFn
report summary whenever n or more facets created
TV-n
stop qhull before adding point n
TCn
stop qhull after building cone for point n
TVn
stop qhull after adding point n
T4
trace at level n, 4=all, 5=mem/gauss, -1= events
TPn
turn on tracing when point n added to hull
TMn
turn on tracing at merge n
TWn
trace merge facets when width > n

»Tv - verify result: structure, convexity, and point inclusion

Option 'Tv' checks the topological structure, convexity, and point inclusion. If precision problems occurred, facet convexity is tested whether or not 'Tv' is selected. Option 'Tv' does not check point inclusion if forcing output with 'Po', or if 'Q5' is set.

The convex hull of a set of points is the smallest polytope that includes the points. Option 'Tv' tests point inclusion. Qhull verifies that all points are below all outer planes (facet->maxoutside). Point inclusion is exhaustive if merging or if the facet-point product is small enough; otherwise Qhull verifies each point with a directed search (qh_findbest). To force an exhaustive test when using option 'C-0' (default), use 'C-1e-30' instead.

Point inclusion testing occurs after producing output. It prints a message to stderr unless option 'Pp' is used. This allows the user to interrupt Qhull without changing the output.

»Tc - check frequently during execution

Qhull includes frequent checks of its data structures. Option 'Tc' will catch most inconsistency errors. It is slow and should not be used for production runs. Option 'Tv' performs the same checks after the hull is constructed.

»Ts - print statistics

Option 'Ts' collects statistics and prints them to stderr. For Delaunay triangulations, the angle statistics are restricted to the lower or upper envelope.

»Tz - send all output to stdout

Redirect stderr to stdout.

»TFn - report summary whenever n or more facets created

Option 'TFn' reports progress whenever more than n facets are created. The test occurs just before adding a new point to the hull. During post-merging, 'TFn' reports progress after more than n/2 merges.

»TV-n - stop qhull before adding point n

Qhull adds one point at a time to the convex hull. See how Qhull adds a point. Option 'TV-n' stops Qhull just before adding a new point. Output shows the hull at this time.

»TCn - stop qhull after building cone for point n

Qhull builds a cone from the point to its horizon facets. Option 'TCn' stops Qhull just after building the cone. The output for 'f' includes the cone and the old hull.'.

»TVn - stop qhull after adding point n

Option 'TVn' stops Qhull after it has added point n. Output shows the hull at this time.

»Tn - trace at level n

Qhull includes full execution tracing. 'T-1' traces events. 'T1' traces the overall execution of the program. 'T2' and 'T3' trace overall execution and geometric and topological events. 'T4' traces the algorithm. 'T5' includes information about memory allocation and Gaussian elimination. 'T1' is useful for logging progress of Qhull in high dimensions.

Option 'Tn' can produce large amounts of output. Use options 'TPn' and 'TMn' to selectively turn on tracing. Since all errors report the last processed point, option 'TPn' is particularly useful.

»TPn - turn on tracing when point n added to hull

This reduces the output size when tracing. It is the normal method to determine the cause of a Qhull error. All Qhull errors report the last point added.

»TMn - turn on tracing at merge n

Turn on tracing at n'th merge.

»TWn - trace merge facets when width > n

Along with TMn, this option allows the user to determine the cause of a wide merge.


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Created: Sept. 25, 1995 --- Last modified: see top