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user.c
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/*<html><pre> -<a href="qh-user.htm"
>-------------------------------</a><a name="TOP">-</a>
user.c
user redefinable functions
see user2.c for qh_fprintf, qh_malloc, qh_free
see README.txt see COPYING.txt for copyright information.
see libqhull.h for data structures, macros, and user-callable functions.
see user_eg.c, user_eg2.c, and unix.c for examples.
see user.h for user-definable constants
use qh_NOmem in mem.h to turn off memory management
use qh_NOmerge in user.h to turn off facet merging
set qh_KEEPstatistics in user.h to 0 to turn off statistics
This is unsupported software. You're welcome to make changes,
but you're on your own if something goes wrong. Use 'Tc' to
check frequently. Usually qhull will report an error if
a data structure becomes inconsistent. If so, it also reports
the last point added to the hull, e.g., 102. You can then trace
the execution of qhull with "T4P102".
Please report any errors that you fix to qhull@qhull.org
Qhull-template is a template for calling qhull from within your application
if you recompile and load this module, then user.o will not be loaded
from qhull.a
you can add additional quick allocation sizes in qh_user_memsizes
if the other functions here are redefined to not use qh_print...,
then io.o will not be loaded from qhull.a. See user_eg.c for an
example. We recommend keeping io.o for the extra debugging
information it supplies.
*/
#include "qhull_a.h"
#include <stdarg.h>
/*-<a href="qh-user.htm#TOC"
>-------------------------------</a><a name="qhull_template">-</a>
Qhull-template
Template for calling qhull from inside your program
returns:
exit code(see qh_ERR... in libqhull.h)
all memory freed
notes:
This can be called any number of times.
*/
#if 0
{
int dim; /* dimension of points */
int numpoints; /* number of points */
coordT *points; /* array of coordinates for each point */
boolT ismalloc; /* True if qhull should free points in qh_freeqhull() or reallocation */
char flags[]= "qhull Tv"; /* option flags for qhull, see qh_opt.htm */
FILE *outfile= stdout; /* output from qh_produce_output()
use NULL to skip qh_produce_output() */
FILE *errfile= stderr; /* error messages from qhull code */
int exitcode; /* 0 if no error from qhull */
facetT *facet; /* set by FORALLfacets */
int curlong, totlong; /* memory remaining after qh_memfreeshort */
QHULL_LIB_CHECK /* Check for compatible library */
#if qh_QHpointer /* see user.h */
if (qh_qh){ /* should be NULL */
qh_printf_stderr(6238, "Qhull link error. The global variable qh_qh was not initialized\n\
to NULL by global.c. Please compile this program with -Dqh_QHpointer_dllimport\n\
as well as -Dqh_QHpointer, or use libqhullstatic, or use a different tool chain.\n\n");
exit(1);
}
#endif
/* initialize dim, numpoints, points[], ismalloc here */
exitcode= qh_new_qhull(dim, numpoints, points, ismalloc,
flags, outfile, errfile);
if (!exitcode) { /* if no error */
/* 'qh facet_list' contains the convex hull */
FORALLfacets {
/* ... your code ... */
}
}
qh_freeqhull(!qh_ALL);
qh_memfreeshort(&curlong, &totlong);
if (curlong || totlong)
qh_fprintf(errfile, 7068, "qhull internal warning (main): did not free %d bytes of long memory(%d pieces)\n", totlong, curlong);
}
#endif
/*-<a href="qh-user.htm#TOC"
>-------------------------------</a><a name="new_qhull">-</a>
qh_new_qhull( dim, numpoints, points, ismalloc, qhull_cmd, outfile, errfile )
build new qhull data structure and return exitcode (0 if no errors)
if numpoints=0 and points=NULL, initializes qhull
notes:
do not modify points until finished with results.
The qhull data structure contains pointers into the points array.
do not call qhull functions before qh_new_qhull().
The qhull data structure is not initialized until qh_new_qhull().
Default errfile is stderr, outfile may be null
qhull_cmd must start with "qhull "
projects points to a new point array for Delaunay triangulations ('d' and 'v')
transforms points into a new point array for halfspace intersection ('H')
To allow multiple, concurrent calls to qhull()
- set qh_QHpointer in user.h
- use qh_save_qhull and qh_restore_qhull to swap the global data structure between calls.
- use qh_freeqhull(qh_ALL) to free intermediate convex hulls
see:
Qhull-template at the beginning of this file.
An example of using qh_new_qhull is user_eg.c
*/
int qh_new_qhull(int dim, int numpoints, coordT *points, boolT ismalloc,
char *qhull_cmd, FILE *outfile, FILE *errfile) {
int exitcode, hulldim;
boolT new_ismalloc;
static boolT firstcall = True;
coordT *new_points;
if(!errfile){
errfile= stderr;
}
if (firstcall) {
qh_meminit(errfile);
firstcall= False;
}
if (strncmp(qhull_cmd, "qhull ", (size_t)6)) {
qh_fprintf(errfile, 6186, "qhull error (qh_new_qhull): start qhull_cmd argument with \"qhull \"\n");
return qh_ERRinput;
}
qh_initqhull_start(NULL, outfile, errfile);
if(numpoints==0 && points==NULL){
trace1((qh ferr, 1047, "qh_new_qhull: initialize Qhull\n"));
return 0;
}
trace1((qh ferr, 1044, "qh_new_qhull: build new Qhull for %d %d-d points with %s\n", numpoints, dim, qhull_cmd));
exitcode = setjmp(qh errexit);
if (!exitcode)
{
qh NOerrexit = False;
qh_initflags(qhull_cmd);
if (qh DELAUNAY)
qh PROJECTdelaunay= True;
if (qh HALFspace) {
/* points is an array of halfspaces,
the last coordinate of each halfspace is its offset */
hulldim= dim-1;
qh_setfeasible(hulldim);
new_points= qh_sethalfspace_all(dim, numpoints, points, qh feasible_point);
new_ismalloc= True;
if (ismalloc)
qh_free(points);
}else {
hulldim= dim;
new_points= points;
new_ismalloc= ismalloc;
}
qh_init_B(new_points, numpoints, hulldim, new_ismalloc);
qh_qhull();
qh_check_output();
if (outfile) {
qh_produce_output();
}else {
qh_prepare_output();
}
if (qh VERIFYoutput && !qh STOPpoint && !qh STOPcone)
qh_check_points();
}
qh NOerrexit = True;
return exitcode;
} /* new_qhull */
/*-<a href="qh-user.htm#TOC"
>-------------------------------</a><a name="errexit">-</a>
qh_errexit( exitcode, facet, ridge )
report and exit from an error
report facet and ridge if non-NULL
reports useful information such as last point processed
set qh.FORCEoutput to print neighborhood of facet
see:
qh_errexit2() in libqhull.c for printing 2 facets
design:
check for error within error processing
compute qh.hulltime
print facet and ridge (if any)
report commandString, options, qh.furthest_id
print summary and statistics (including precision statistics)
if qh_ERRsingular
print help text for singular data set
exit program via long jump (if defined) or exit()
*/
void qh_errexit(int exitcode, facetT *facet, ridgeT *ridge) {
if (qh ERREXITcalled) {
qh_fprintf(qh ferr, 8126, "\nqhull error while processing previous error. Exit program\n");
qh_exit(qh_ERRqhull);
}
qh ERREXITcalled= True;
if (!qh QHULLfinished)
qh hulltime= qh_CPUclock - qh hulltime;
qh_errprint("ERRONEOUS", facet, NULL, ridge, NULL);
qh_fprintf(qh ferr, 8127, "\nWhile executing: %s | %s\n", qh rbox_command, qh qhull_command);
qh_fprintf(qh ferr, 8128, "Options selected for Qhull %s:\n%s\n", qh_version, qh qhull_options);
if (qh furthest_id >= 0) {
qh_fprintf(qh ferr, 8129, "Last point added to hull was p%d.", qh furthest_id);
if (zzval_(Ztotmerge))
qh_fprintf(qh ferr, 8130, " Last merge was #%d.", zzval_(Ztotmerge));
if (qh QHULLfinished)
qh_fprintf(qh ferr, 8131, "\nQhull has finished constructing the hull.");
else if (qh POSTmerging)
qh_fprintf(qh ferr, 8132, "\nQhull has started post-merging.");
qh_fprintf(qh ferr, 8133, "\n");
}
if (qh FORCEoutput && (qh QHULLfinished || (!facet && !ridge)))
qh_produce_output();
else if (exitcode != qh_ERRinput) {
if (exitcode != qh_ERRsingular && zzval_(Zsetplane) > qh hull_dim+1) {
qh_fprintf(qh ferr, 8134, "\nAt error exit:\n");
qh_printsummary(qh ferr);
if (qh PRINTstatistics) {
qh_collectstatistics();
qh_printstatistics(qh ferr, "at error exit");
qh_memstatistics(qh ferr);
}
}
if (qh PRINTprecision)
qh_printstats(qh ferr, qhstat precision, NULL);
}
if (!exitcode)
exitcode= qh_ERRqhull;
else if (exitcode == qh_ERRsingular)
qh_printhelp_singular(qh ferr);
else if (exitcode == qh_ERRprec && !qh PREmerge)
qh_printhelp_degenerate(qh ferr);
if (qh NOerrexit) {
qh_fprintf(qh ferr, 6187, "qhull error while ending program, or qh->NOerrexit not cleared after setjmp(). Exit program with error.\n");
qh_exit(qh_ERRqhull);
}
qh ERREXITcalled= False;
qh NOerrexit= True;
qh ALLOWrestart= False; /* longjmp will undo qh_build_withrestart */
longjmp(qh errexit, exitcode);
} /* errexit */
/*-<a href="qh-user.htm#TOC"
>-------------------------------</a><a name="errprint">-</a>
qh_errprint( fp, string, atfacet, otherfacet, atridge, atvertex )
prints out the information of facets and ridges to fp
also prints neighbors and geomview output
notes:
except for string, any parameter may be NULL
*/
void qh_errprint(const char *string, facetT *atfacet, facetT *otherfacet, ridgeT *atridge, vertexT *atvertex) {
int i;
if (atfacet) {
qh_fprintf(qh ferr, 8135, "%s FACET:\n", string);
qh_printfacet(qh ferr, atfacet);
}
if (otherfacet) {
qh_fprintf(qh ferr, 8136, "%s OTHER FACET:\n", string);
qh_printfacet(qh ferr, otherfacet);
}
if (atridge) {
qh_fprintf(qh ferr, 8137, "%s RIDGE:\n", string);
qh_printridge(qh ferr, atridge);
if (atridge->top && atridge->top != atfacet && atridge->top != otherfacet)
qh_printfacet(qh ferr, atridge->top);
if (atridge->bottom
&& atridge->bottom != atfacet && atridge->bottom != otherfacet)
qh_printfacet(qh ferr, atridge->bottom);
if (!atfacet)
atfacet= atridge->top;
if (!otherfacet)
otherfacet= otherfacet_(atridge, atfacet);
}
if (atvertex) {
qh_fprintf(qh ferr, 8138, "%s VERTEX:\n", string);
qh_printvertex(qh ferr, atvertex);
}
if (qh fout && qh FORCEoutput && atfacet && !qh QHULLfinished && !qh IStracing) {
qh_fprintf(qh ferr, 8139, "ERRONEOUS and NEIGHBORING FACETS to output\n");
for (i=0; i < qh_PRINTEND; i++) /* use fout for geomview output */
qh_printneighborhood(qh fout, qh PRINTout[i], atfacet, otherfacet,
!qh_ALL);
}
} /* errprint */
/*-<a href="qh-user.htm#TOC"
>-------------------------------</a><a name="printfacetlist">-</a>
qh_printfacetlist( fp, facetlist, facets, printall )
print all fields for a facet list and/or set of facets to fp
if !printall,
only prints good facets
notes:
also prints all vertices
*/
void qh_printfacetlist(facetT *facetlist, setT *facets, boolT printall) {
facetT *facet, **facetp;
qh_printbegin(qh ferr, qh_PRINTfacets, facetlist, facets, printall);
FORALLfacet_(facetlist)
qh_printafacet(qh ferr, qh_PRINTfacets, facet, printall);
FOREACHfacet_(facets)
qh_printafacet(qh ferr, qh_PRINTfacets, facet, printall);
qh_printend(qh ferr, qh_PRINTfacets, facetlist, facets, printall);
} /* printfacetlist */
/*-<a href="qh-io.htm#TOC"
>-------------------------------</a><a name="printhelp_degenerate">-</a>
qh_printhelp_degenerate( fp )
prints descriptive message for precision error
notes:
no message if qh_QUICKhelp
*/
void qh_printhelp_degenerate(FILE *fp) {
if (qh MERGEexact || qh PREmerge || qh JOGGLEmax < REALmax/2)
qh_fprintf(fp, 9368, "\n\
A Qhull error has occurred. Qhull should have corrected the above\n\
precision error. Please send the input and all of the output to\n\
qhull_bug@qhull.org\n");
else if (!qh_QUICKhelp) {
qh_fprintf(fp, 9369, "\n\
Precision problems were detected during construction of the convex hull.\n\
This occurs because convex hull algorithms assume that calculations are\n\
exact, but floating-point arithmetic has roundoff errors.\n\
\n\
To correct for precision problems, do not use 'Q0'. By default, Qhull\n\
selects 'C-0' or 'Qx' and merges non-convex facets. With option 'QJ',\n\
Qhull joggles the input to prevent precision problems. See \"Imprecision\n\
in Qhull\" (qh-impre.htm).\n\
\n\
If you use 'Q0', the output may include\n\
coplanar ridges, concave ridges, and flipped facets. In 4-d and higher,\n\
Qhull may produce a ridge with four neighbors or two facets with the same \n\
vertices. Qhull reports these events when they occur. It stops when a\n\
concave ridge, flipped facet, or duplicate facet occurs.\n");
#if REALfloat
qh_fprintf(fp, 9370, "\
\n\
Qhull is currently using single precision arithmetic. The following\n\
will probably remove the precision problems:\n\
- recompile qhull for realT precision(#define REALfloat 0 in user.h).\n");
#endif
if (qh DELAUNAY && !qh SCALElast && qh MAXabs_coord > 1e4)
qh_fprintf(fp, 9371, "\
\n\
When computing the Delaunay triangulation of coordinates > 1.0,\n\
- use 'Qbb' to scale the last coordinate to [0,m] (max previous coordinate)\n");
if (qh DELAUNAY && !qh ATinfinity)
qh_fprintf(fp, 9372, "\
When computing the Delaunay triangulation:\n\
- use 'Qz' to add a point at-infinity. This reduces precision problems.\n");
qh_fprintf(fp, 9373, "\
\n\
If you need triangular output:\n\
- use option 'Qt' to triangulate the output\n\
- use option 'QJ' to joggle the input points and remove precision errors\n\
- use option 'Ft'. It triangulates non-simplicial facets with added points.\n\
\n\
If you must use 'Q0',\n\
try one or more of the following options. They can not guarantee an output.\n\
- use 'QbB' to scale the input to a cube.\n\
- use 'Po' to produce output and prevent partitioning for flipped facets\n\
- use 'V0' to set min. distance to visible facet as 0 instead of roundoff\n\
- use 'En' to specify a maximum roundoff error less than %2.2g.\n\
- options 'Qf', 'Qbb', and 'QR0' may also help\n",
qh DISTround);
qh_fprintf(fp, 9374, "\
\n\
To guarantee simplicial output:\n\
- use option 'Qt' to triangulate the output\n\
- use option 'QJ' to joggle the input points and remove precision errors\n\
- use option 'Ft' to triangulate the output by adding points\n\
- use exact arithmetic (see \"Imprecision in Qhull\", qh-impre.htm)\n\
");
}
} /* printhelp_degenerate */
/*-<a href="qh-globa.htm#TOC"
>-------------------------------</a><a name="printhelp_narrowhull">-</a>
qh_printhelp_narrowhull( minangle )
Warn about a narrow hull
notes:
Alternatively, reduce qh_WARNnarrow in user.h
*/
void qh_printhelp_narrowhull(FILE *fp, realT minangle) {
qh_fprintf(fp, 9375, "qhull precision warning: \n\
The initial hull is narrow (cosine of min. angle is %.16f).\n\
Is the input lower dimensional (e.g., on a plane in 3-d)? Qhull may\n\
produce a wide facet. Options 'QbB' (scale to unit box) or 'Qbb' (scale\n\
last coordinate) may remove this warning. Use 'Pp' to skip this warning.\n\
See 'Limitations' in qh-impre.htm.\n",
-minangle); /* convert from angle between normals to angle between facets */
} /* printhelp_narrowhull */
/*-<a href="qh-io.htm#TOC"
>-------------------------------</a><a name="printhelp_singular">-</a>
qh_printhelp_singular( fp )
prints descriptive message for singular input
*/
void qh_printhelp_singular(FILE *fp) {
facetT *facet;
vertexT *vertex, **vertexp;
realT min, max, *coord, dist;
int i,k;
qh_fprintf(fp, 9376, "\n\
The input to qhull appears to be less than %d dimensional, or a\n\
computation has overflowed.\n\n\
Qhull could not construct a clearly convex simplex from points:\n",
qh hull_dim);
qh_printvertexlist(fp, "", qh facet_list, NULL, qh_ALL);
if (!qh_QUICKhelp)
qh_fprintf(fp, 9377, "\n\
The center point is coplanar with a facet, or a vertex is coplanar\n\
with a neighboring facet. The maximum round off error for\n\
computing distances is %2.2g. The center point, facets and distances\n\
to the center point are as follows:\n\n", qh DISTround);
qh_printpointid(fp, "center point", qh hull_dim, qh interior_point, qh_IDunknown);
qh_fprintf(fp, 9378, "\n");
FORALLfacets {
qh_fprintf(fp, 9379, "facet");
FOREACHvertex_(facet->vertices)
qh_fprintf(fp, 9380, " p%d", qh_pointid(vertex->point));
zinc_(Zdistio);
qh_distplane(qh interior_point, facet, &dist);
qh_fprintf(fp, 9381, " distance= %4.2g\n", dist);
}
if (!qh_QUICKhelp) {
if (qh HALFspace)
qh_fprintf(fp, 9382, "\n\
These points are the dual of the given halfspaces. They indicate that\n\
the intersection is degenerate.\n");
qh_fprintf(fp, 9383,"\n\
These points either have a maximum or minimum x-coordinate, or\n\
they maximize the determinant for k coordinates. Trial points\n\
are first selected from points that maximize a coordinate.\n");
if (qh hull_dim >= qh_INITIALmax)
qh_fprintf(fp, 9384, "\n\
Because of the high dimension, the min x-coordinate and max-coordinate\n\
points are used if the determinant is non-zero. Option 'Qs' will\n\
do a better, though much slower, job. Instead of 'Qs', you can change\n\
the points by randomly rotating the input with 'QR0'.\n");
}
qh_fprintf(fp, 9385, "\nThe min and max coordinates for each dimension are:\n");
for (k=0; k < qh hull_dim; k++) {
min= REALmax;
max= -REALmin;
for (i=qh num_points, coord= qh first_point+k; i--; coord += qh hull_dim) {
maximize_(max, *coord);
minimize_(min, *coord);
}
qh_fprintf(fp, 9386, " %d: %8.4g %8.4g difference= %4.4g\n", k, min, max, max-min);
}
if (!qh_QUICKhelp) {
qh_fprintf(fp, 9387, "\n\
If the input should be full dimensional, you have several options that\n\
may determine an initial simplex:\n\
- use 'QJ' to joggle the input and make it full dimensional\n\
- use 'QbB' to scale the points to the unit cube\n\
- use 'QR0' to randomly rotate the input for different maximum points\n\
- use 'Qs' to search all points for the initial simplex\n\
- use 'En' to specify a maximum roundoff error less than %2.2g.\n\
- trace execution with 'T3' to see the determinant for each point.\n",
qh DISTround);
#if REALfloat
qh_fprintf(fp, 9388, "\
- recompile qhull for realT precision(#define REALfloat 0 in libqhull.h).\n");
#endif
qh_fprintf(fp, 9389, "\n\
If the input is lower dimensional:\n\
- use 'QJ' to joggle the input and make it full dimensional\n\
- use 'Qbk:0Bk:0' to delete coordinate k from the input. You should\n\
pick the coordinate with the least range. The hull will have the\n\
correct topology.\n\
- determine the flat containing the points, rotate the points\n\
into a coordinate plane, and delete the other coordinates.\n\
- add one or more points to make the input full dimensional.\n\
");
}
} /* printhelp_singular */
/*-<a href="qh-globa.htm#TOC"
>-------------------------------</a><a name="user_memsizes">-</a>
qh_user_memsizes()
allocate up to 10 additional, quick allocation sizes
notes:
increase maximum number of allocations in qh_initqhull_mem()
*/
void qh_user_memsizes(void) {
/* qh_memsize(size); */
} /* user_memsizes */

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