svn:ignore

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@34520 15284696-431f-4ddb-bdfa-cd5b030d7da7

vector/v.delaunay2/main.c

@@ -1,3 +1,19 @@
+/***************************************************************
+ *
+ * MODULE:       v.delaunay
+ *
+ * AUTHOR(S):    Martin Pavlovsky (Paul Kelly mentor)
+ *
+ * PURPOSE:      creates a Delaunay triangulation vector map
+ *
+ * COPYRIGHT:    (C) 2008 by the GRASS Development Team
+ *
+ *               This program is free software under the
+ *               GNU General Public License (>=v2).
+ *               Read the file COPYING that comes with GRASS
+ *               for details.
+ *
+ **************************************************************/
 
 #include <stdio.h>
 #include <stdlib.h>

vector/v.parallel2/Makefile

@@ -0,0 +1,13 @@
+MODULE_TOPDIR = ../..
+
+PGM = v.parallel
+
+LIBES = $(VECTLIB) $(GISLIB)
+DEPENDENCIES= $(VECTDEP) $(GISDEP)
+EXTRA_INC = $(VECT_INC)
+EXTRA_CFLAGS = $(VECT_CFLAGS)
+
+include $(MODULE_TOPDIR)/include/Make/Module.make
+
+default: cmd
+

vector/v.parallel2/dgraph.c

@@ -0,0 +1,454 @@
+#include <stdlib.h>
+#include <grass/Vect.h>
+#include <grass/gis.h>
+#include "dgraph.h"
+#include "e_intersect.h"
+
+#define LENGTH(DX, DY) (sqrt((DX*DX)+(DY*DY)))
+#ifndef MIN
+    #define MIN(X,Y) ((X<Y)?X:Y)
+#endif
+#ifndef MAX
+    #define MAX(X,Y) ((X>Y)?X:Y)
+#endif    
+#define PI M_PI
+
+struct intersection_point {
+    double x;
+    double y;
+    int group; /* IPs with very similar dist will be in the same group */
+};
+
+struct seg_intersection {
+    int with; /* second segment */
+    int ip; /* index of the IP */
+    double dist; /* distance from first point of first segment to intersection point (IP) */
+};
+
+struct seg_intersection_list {
+    int count;
+    int allocated;
+    struct seg_intersection *a;
+};
+
+struct seg_intersections {
+    int ipcount;
+    int ipallocated;
+    struct intersection_point *ip;
+    int ilcount;
+    struct seg_intersection_list *il;
+    int group_count;
+};
+
+struct seg_intersections* create_si_struct(int segments_count) {
+    struct seg_intersections *si;
+    int i;
+    
+    si = G_malloc(sizeof(struct seg_intersections));
+    si->ipcount = 0;
+    si->ipallocated = segments_count + 16;
+    si->ip = G_malloc((si->ipallocated)*sizeof(struct intersection_point));
+    si->ilcount = segments_count;
+    si->il = G_malloc(segments_count*sizeof(struct seg_intersection_list));
+    for (i = 0; i < segments_count; i++) {
+        si->il[i].count = 0;
+        si->il[i].allocated = 0;
+        si->il[i].a = NULL;
+    }
+    
+    return si;
+}
+
+void destroy_si_struct(struct seg_intersections *si) {
+    int i;
+    
+    for (i = 0; i < si->ilcount; i++)
+        G_free(si->il[i].a);
+    G_free(si->il);
+    G_free(si->ip);
+    G_free(si);
+    
+    return;
+}
+
+/* internal use */
+void add_ipoint1(struct seg_intersection_list *il, int with, double dist, int ip) {
+    struct seg_intersection *s;
+
+    if (il->count == il->allocated) {
+        il->allocated += 4;
+        il->a = G_realloc(il->a, (il->allocated)*sizeof(struct seg_intersection));
+    }
+    s = &(il->a[il->count]);
+    s->with = with;
+    s->ip = ip;
+    s->dist = dist;
+    il->count++;
+    
+    return;
+}
+
+/* adds intersection point to the structure */
+void add_ipoint(struct line_pnts *Points, int first_seg, int second_seg, double x, double y, struct seg_intersections *si) {
+    struct intersection_point *t;
+    int ip;
+    
+    G_debug(4, "add_ipoint()");
+    
+    if (si->ipcount == si->ipallocated) {
+        si->ipallocated += 16;
+        si->ip = G_realloc(si->ip, (si->ipallocated)*sizeof(struct intersection_point));
+    }
+    ip = si->ipcount;
+    t = &(si->ip[ip]);
+    t->x = x;
+    t->y = y;
+    t->group = -1;
+    si->ipcount++;
+    
+    add_ipoint1(&(si->il[first_seg]), second_seg, LENGTH((Points->x[first_seg] - x), (Points->y[first_seg] - y)), ip);
+    if (second_seg >= 0)
+        add_ipoint1(&(si->il[second_seg]), first_seg, LENGTH((Points->x[second_seg] - x), (Points->y[second_seg] - y)), ip);
+}
+
+void sort_intersection_list(struct seg_intersection_list *il) {
+    int n, i, j, min;
+    struct seg_intersection t;
+    
+    G_debug(4, "sort_intersection_list()");
+    
+    n = il->count;
+    G_debug(4, "    n=%d", n);
+    for (i = 0; i < n-1; i++) {
+        min = i;
+        for (j = i+1; j < n; j++) {
+            if (il->a[j].dist < il->a[min].dist) {
+                min = j;
+            }
+        }
+        if (min != i) {
+            t = il->a[i];
+            il->a[i] = il->a[min];
+            il->a[min] = t;
+        }
+    }
+    
+    return;
+}
+
+static int compare(const void *a, const void *b)
+{
+    struct intersection_point *aa, *bb;
+    aa = *((struct intersection_point **)a);
+    bb = *((struct intersection_point **)b);
+    
+    if (aa->x < bb->x)
+        return -1;
+    else if (aa->x > bb->x)
+        return 1;
+    else
+        return (aa->y < bb->y)?-1:((aa->y > bb->y)?1:0);
+}        
+
+/* O(Points->n_points) time */
+double get_epsilon(struct line_pnts *Points) {
+    int i, np;
+    double min, t;
+    double *x, *y;
+    
+    np = Points->n_points;
+    x = Points->x;
+    y = Points->y;
+    
+    min = MAX(fabs(x[1]-x[0]), fabs(y[1]-y[0]));
+    for (i = 1; i <= np-2; i++) {
+        t = MAX(fabs(x[i+1]-x[i]), fabs(y[i+1]-y[i]));
+        if ((t > 0) && (t < min)) {
+            min = t;
+        }
+    }
+    
+    /* ??? is 0.001 ok ??? */
+    return min*0.000001;
+}
+
+/* currently O(n*n); future implementation O(nlogn) */
+struct seg_intersections* find_all_intersections(struct line_pnts *Points) {
+    int i, j, np;
+    int group, t;
+    int looped;
+    double EPSILON = 0.00000001;
+    double *x, *y;
+    double x1, y1, x2, y2;
+    int res;
+    /*int res2
+    double x1_, y1_, x2_, y2_, z1_, z2_;*/
+    struct seg_intersections *si;
+    struct seg_intersection_list *il;
+    struct intersection_point **sorted;
+    
+    G_debug(3, "find_all_intersections()");
+    
+    np = Points->n_points;
+    x = Points->x;
+    y = Points->y;
+    
+    si = create_si_struct(np-1);
+    
+    looped = ((x[0] == x[np-1]) && (y[0] == y[np-1]));
+    G_debug(3, "    looped=%d", looped);
+    
+    G_debug(3, "    finding intersections...");
+    for (i = 0; i < np-1; i++) {
+        for (j = i+1; j < np-1; j++) {
+            G_debug(4, "        checking %d-%d %d-%d", i, i+1, j, j+1);
+            /*res = segment_intersection_2d_e(x[i], y[i], x[i+1], y[i+1], x[j], y[j], x[j+1], y[j+1], &x1, &y1, &x2, &y2);*/
+            res = segment_intersection_2d(x[i], y[i], x[i+1], y[i+1], x[j], y[j], x[j+1], y[j+1], &x1, &y1, &x2, &y2);
+/*            res2 = segment_intersection_2d_e(x[i], y[i], x[i+1], y[i+1], x[j], y[j], x[j+1], y[j+1], &x1_, &y1_, &x2_, &y2_);
+            if ((res != res2) || ((res != 0) && (x1!=x1_ || y1!=y1_)) ) {
+                G_debug(0, "exact=%d orig=%d", res, res2);
+                segment_intersection_2d_test(x[i], y[i], x[i+1], y[i+1], x[j], y[j], x[j+1], y[j+1], &x1, &y1, &x2, &y2);
+            }
+*/            
+            G_debug(4, "        intersection type = %d", res);
+            if (res == 1) {
+                add_ipoint(Points, i, j, x1, y1, si);
+            } else if ((res >= 2) && (res <= 5)) {
+                add_ipoint(Points, i, j, x1, y1, si);
+                add_ipoint(Points, i, j, x2, y2, si);
+            }
+        }
+    }
+    if (!looped) {
+        /* these are not really intersection points */
+        add_ipoint(Points, 0, -1, Points->x[0], Points->y[0], si);
+        add_ipoint(Points, np-2, -1, Points->x[np-1], Points->y[np-1], si);
+    }
+    G_debug(3, "    finding intersections...done");
+    
+    G_debug(3, "    postprocessing...");
+    if (si->ipallocated > si->ipcount) {
+        si->ipallocated = si->ipcount;
+        si->ip = G_realloc(si->ip, (si->ipcount)*sizeof(struct intersection_point));
+    }
+    for (i = 0; i < si->ilcount; i++) {
+        il = &(si->il[i]);
+        if (il->allocated > il->count) {
+            il->allocated = il->count;
+            il->a = G_realloc(il->a, (il->count)*sizeof(struct seg_intersection));
+        }
+        
+        if (il->count > 0) {
+            sort_intersection_list(il);
+            /* is it ok to use qsort here ? */
+        }
+    }
+    
+    /* si->ip will not be reallocated any more so we can use pointers */
+    sorted = G_malloc((si->ipcount)*sizeof(struct intersection_point *));
+    for (i = 0; i < si->ipcount; i++)
+        sorted[i] = &(si->ip[i]);
+    
+    qsort(sorted, si->ipcount, sizeof(struct intersection_point *), compare);
+    
+    /* assign groups */
+    group = 0; /* next available group number */
+    for (i = 0; i < si->ipcount; i++) {
+        
+        t = group;
+        for (j = i-1; j >= 0; j--) {
+            if (!FEQUAL(sorted[j]->x, sorted[i]->x, EPSILON))
+/*            if (!almost_equal(sorted[j]->x, sorted[i]->x, 16))*/
+                break;
+            if (FEQUAL(sorted[j]->y, sorted[i]->y, EPSILON)) {
+/*            if (almost_equal(sorted[j]->y, sorted[i]->y, 16)) {*/
+                t = sorted[j]->group;
+                break;
+            }
+        }
+        G_debug(4, "        group=%d, ip=%d", t, (int)(sorted[i] - &(si->ip[0])));
+        sorted[i]->group = t;
+        if (t == group)
+            group++;
+    }
+    si->group_count = group;
+    
+    G_debug(3, "    postprocessing...done");
+    
+    /* output contents of si */
+    for (i = 0; i < si->ilcount; i++) {
+        G_debug(4, "%d-%d :", i, i+1);
+        for (j = 0; j < si->il[i].count; j++) {
+            G_debug(4, "     %d-%d, group=%d", si->il[i].a[j].with, si->il[i].a[j].with+1, si->ip[si->il[i].a[j].ip].group);
+            G_debug(4, "            dist=%.18f", si->il[i].a[j].dist);
+            G_debug(4, "            x=%.18f, y=%.18f", si->ip[si->il[i].a[j].ip].x, si->ip[si->il[i].a[j].ip].y);
+        }
+    }
+    
+    return si;
+}
+
+/* create's graph with n vertices and allocates memory for e edges */
+/* trying to add more than e edges, produces fatal error */
+struct planar_graph* pg_create_struct(int n, int e) {
+    struct planar_graph *pg;
+    
+    pg = G_malloc(sizeof(struct planar_graph));
+    pg->vcount = n;
+    pg->v = G_malloc(n*sizeof(struct pg_vertex));
+    memset(pg->v, 0, n*sizeof(struct pg_vertex));
+    pg->ecount = 0;
+    pg->eallocated = MAX(e, 0);
+    pg->e = NULL;
+    pg->e = G_malloc(e*sizeof(struct pg_edge));
+    
+    return pg;
+}
+
+void pg_destroy_struct(struct planar_graph *pg) {
+    int i;
+    
+    for (i = 0; i < pg->vcount; i++) {
+        G_free(pg->v[i].edges);
+        G_free(pg->v[i].angles);
+    }
+    G_free(pg->v);
+    G_free(pg->e);
+    G_free(pg);
+}
+
+/* v1 and v2 must be valid */
+int pg_existsedge(struct planar_graph *pg, int v1, int v2) {
+    struct pg_vertex *v;
+    struct pg_edge *e;
+    int i, ecount;
+       
+    if (pg->v[v1].ecount <= pg->v[v2].ecount)
+        v = &(pg->v[v1]);
+    else
+        v = &(pg->v[v2]);
+        
+    ecount = v->ecount;
+    for (i = 0; i < ecount; i++) {
+        e = v->edges[i];
+        if (((e->v1 == v1) && (e->v2 == v2)) || ((e->v1 == v2) && (e->v2 == v1)))
+            return 1;
+    }
+    
+    return 0;
+}
+
+/* for internal use */
+void pg_addedge1(struct pg_vertex *v, struct pg_edge *e) {
+    if (v->ecount == v->eallocated) {
+        v->eallocated += 4;
+        v->edges = G_realloc(v->edges, (v->eallocated)*sizeof(struct pg_edge *));
+    }
+    v->edges[v->ecount] = e;
+    v->ecount++;
+}
+
+void pg_addedge(struct planar_graph *pg, int v1, int v2) {
+    struct pg_edge *e;
+    
+    G_debug(4, "pg_addedge(), v1=%d, v2=%d", v1, v2);
+    
+    if ((v1 == v2) || (v1 < 0) || (v1 >= pg->vcount) || (v2 < 0) || (v2 >= pg->vcount)) {
+        G_fatal_error("    pg_addedge(), v1 and/or v2 is invalid");
+        return;
+    }
+    
+    if (pg_existsedge(pg, v1, v2))
+        return;
+    
+    if (pg->ecount == pg->eallocated) {
+        G_fatal_error("Trying to add more edges to the planar_graph than the initial allocation size allows");
+    }
+    e = &(pg->e[pg->ecount]);
+    e->v1 = v1;
+    e->v2 = v2;
+    e->winding_left = 0; /* winding is undefined if the corresponding side is not visited */
+    e->winding_right = 0;
+    e->visited_left = 0;
+    e->visited_right = 0;
+    pg->ecount++;
+    pg_addedge1(&(pg->v[v1]), e);
+    pg_addedge1(&(pg->v[v2]), e);
+    
+    return;
+}
+
+struct planar_graph* pg_create(struct line_pnts *Points) {
+    struct seg_intersections *si;
+    struct planar_graph *pg;
+    struct intersection_point *ip;
+    struct pg_vertex *vert;
+    struct pg_edge *edge;
+    int i, j, t, v;
+
+    G_debug(3, "pg_create()");
+    
+    si = find_all_intersections(Points);
+    pg = pg_create_struct(si->group_count, 2*(si->ipcount));
+
+    /* set vertices info */
+    for (i = 0; i < si->ipcount; i++) {
+        ip = &(si->ip[i]);
+        t = ip->group;
+        pg->v[t].x = ip->x;
+        pg->v[t].y = ip->y;
+    }
+    
+    /* add all edges */
+    for (i = 0; i < si->ilcount; i++) {
+        v = si->ip[si->il[i].a[0].ip].group;
+        for (j = 1; j < si->il[i].count; j++) {
+            t = si->ip[si->il[i].a[j].ip].group;
+            if (t != v) {
+                pg_addedge(pg, v, t); /* edge direction is v ---> t */
+                v = t;
+            }
+        }
+    }
+    
+    /* precalculate angles with 0x */
+    for (i = 0; i < pg->vcount; i++) {
+        vert = &(pg->v[i]);
+        vert->angles = G_malloc((vert->ecount)*sizeof(double));
+        for (j = 0; j < vert->ecount; j++) {
+            edge = vert->edges[j];
+            t = (edge->v1 != i)?(edge->v1):(edge->v2);
+            vert->angles[j] = atan2(pg->v[t].y - vert->y, pg->v[t].x - vert->x);
+        }
+    }
+    
+    destroy_si_struct(si);
+    /*
+    I'm not sure if shrinking of the allocated memory always preserves it's physical place.
+    That's why I don't want to do this:
+    if (pg->ecount < pg->eallocated) {
+        pg->eallocated = pg->ecount;
+        pg->e = G_realloc(pg->e, (pg->ecount)*sizeof(struct pg_edge));
+    }
+    */
+    
+    /* very time consuming */
+    /*
+    for (i = 0; i < pg->vcount; i++) {
+        if (pg->v[i].ecount < pg->v[i].eallocated) {
+            pg->v[i].eallocated = pg->v[i].ecount;
+            pg->v[i].edges = G_realloc(pg->v[i].edges, (pg->v[i].ecount)*sizeof(struct pg_edges));
+        }
+    }
+    */
+    
+    /* output pg */
+    for (i = 0; i < pg->vcount; i++) {
+        G_debug(4, "    vertex %d (%g, %g)", i, pg->v[i].x, pg->v[i].y);
+        for (j = 0; j < pg->v[i].ecount; j++) {
+            G_debug(4, "        edge %d-%d", pg->v[i].edges[j]->v1, pg->v[i].edges[j]->v2);
+        }
+    }
+    
+    return pg;
+}

vector/v.parallel2/dgraph.h

@@ -0,0 +1,38 @@
+#ifndef DGRAPH_H
+#define DGRAPH_H
+
+/* pg comes from "planar graph" */
+/* every edge is directed. Nevertheless, we can visit it on both sides */
+struct pg_edge {
+    int v1; /* first vertex */
+    int v2; /* second vertex */
+    char visited_left;
+    char visited_right;
+    char winding_left; /* winding numbers */
+    char winding_right;
+};
+
+struct pg_vertex {
+    double x; /* coordinates */
+    double y;
+    int ecount; /* number of neighbours */
+    int eallocated; /* size of the array bellow */
+    struct pg_edge **edges; /* array of pointers */
+    double *angles; /* precalculated angles with Ox */
+};
+
+struct planar_graph {
+    int vcount; /* number of vertices */
+    struct pg_vertex *v;
+    int ecount;
+    int eallocated;
+    struct pg_edge *e;
+};
+
+struct planar_graph* pg_create_struct(int n, int e);
+void pg_destroy_struct(struct planar_graph *pg);
+int pg_existsedge(struct planar_graph *pg, int v1, int v2);
+void pg_addedge(struct planar_graph *pg, int v1, int v2);
+struct planar_graph* pg_create(struct line_pnts *Points);
+
+#endif

vector/v.parallel2/e_intersect.c

@@ -0,0 +1,918 @@
+#include <stdlib.h>
+#include <math.h>
+#include <grass/gis.h>
+#include "e_intersect.h"
+
+#define SWAP(a,b) {t = a; a = b; b = t;}
+#ifndef MIN
+    #define MIN(X,Y) ((X<Y)?X:Y)
+#endif
+#ifndef MAX
+    #define MAX(X,Y) ((X>Y)?X:Y)
+#endif    
+#define D (ax2-ax1)*(by1-by2) - (ay2-ay1)*(bx1-bx2)
+#define DA (bx1-ax1)*(by1-by2) - (by1-ay1)*(bx1-bx2)
+#define DB (ax2-ax1)*(by1-ay1) - (ay2-ay1)*(bx1-ax1)
+
+
+#ifdef ASDASDASFDSAFFDAS
+mpf_t p11, p12, p21, p22, t1, t2;
+mpf_t dd, dda, ddb, delta;
+mpf_t rra, rrb;
+
+int initialized = 0;
+
+void initialize_mpf_vars() {
+    mpf_set_default_prec(2048);
+    
+    mpf_init(p11);
+    mpf_init(p12);
+    mpf_init(p21);
+    mpf_init(p22);
+    
+    mpf_init(t1);
+    mpf_init(t2);
+    
+    mpf_init(dd);
+    mpf_init(dda);
+    mpf_init(ddb);
+    mpf_init(delta);
+    
+    mpf_init(rra);
+    mpf_init(rrb);
+    
+    initialized = 1;
+}
+
+/*
+  Caclulates:
+  |a11-b11  a12-b12|
+  |a21-b21  a22-b22|
+*/
+void det22(mpf_t rop, double a11, double b11, double a12, double b12, double a21, double b21, double a22, double b22) {
+    mpf_set_d(t1, a11);
+    mpf_set_d(t2, b11);
+    mpf_sub(p11, t1, t2);
+    mpf_set_d(t1, a12);
+    mpf_set_d(t2, b12);
+    mpf_sub(p12, t1, t2);
+    mpf_set_d(t1, a21);
+    mpf_set_d(t2, b21);
+    mpf_sub(p21, t1, t2);
+    mpf_set_d(t1, a22);
+    mpf_set_d(t2, b22);
+    mpf_sub(p22, t1, t2);
+    
+    mpf_mul(t1, p11, p22);
+    mpf_mul(t2, p12, p21);
+    mpf_sub(rop, t1, t2);
+    
+    return;
+}
+
+void swap(double *a, double *b) {
+    double t = *a;
+    *a = *b;
+    *b = t;
+    return;
+}
+
+/* multi-precision version */
+int segment_intersection_2d_e(double ax1, double ay1, double ax2, double ay2, double bx1, double by1, double bx2, double by2,
+    double *x1, double *y1, double *x2, double *y2)
+{
+    double t;
+    double max_ax, min_ax, max_ay, min_ay;
+    double max_bx, min_bx, max_by, min_by;
+    int sgn_d, sgn_da, sgn_db;
+    int vertical;
+    int f11, f12, f21, f22;
+    mp_exp_t exp;
+    char *s;
+    
+    if (!initialized)
+        initialize_mpf_vars();
+    
+    /* TODO: Works for points ? */
+    G_debug(3, "segment_intersection_2d_e()"); 
+    G_debug(4, "    ax1  = %.18f, ay1  = %.18f", ax1, ay1);
+    G_debug(4, "    ax2  = %.18f, ay2  = %.18f", ax2, ay2);
+    G_debug(4, "    bx1  = %.18f, by1  = %.18f", bx1, by1);
+    G_debug(4, "    bx2  = %.18f, by2  = %.18f", bx2, by2);
+
+    f11 = ((ax1 == bx1) && (ay1 == by1));
+    f12 = ((ax1 == bx2) && (ay1 == by2));
+    f21 = ((ax2 == bx1) && (ay2 == by1));
+    f22 = ((ax2 == bx2) && (ay2 == by2));
+    
+    /* Check for identical segments */
+    if ((f11 && f22) || (f12 && f21)) {
+        G_debug (3, "    identical segments" );
+        *x1 = ax1; *y1 = ay1;
+        *x2 = ax2; *y2 = ay2;
+        return 5;
+    }
+    /* Check for identical endpoints */
+    if (f11 || f12) {
+        G_debug (3, "    connected by endpoints" );
+        *x1 = ax1; *y1 = ay1;
+        return 1;
+    }
+    if (f21 || f22) {
+        G_debug (3, "    connected by endpoints" );
+        *x1 = ax2; *y1 = ay2;
+        return 1;
+    }
+
+    if ((MAX(ax1, ax2) < MIN(bx1, bx2)) || (MAX(bx1, bx2) < MIN(ax1, ax2))) {
+        G_debug(3, "    no intersection (disjoint bounding boxes)");
+        return 0;
+    }
+    if ((MAX(ay1, ay2) < MIN(by1, by2)) || (MAX(by1, by2) < MIN(ay1, ay2))) {
+        G_debug(3, "    no intersection (disjoint bounding boxes)");
+        return 0;
+    }
+        
+    det22(dd,  ax2, ax1, bx1, bx2, ay2, ay1, by1, by2);
+    sgn_d = mpf_sgn(dd);
+    if (sgn_d != 0) {
+        G_debug(3, "    general position");
+
+        det22(dda, bx1, ax1, bx1, bx2, by1, ay1, by1, by2);
+        sgn_da = mpf_sgn(dda);
+        
+        /*mpf_div(rra, dda, dd);
+        mpf_div(rrb, ddb, dd);
+        s = mpf_get_str(NULL, &exp, 10, 40, rra);
+        G_debug(4, "        ra = %sE%d", (s[0]==0)?"0":s, exp);
+        s = mpf_get_str(NULL, &exp, 10, 24, rrb);
+        G_debug(4, "        rb = %sE%d", (s[0]==0)?"0":s, exp);
+        */
+        
+        if (sgn_d > 0) {
+            if ((sgn_da < 0) || (mpf_cmp(dda, dd) > 0)) {
+                G_debug(3, "        no intersection");
+                return 0;
+            }
+            
+            det22(ddb, ax2, ax1, bx1, ax1, ay2, ay1, by1, ay1);
+            sgn_db = mpf_sgn(ddb);
+            if ((sgn_db < 0) || (mpf_cmp(ddb, dd) > 0)) {
+                G_debug(3, "        no intersection");
+                return 0;
+            }
+        }
+        else { /* if sgn_d < 0 */
+            if ((sgn_da > 0) || (mpf_cmp(dda, dd) < 0)) {
+                G_debug(3, "        no intersection");
+                return 0;
+            }
+            
+            det22(ddb, ax2, ax1, bx1, ax1, ay2, ay1, by1, ay1);
+            sgn_db = mpf_sgn(ddb);
+            if ((sgn_db > 0) || (mpf_cmp(ddb, dd) < 0)) {
+                G_debug(3, "        no intersection");
+                return 0;
+            }
+        }
+
+        /*G_debug(3, "        ra=%.17g rb=%.17g", mpf_get_d(dda)/mpf_get_d(dd), mpf_get_d(ddb)/mpf_get_d(dd));*/
+        /*G_debug(3, "        sgn_d=%d sgn_da=%d sgn_db=%d cmp(dda,dd)=%d cmp(ddb,dd)=%d", sgn_d, sgn_da, sgn_db, mpf_cmp(dda, dd), mpf_cmp(ddb, dd));*/
+    
+        mpf_set_d(delta, ax2 - ax1);
+        mpf_mul(t1, dda, delta);
+        mpf_div(t2, t1, dd);
+        *x1 = ax1 + mpf_get_d(t2);
+        
+        mpf_set_d(delta, ay2 - ay1);
+        mpf_mul(t1, dda, delta);
+        mpf_div(t2, t1, dd);
+        *y1 = ay1 + mpf_get_d(t2);
+
+        G_debug(3, "        intersection %.16g, %.16g", *x1, *y1);
+        return 1;
+    }
+    
+    /* segments are parallel or collinear */
+    det22(dda, bx1, ax1, bx1, bx2, by1, ay1, by1, by2);
+    sgn_da = mpf_sgn(dda);
+    if (sgn_da != 0) {
+        /* segments are parallel */
+        G_debug(3, "    parallel segments");
+        return 0;
+    }
+    
+    /* segments are colinear. check for overlap */
+    
+    /* swap endpoints if needed */
+    /* if segments are vertical, we swap x-coords with y-coords */  
+    vertical = 0;
+    if (ax1 > ax2) {
+        SWAP(ax1, ax2);
+        SWAP(ay1, ay2);
+    } else if (ax1 == ax2) {
+        vertical = 1;
+        if (ay1 > ay2)
+            SWAP(ay1, ay2);
+        SWAP(ax1, ay1);
+        SWAP(ax2, ay2);
+    }
+    if (bx1 > bx2) {
+        SWAP(bx1, bx2);
+        SWAP(by1, by2);
+    } else if (bx1 == bx2) {
+        if (by1 > by2)
+            SWAP(by1, by2);
+        SWAP(bx1, by1);
+        SWAP(bx2, by2);
+    }
+    
+    G_debug(3, "    collinear segments");
+
+    if ((bx2 < ax1) || (bx1 > ax2)) {
+        G_debug(3, "        no intersection");
+        return 0;
+    }
+
+    /* there is overlap or connected end points */
+    G_debug(3, "        overlap");
+    
+    /* a contains b */
+    if ((ax1 < bx1) && (ax2 > bx2)) {
+        G_debug(3, "            a contains b");
+        if (!vertical) {
+            *x1 = bx1; *y1 = by1;
+            *x2 = bx2; *y2 = by2;
+        }
+        else {
+            *x1 = by1; *y1 = bx1;
+            *x2 = by2; *y2 = bx2;
+        }
+  	    return 3;
+    }
+    
+    /* b contains a */
+    if ((ax1 > bx1) && (ax2 < bx2)) {
+        G_debug(3, "            b contains a");
+        if (!vertical) {
+            *x1 = bx1; *y1 = by1;
+            *x2 = bx2; *y2 = by2;
+        }
+        else {
+            *x1 = by1; *y1 = bx1;
+            *x2 = by2; *y2 = bx2;
+        }
+  	    return 4;
+    }   
+    
+    /* general overlap, 2 intersection points */
+    G_debug(3, "        partial overlap");
+    if ((bx1 > ax1) && (bx1 < ax2)) { /* b1 is in a */
+        if (!vertical) {
+            *x1 = bx1; *y1 = by1;
+            *x2 = ax2; *y2 = ay2;
+        }
+        else {
+            *x1 = by1; *y1 = bx1;
+            *x2 = ay2; *y2 = ax2;
+        }
+  	    return 2;
+    }
+    if ((bx2 > ax1) && (bx2 < ax2)) { /* b2 is in a */
+        if (!vertical) {
+            *x1 = bx2; *y1 = by2;
+            *x2 = ax1; *y2 = ay1;
+        }
+        else {
+            *x1 = by2; *y1 = bx2;
+            *x2 = ay1; *y2 = ax1;
+        }
+  	    return 2;
+    } 
+
+    /* should not be reached */
+    G_warning(("segment_intersection_2d() ERROR (should not be reached)"));
+    G_warning("%.16g %.16g", ax1, ay1);
+    G_warning("%.16g %.16g", ax2, ay2);
+    G_warning("x");
+    G_warning("%.16g %.16g", bx1, by1);
+    G_warning("%.16g %.16g", bx2, by2);
+
+    return 0;
+}
+#endif
+
+/* OLD */
+/* tollerance aware version */
+/* TODO: fix all ==s left */
+int segment_intersection_2d_tol(double ax1, double ay1, double ax2, double ay2, double bx1, double by1, double bx2, double by2,
+    double *x1, double *y1, double *x2, double *y2, double tol)
+{
+    double tola, tolb;
+    double d, d1, d2, ra, rb, t;
+    int    switched = 0;
+    
+    /* TODO: Works for points ? */
+    G_debug(4, "segment_intersection_2d()"); 
+    G_debug(4, "    ax1  = %.18f, ay1  = %.18f", ax1, ay1);
+    G_debug(4, "    ax2  = %.18f, ay2  = %.18f", ax2, ay2);
+    G_debug(4, "    bx1  = %.18f, by1  = %.18f", bx1, by1);
+    G_debug(4, "    bx2  = %.18f, by2  = %.18f", bx2, by2);
+
+    
+    /* Check identical lines */
+    if ((FEQUAL(ax1, bx1, tol) && FEQUAL(ay1, by1, tol) && FEQUAL(ax2, bx2, tol) && FEQUAL(ay2, by2, tol)) ||
+        (FEQUAL(ax1, bx2, tol) && FEQUAL(ay1, by2, tol) && FEQUAL(ax2, bx1, tol) && FEQUAL(ay2, by1, tol))) {
+        G_debug (2, " -> identical segments" ); 
+        *x1 = ax1; *y1 = ay1;
+        *x2 = ax2; *y2 = ay2;
+        return 5;
+    }
+    
+    /*  'Sort' lines by x1, x2, y1, y2 */
+    if ( bx1 < ax1 )
+        switched = 1;
+    else if ( bx1 == ax1 ) {
+        if ( bx2 < ax2 ) switched = 1;
+        else if ( bx2 == ax2 ) {
+            if ( by1 < ay1 ) switched = 1;
+            else if ( by1 == ay1 ) {
+                if ( by2 < ay2 ) switched = 1; /* by2 != ay2 (would be identical */
+            }
+        }
+    }
+    
+    if (switched) {
+        t = ax1; ax1 = bx1; bx1 = t; t = ay1; ay1 = by1; by1 = t; 
+        t = ax2; ax2 = bx2; bx2 = t; t = ay2; ay2 = by2; by2 = t;
+    }	
+    
+    d  = (ax2-ax1)*(by1-by2) - (ay2-ay1)*(bx1-bx2);
+    d1 = (bx1-ax1)*(by1-by2) - (by1-ay1)*(bx1-bx2);
+    d2 = (ax2-ax1)*(by1-ay1) - (ay2-ay1)*(bx1-ax1);
+    
+    G_debug(2, "    d  = %.18g", d);
+    G_debug(2, "    d1 = %.18g", d1);
+    G_debug(2, "    d2 = %.18g", d2);
+    
+    tola = tol/MAX(fabs(ax2-ax1), fabs(ay2-ay1));
+    tolb = tol/MAX(fabs(bx2-bx1), fabs(by2-by1));
+    G_debug(2, "    tol  = %.18g", tol);
+    G_debug(2, "    tola = %.18g", tola);
+    G_debug(2, "    tolb = %.18g", tolb);
+    if (!FZERO(d, tol)) {
+        ra = d1/d;
+        rb = d2/d;
+        
+        G_debug(2, "    not parallel/collinear: ra = %.18g", ra);
+        G_debug(2, "                            rb = %.18g", rb);
+        
+        if ((ra <= -tola) || (ra >= 1+tola) || (rb <= -tolb) || (rb >= 1+tolb)) {
+            G_debug(2, "        no intersection"); 
+            return 0;
+        }
+        
+        ra = MIN(MAX(ra, 0), 1);
+        *x1 = ax1 + ra*(ax2 - ax1);
+        *y1 = ay1 + ra*(ay2 - ay1);
+        
+        G_debug(2, "        intersection %.18f, %.18f", *x1, *y1); 
+        return 1;
+    }
+    
+    /* segments are parallel or collinear */
+    G_debug (3, " -> parallel/collinear" ); 
+    
+    if ((!FZERO(d1, tol)) || (!FZERO(d2, tol))) { /* lines are parallel */
+        G_debug (2, "  -> parallel" ); 
+        return 0;
+    }
+    
+    /* segments are colinear. check for overlap */
+    
+/*    aa = adx*adx + ady*ady;
+    bb = bdx*bdx + bdy*bdy;
+    
+    t = (ax1-bx1)*bdx + (ay1-by1)*bdy;*/
+    
+    
+    /* Collinear vertical */
+    /* original code assumed lines were not both vertical
+    *  so there is a special case if they are */
+    if (FEQUAL(ax1, ax2, tol) && FEQUAL(bx1, bx2, tol) && FEQUAL(ax1, bx1, tol)) {
+        G_debug(2, "  -> collinear vertical");
+        if (ay1 > ay2) { t=ay1; ay1=ay2; ay2=t;	} /* to be sure that ay1 < ay2 */
+        if (by1 > by2) { t=by1; by1=by2; by2=t; } /* to be sure that by1 < by2 */
+        if (ay1 > by2 || ay2 < by1) {
+            G_debug (2, "   -> no intersection");
+            return 0;
+        }
+
+        /* end points */
+        if (FEQUAL(ay1, by2, tol)) {
+            *x1 = ax1; *y1 = ay1;
+            G_debug(2, "   -> connected by end points");
+            return 1; /* endpoints only */
+        }
+        if (FEQUAL(ay2, by1, tol)) {
+            *x1 = ax2; *y1 = ay2;
+            G_debug (2, "  -> connected by end points");
+            return 1; /* endpoints only */
+        }
+        
+        /* general overlap */
+        G_debug(3, "   -> vertical overlap");
+        /* a contains b */
+        if (ay1 <= by1 && ay2 >= by2) {
+            G_debug (2, "    -> a contains b" ); 
+           *x1 = bx1; *y1 = by1;
+            *x2 = bx2; *y2 = by2;
+            if (!switched)
+                return 3; 
+            else
+                return 4;
+        }
+        /* b contains a */
+        if ( ay1 >= by1 && ay2 <= by2 ) {
+            G_debug (2, "    -> b contains a" );
+            *x1 = ax1; *y1 = ay1;
+            *x2 = ax2; *y2 = ay2;
+            if ( !switched )
+                return 4; 
+            else
+                return 3;
+        }
+
+        /* general overlap, 2 intersection points */
+        G_debug (2, "    -> partial overlap" ); 
+        if ( by1 > ay1 && by1 < ay2 ) { /* b1 in a */
+            if ( !switched ) {
+                *x1 = bx1; *y1 = by1;
+                *x2 = ax2; *y2 = ay2;
+            } else {
+                *x1 = ax2; *y1 = ay2;
+                *x2 = bx1; *y2 = by1;
+            }
+            return 2;
+        }
+        
+        if ( by2 > ay1 && by2 < ay2 ) { /* b2 in a */
+            if ( !switched ) {
+                *x1 = bx2; *y1 = by2;
+                *x2 = ax1; *y2 = ay1;
+            } else {
+                *x1 = ax1; *y1 = ay1;
+                *x2 = bx2; *y2 = by2;
+            }
+            return 2;
+        } 
+	
+        /* should not be reached */
+        G_warning(("Vect_segment_intersection() ERROR (collinear vertical segments)"));
+        G_warning("%.15g %.15g", ax1, ay1);
+        G_warning("%.15g %.15g", ax2, ay2);
+        G_warning("x");
+        G_warning("%.15g %.15g", bx1, by1);
+        G_warning("%.15g %.15g", bx2, by2);
+        return 0;
+    }
+    
+    G_debug (2, "   -> collinear non vertical" ); 
+    
+    /* Collinear non vertical */
+    if ( ( bx1 > ax1 && bx2 > ax1 && bx1 > ax2 && bx2 > ax2 ) || 
+         ( bx1 < ax1 && bx2 < ax1 && bx1 < ax2 && bx2 < ax2 ) ) {
+        G_debug (2, "   -> no intersection" ); 
+	return 0;
+    }
+
+    /* there is overlap or connected end points */
+    G_debug (2, "   -> overlap/connected end points" ); 
+
+    /* end points */
+    if ( (ax1 == bx1 && ay1 == by1) || (ax1 == bx2 && ay1 == by2) ) {
+	*x1 = ax1; *y1 = ay1;
+        G_debug (2, "    -> connected by end points");
+	return 1; 
+    }
+    if ( (ax2 == bx1 && ay2 == by1) || (ax2 == bx2 && ay2 == by2) ) {
+	*x1 = ax2; *y1 = ay2;
+        G_debug (2, "    -> connected by end points");
+	return 1;
+    }
+    
+    if (ax1 > ax2) { t=ax1; ax1=ax2; ax2=t; t=ay1; ay1=ay2; ay2=t; } /* to be sure that ax1 < ax2 */
+    if (bx1 > bx2) { t=bx1; bx1=bx2; bx2=t; t=by1; by1=by2; by2=t; } /* to be sure that bx1 < bx2 */
+    
+    /* a contains b */
+    if ( ax1 <= bx1 && ax2 >= bx2 ) {
+    	G_debug (2, "    -> a contains b" ); 
+        *x1 = bx1; *y1 = by1;
+    	*x2 = bx2; *y2 = by2;
+        if ( !switched )
+       	    return 3; 
+        else 
+            return 4;
+    }
+    /* b contains a */
+    if ( ax1 >= bx1 && ax2 <= bx2 ) {
+        G_debug (2, "    -> b contains a" ); 
+        *x1 = ax1; *y1 = ay1;
+        *x2 = ax2; *y2 = ay2;
+        if ( !switched )
+            return 4;
+        else
+            return 3;
+    }   
+    
+    /* general overlap, 2 intersection points (lines are not vertical) */
+    G_debug (2, "    -> partial overlap" ); 
+    if ( bx1 > ax1 && bx1 < ax2 ) { /* b1 is in a */
+        if ( !switched ) {
+	    *x1 = bx1; *y1 = by1;
+	    *x2 = ax2; *y2 = ay2;
+	} else {
+	    *x1 = ax2; *y1 = ay2;
+	    *x2 = bx1; *y2 = by1;
+        }
+	return 2;
+    } 
+    if ( bx2 > ax1 && bx2 < ax2 ) { /* b2 is in a */
+        if ( !switched ) {
+	    *x1 = bx2; *y1 = by2;
+	    *x2 = ax1; *y2 = ay1;
+	} else {
+	    *x1 = ax1; *y1 = ay1;
+	    *x2 = bx2; *y2 = by2;
+        }
+	return 2;
+    } 
+
+    /* should not be reached */
+    G_warning(("segment_intersection_2d() ERROR (collinear non vertical segments)"));
+    G_warning("%.15g %.15g", ax1, ay1);
+    G_warning("%.15g %.15g", ax2, ay2);
+    G_warning("x");
+    G_warning("%.15g %.15g", bx1, by1);
+    G_warning("%.15g %.15g", bx2, by2);
+
+    return 0;
+}
+
+int segment_intersection_2d(double ax1, double ay1, double ax2, double ay2, double bx1, double by1, double bx2, double by2,
+    double *x1, double *y1, double *x2, double *y2)
+{
+    const int DLEVEL = 4;
+    double t;
+    int vertical;
+    int f11, f12, f21, f22;
+    double d, da, db;
+    
+    /* TODO: Works for points ? */
+    G_debug(DLEVEL, "segment_intersection_2d()"); 
+    G_debug(4, "    ax1  = %.18f, ay1  = %.18f", ax1, ay1);
+    G_debug(4, "    ax2  = %.18f, ay2  = %.18f", ax2, ay2);
+    G_debug(4, "    bx1  = %.18f, by1  = %.18f", bx1, by1);
+    G_debug(4, "    bx2  = %.18f, by2  = %.18f", bx2, by2);
+
+    f11 = ((ax1 == bx1) && (ay1 == by1));
+    f12 = ((ax1 == bx2) && (ay1 == by2));
+    f21 = ((ax2 == bx1) && (ay2 == by1));
+    f22 = ((ax2 == bx2) && (ay2 == by2));
+    
+    /* Check for identical segments */
+    if ((f11 && f22) || (f12 && f21)) {
+        G_debug(DLEVEL, "    identical segments" );
+        *x1 = ax1; *y1 = ay1;
+        *x2 = ax2; *y2 = ay2;
+        return 5;
+    }
+    /* Check for identical endpoints */
+    if (f11 || f12) {
+        G_debug(DLEVEL, "    connected by endpoints" );
+        *x1 = ax1; *y1 = ay1;
+        return 1;
+    }
+    if (f21 || f22) {
+        G_debug (DLEVEL, "    connected by endpoints" );
+        *x1 = ax2; *y1 = ay2;
+        return 1;
+    }
+
+    if ((MAX(ax1, ax2) < MIN(bx1, bx2)) || (MAX(bx1, bx2) < MIN(ax1, ax2))) {
+        G_debug(DLEVEL, "    no intersection (disjoint bounding boxes)");
+        return 0;
+    }
+    if ((MAX(ay1, ay2) < MIN(by1, by2)) || (MAX(by1, by2) < MIN(ay1, ay2))) {
+        G_debug(DLEVEL, "    no intersection (disjoint bounding boxes)");
+        return 0;
+    }
+        
+    d  = D;
+    if (d != 0) {
+        G_debug(DLEVEL, "    general position");
+
+        da = DA;
+        
+        /*mpf_div(rra, dda, dd);
+        mpf_div(rrb, ddb, dd);
+        s = mpf_get_str(NULL, &exp, 10, 40, rra);
+        G_debug(4, "        ra = %sE%d", (s[0]==0)?"0":s, exp);
+        s = mpf_get_str(NULL, &exp, 10, 24, rrb);
+        G_debug(4, "        rb = %sE%d", (s[0]==0)?"0":s, exp);
+        */
+        
+        if (d > 0) {
+            if ((da < 0) || (da > d)) {
+                G_debug(DLEVEL, "        no intersection");
+                return 0;
+            }
+            
+            db = DB;
+            if ((db < 0) || (db > d)) {
+                G_debug(DLEVEL, "        no intersection");
+                return 0;
+            }
+        }
+        else { /* if d < 0 */
+            if ((da > 0) || (da < d)) {
+                G_debug(DLEVEL, "        no intersection");
+                return 0;
+            }
+            
+            db = DB;
+            if ((db > 0) || (db < d)) {
+                G_debug(DLEVEL, "        no intersection");
+                return 0;
+            }
+        }
+
+        /*G_debug(DLEVEL, "        ra=%.17g rb=%.17g", mpf_get_d(dda)/mpf_get_d(dd), mpf_get_d(ddb)/mpf_get_d(dd));*/
+        /*G_debug(DLEVEL, "        sgn_d=%d sgn_da=%d sgn_db=%d cmp(dda,dd)=%d cmp(ddb,dd)=%d", sgn_d, sgn_da, sgn_db, mpf_cmp(dda, dd), mpf_cmp(ddb, dd));*/
+    
+        *x1 = ax1 + (ax2 - ax1)*da/d;
+        *y1 = ay1 + (ay2 - ay1)*da/d;
+        
+        G_debug(DLEVEL, "        intersection %.16g, %.16g", *x1, *y1);
+        return 1;
+    }
+    
+    /* segments are parallel or collinear */
+    da = DA;
+    db = DB;
+    if ((da != 0) || (db != 0)) {
+        /* segments are parallel */
+        G_debug(DLEVEL, "    parallel segments");
+        return 0;
+    }
+    
+    /* segments are colinear. check for overlap */
+    
+    /* swap endpoints if needed */
+    /* if segments are vertical, we swap x-coords with y-coords */  
+    vertical = 0;
+    if (ax1 > ax2) {
+        SWAP(ax1, ax2);
+        SWAP(ay1, ay2);
+    } else if (ax1 == ax2) {
+        vertical = 1;
+        if (ay1 > ay2)
+            SWAP(ay1, ay2);
+        SWAP(ax1, ay1);
+        SWAP(ax2, ay2);
+    }
+    if (bx1 > bx2) {
+        SWAP(bx1, bx2);
+        SWAP(by1, by2);
+    } else if (bx1 == bx2) {
+        if (by1 > by2)
+            SWAP(by1, by2);
+        SWAP(bx1, by1);
+        SWAP(bx2, by2);
+    }
+    
+    G_debug(DLEVEL, "    collinear segments");
+
+    if ((bx2 < ax1) || (bx1 > ax2)) {
+        G_debug(DLEVEL, "        no intersection");
+        return 0;
+    }
+
+    /* there is overlap or connected end points */
+    G_debug(DLEVEL, "        overlap");
+    
+    /* a contains b */
+    if ((ax1 < bx1) && (ax2 > bx2)) {
+        G_debug(DLEVEL, "            a contains b");
+        if (!vertical) {
+            *x1 = bx1; *y1 = by1;
+            *x2 = bx2; *y2 = by2;
+        }
+        else {
+            *x1 = by1; *y1 = bx1;
+            *x2 = by2; *y2 = bx2;
+        }
+  	    return 3;
+    }
+    
+    /* b contains a */
+    if ((ax1 > bx1) && (ax2 < bx2)) {
+        G_debug(DLEVEL, "            b contains a");
+        if (!vertical) {
+            *x1 = bx1; *y1 = by1;
+            *x2 = bx2; *y2 = by2;
+        }
+        else {
+            *x1 = by1; *y1 = bx1;
+            *x2 = by2; *y2 = bx2;
+        }
+  	    return 4;
+    }   
+    
+    /* general overlap, 2 intersection points */
+    G_debug(DLEVEL, "        partial overlap");
+    if ((bx1 > ax1) && (bx1 < ax2)) { /* b1 is in a */
+        if (!vertical) {
+            *x1 = bx1; *y1 = by1;
+            *x2 = ax2; *y2 = ay2;
+        }
+        else {
+            *x1 = by1; *y1 = bx1;
+            *x2 = ay2; *y2 = ax2;
+        }
+  	    return 2;
+    }
+    if ((bx2 > ax1) && (bx2 < ax2)) { /* b2 is in a */
+        if (!vertical) {
+            *x1 = bx2; *y1 = by2;
+            *x2 = ax1; *y2 = ay1;
+        }
+        else {
+            *x1 = by2; *y1 = bx2;
+            *x2 = ay1; *y2 = ax1;
+        }
+  	    return 2;
+    } 
+
+    /* should not be reached */
+    G_warning(("segment_intersection_2d() ERROR (should not be reached)"));
+    G_warning("%.16g %.16g", ax1, ay1);
+    G_warning("%.16g %.16g", ax2, ay2);
+    G_warning("x");
+    G_warning("%.16g %.16g", bx1, by1);
+    G_warning("%.16g %.16g", bx2, by2);
+
+    return 0;
+}
+
+#define N 52 /* double's mantisa size in bits */
+/* a and b are different in at most <bits> significant digits */
+int almost_equal(double a, double b, int bits) {
+    int ea, eb, e;
+    
+    if (a == b)
+        return 1;
+
+    if (a == 0 || b == 0) {
+        /* return (0 < -N+bits); */
+        return (bits > N);
+    }
+    
+    frexp(a, &ea);
+    frexp(b, &eb);
+    if (ea != eb)
+        return (bits > N + abs(ea-eb));
+    frexp(a-b, &e);
+    return (e < ea-N+bits);
+}
+
+#ifdef ASDASDFASFEAS
+int segment_intersection_2d_test(double ax1, double ay1, double ax2, double ay2, double bx1, double by1, double bx2, double by2, double *x1, double *y1, double *x2, double *y2) {
+    double t;
+    double max_ax, min_ax, max_ay, min_ay;
+    double max_bx, min_bx, max_by, min_by;
+    int sgn_d, sgn_da, sgn_db;
+    int vertical;
+    int f11, f12, f21, f22;
+    mp_exp_t exp;
+    char *s;
+    double d, da, db, ra, rb;
+    
+    if (!initialized)
+        initialize_mpf_vars();
+    
+    /* TODO: Works for points ? */
+    G_debug(0, "segment_intersection_2d_test()"); 
+    G_debug(0, "    ax1  = %.18e, ay1  = %.18e", ax1, ay1);
+    G_debug(0, "    ax2  = %.18e, ay2  = %.18e", ax2, ay2);
+    G_debug(0, "    bx1  = %.18e, by1  = %.18e", bx1, by1);
+    G_debug(0, "    bx2  = %.18e, by2  = %.18e", bx2, by2);
+
+    f11 = ((ax1 == bx1) && (ay1 == by1));
+    f12 = ((ax1 == bx2) && (ay1 == by2));
+    f21 = ((ax2 == bx1) && (ay2 == by1));
+    f22 = ((ax2 == bx2) && (ay2 == by2));
+    
+    /* Check for identical segments */
+    if ((f11 && f22) || (f12 && f21)) {
+        G_debug (0, "    identical segments" );
+        *x1 = ax1; *y1 = ay1;
+        *x2 = ax2; *y2 = ay2;
+        return 5;
+    }
+    /* Check for identical endpoints */
+    if (f11 || f12) {
+        G_debug (0, "    connected by endpoints" );
+        *x1 = ax1; *y1 = ay1;
+        return 1;
+    }
+    if (f21 || f22) {
+        G_debug (0, "    connected by endpoints" );
+        *x1 = ax2; *y1 = ay2;
+        return 1;
+    }
+
+    if ((MAX(ax1, ax2) < MIN(bx1, bx2)) || (MAX(bx1, bx2) < MIN(ax1, ax2))) {
+        G_debug(0, "    no intersection (disjoint bounding boxes)");
+        return 0;
+    }
+    if ((MAX(ay1, ay2) < MIN(by1, by2)) || (MAX(by1, by2) < MIN(ay1, ay2))) {
+        G_debug(0, "    no intersection (disjoint bounding boxes)");
+        return 0;
+    }
+    
+    d  = (ax2-ax1)*(by1-by2) - (ay2-ay1)*(bx1-bx2);
+    da = (bx1-ax1)*(by1-by2) - (by1-ay1)*(bx1-bx2);
+    db = (ax2-ax1)*(by1-ay1) - (ay2-ay1)*(bx1-ax1);
+    
+    det22(dd,  ax2, ax1, bx1, bx2, ay2, ay1, by1, by2);
+    sgn_d = mpf_sgn(dd);
+    s = mpf_get_str(NULL, &exp, 10, 40, dd);
+    G_debug(0, "    dd = %sE%d", (s[0]==0)?"0":s, exp);
+    G_debug(0, "    d = %.18E", d);
+    
+    if (sgn_d != 0) {
+        G_debug(0, "    general position");
+
+        det22(dda, bx1, ax1, bx1, bx2, by1, ay1, by1, by2);
+        det22(ddb, ax2, ax1, bx1, ax1, ay2, ay1, by1, ay1);
+        sgn_da = mpf_sgn(dda);
+        sgn_db = mpf_sgn(ddb);
+        
+        ra = da/d;
+        rb = db/d;
+        mpf_div(rra, dda, dd);
+        mpf_div(rrb, ddb, dd);
+
+        s = mpf_get_str(NULL, &exp, 10, 40, rra);
+        G_debug(0, "        rra = %sE%d", (s[0]==0)?"0":s, exp);
+        G_debug(0, "        ra = %.18E", ra);
+        s = mpf_get_str(NULL, &exp, 10, 40, rrb);
+        G_debug(0, "        rrb = %sE%d", (s[0]==0)?"0":s, exp);
+        G_debug(0, "        rb = %.18E", rb);
+        
+        if (sgn_d > 0) {
+            if ((sgn_da < 0) || (mpf_cmp(dda, dd) > 0)) {
+                G_debug(DLEVEL, "        no intersection");
+                return 0;
+            }
+            
+            if ((sgn_db < 0) || (mpf_cmp(ddb, dd) > 0)) {
+                G_debug(DLEVEL, "        no intersection");
+                return 0;
+            }
+        }
+        else { /* if sgn_d < 0 */
+            if ((sgn_da > 0) || (mpf_cmp(dda, dd) < 0)) {
+                G_debug(DLEVEL, "        no intersection");
+                return 0;
+            }
+            
+            if ((sgn_db > 0) || (mpf_cmp(ddb, dd) < 0)) {
+                G_debug(DLEVEL, "        no intersection");
+                return 0;
+            }
+        }
+
+        mpf_set_d(delta, ax2 - ax1);
+        mpf_mul(t1, dda, delta);
+        mpf_div(t2, t1, dd);
+        *x1 = ax1 + mpf_get_d(t2);
+        
+        mpf_set_d(delta, ay2 - ay1);
+        mpf_mul(t1, dda, delta);
+        mpf_div(t2, t1, dd);
+        *y1 = ay1 + mpf_get_d(t2);
+
+        G_debug(0, "        intersection at:");
+        G_debug(0, "            xx = %.18e", *x1);
+        G_debug(0, "             x = %.18e", ax1 + ra*(ax2-ax1));
+        G_debug(0, "            yy = %.18e", *y1);
+        G_debug(0, "             y = %.18e", ay1 + ra*(ay2-ay1));
+        return 1;
+    }
+    
+    G_debug(0, "    parallel/collinear...");
+    return -1;
+}
+#endif

vector/v.parallel2/e_intersect.h

@@ -0,0 +1,21 @@
+#ifndef E_INTERSECT_H
+#define E_INTERSECT_H
+
+#define FZERO(X, TOL) (fabs(X)<TOL)
+#define FEQUAL(X, Y, TOL) (fabs(X-Y)<TOL)
+
+/*int segment_intersection_2d_e(double ax1, double ay1, double ax2, double ay2, double bx1, double by1, double bx2, double by2,
+    double *x1, double *y1, double *x2, double *y2);
+int segment_intersection_2d_test(double ax1, double ay1, double ax2, double ay2, double bx1, double by1, double bx2, double by2,
+    double *x1, double *y1, double *x2, double *y2);*/
+
+int segment_intersection_2d_tol(double ax1, double ay1, double ax2, double ay2, double bx1, double by1, double bx2, double by2,
+    double *x1, double *y1, double *x2, double *y2, double tol);
+
+int segment_intersection_2d(double ax1, double ay1, double ax2, double ay2, double bx1, double by1, double bx2, double by2,
+    double *x1, double *y1, double *x2, double *y2);
+
+    
+int almost_equal(double a, double b, int bits);
+
+#endif

vector/v.parallel2/local_proto.h

@@ -0,0 +1,9 @@
+#ifndef LOCAL_PROTO_H
+#define LOCAL_PROTO_H
+
+void Vect_line_buffer2(struct line_pnts *Points, double da, double db, double dalpha, int round, int caps, double tol, struct line_pnts **oPoints, struct line_pnts ***iPoints, int *inner_count);
+void Vect_area_buffer2(struct Map_info *Map, int area, double da, double db, double dalpha, int round, int caps, double tol, struct line_pnts **oPoints, struct line_pnts ***iPoints, int *inner_count);
+void Vect_point_buffer2(double px, double py, double da, double db, double dalpha, int round, double tol, struct line_pnts **oPoints);
+void Vect_line_parallel2(struct line_pnts *InPoints, double da, double db, double dalpha, int side, int round, double tol, struct line_pnts *OutPoints);
+
+#endif

vector/v.parallel2/main.c

@@ -0,0 +1,183 @@
+/***************************************************************
+ *
+ * MODULE:       v.parallel
+ * 
+ * AUTHOR(S):    Radim Blazek, Rosen Matev
+ *               
+ * PURPOSE:      Create parallel lines
+ *               
+ * COPYRIGHT:    (C) 2008 by the GRASS Development Team
+ *
+ *               This program is free software under the 
+ *               GNU General Public License (>=v2). 
+ *               Read the file COPYING that comes with GRASS
+ *               for details.
+ *
+ **************************************************************/
+#include <stdlib.h> 
+#include <math.h>
+#include <grass/gis.h>
+#include <grass/Vect.h>
+#include <grass/glocale.h>
+#include "local_proto.h"
+
+int main (int argc, char *argv[])
+{
+    struct GModule *module;
+    struct Option *in_opt, *out_opt, *dista_opt;
+    struct Option *distb_opt, *angle_opt, *side_opt;
+    struct Option *tol_opt;
+    struct Flag *round_flag, *buf_flag;
+    struct Map_info In, Out;
+    struct line_pnts *Points, *Points2, *oPoints, **iPoints;
+    struct line_cats *Cats;
+    int    line, nlines, inner_count, j;
+    double da, db, dalpha, tolerance;
+    int side;
+
+    G_gisinit(argv[0]);
+
+    module = G_define_module();
+    module->keywords = _("vector, geometry");
+    module->description = _("Create parallel line to input lines");
+
+    in_opt = G_define_standard_option(G_OPT_V_INPUT);
+    out_opt = G_define_standard_option(G_OPT_V_OUTPUT);
+    /* layer_opt = G_define_standard_option(G_OPT_V_FIELD); */
+    
+    dista_opt = G_define_option();
+    dista_opt->key = "distance";
+    dista_opt->type =  TYPE_DOUBLE;
+    dista_opt->required = YES;
+    dista_opt->options = "0-100000000";
+    dista_opt->multiple = NO;
+    dista_opt->description = _("Offset along major axis in map units");
+
+    distb_opt = G_define_option();
+    distb_opt->key = "minordistance";
+    distb_opt->type =  TYPE_DOUBLE;
+    distb_opt->required = NO;
+    distb_opt->options = "0-100000000";
+    distb_opt->multiple = NO;
+    distb_opt->description = _("Offset along minor axis in map units");
+
+    angle_opt = G_define_option();
+    angle_opt->key = "angle";
+    angle_opt->type =  TYPE_DOUBLE;
+    angle_opt->required = NO;
+    angle_opt->answer = "0";
+    angle_opt->multiple = NO;
+    angle_opt->description = _("Angle of major axis in degrees");
+
+    side_opt = G_define_option();
+    side_opt->key = "side";
+    side_opt->type =  TYPE_STRING;
+    side_opt->required = YES;
+    side_opt->answer = "right";
+    side_opt->multiple = NO;
+    side_opt->options = "left,right,both";
+    side_opt->description = _("left;Parallel line is on the left;right;Parallel line is on the right;both;Parallel lines on both sides");
+
+    tol_opt = G_define_option();
+    tol_opt->key = "tolerance";
+    tol_opt->type =  TYPE_DOUBLE;
+    tol_opt->required = NO;
+    tol_opt->options = "0-100000000";
+    tol_opt->multiple = NO;
+    tol_opt->description = _("Tolerance of arc polylines in map units");
+
+    round_flag = G_define_flag();
+    round_flag->key = 'r';
+    round_flag->description = _("Make outside corners round");
+
+    buf_flag = G_define_flag();
+    buf_flag->key = 'b';
+    buf_flag->description = _("Create buffer-like parallel lines");
+    
+    if (G_parser (argc, argv))
+        exit(EXIT_FAILURE);
+
+    /* layer = atoi ( layer_opt->answer ); */
+    da = atof(dista_opt->answer);
+    
+    if (distb_opt->answer)
+        db = atof(distb_opt->answer);
+    else
+        db = da;
+        
+    if (angle_opt->answer)
+        dalpha = atof(angle_opt->answer);
+    else
+        dalpha = 0;
+        
+    if (tol_opt->answer)
+        tolerance = atof(tol_opt->answer);
+    else
+        tolerance = ((db<da)?db:da)/100.;
+            
+    if (strcmp(side_opt->answer, "right") == 0)
+        side = 1;
+    else if (strcmp(side_opt->answer, "left") == 0)
+        side = -1;
+    else
+        side = 0;
+
+    Vect_set_open_level(2); 
+    Vect_open_old (&In, in_opt->answer, ""); 
+    Vect_open_new (&Out, out_opt->answer, 0);
+    Vect_copy_head_data (&In, &Out);
+    Vect_hist_copy (&In, &Out);
+    Vect_hist_command ( &Out );
+    
+    Points = Vect_new_line_struct ();
+    Points2 = Vect_new_line_struct ();
+    Cats = Vect_new_cats_struct ();
+
+    nlines = Vect_get_num_lines ( &In );
+
+    for ( line = 1; line <= nlines; line++ ) {
+        int ltype;
+        
+        G_percent(line, nlines, 1);
+        
+        ltype = Vect_read_line ( &In, Points, Cats, line);
+        
+        if ( ltype & GV_LINES ) {
+            if (!(buf_flag->answer)) {
+                if (side != 0) {
+                    Vect_line_parallel2(Points, da, db, dalpha, side, round_flag->answer, tolerance, Points2);
+                    Vect_write_line(&Out, ltype, Points2, Cats);
+                }
+                else {
+                    Vect_line_parallel2(Points, da, db, dalpha, 1, round_flag->answer, tolerance, Points2);
+                    Vect_write_line(&Out, ltype, Points2, Cats);
+                    Vect_line_parallel2(Points, da, db, dalpha, -1, round_flag->answer, tolerance, Points2);
+                    Vect_write_line(&Out, ltype, Points2, Cats);
+                }   
+            }
+            else {
+                Vect_line_buffer2(Points, da, db, dalpha, round_flag->answer, 1, tolerance, &oPoints, &iPoints, &inner_count);
+                Vect_write_line(&Out, ltype, oPoints, Cats);
+                for (j = 0; j < inner_count; j++) {
+                    Vect_write_line(&Out, ltype, iPoints[j], Cats); 
+                }
+            }
+        } else {
+            Vect_write_line(&Out, ltype, Points, Cats);
+        }
+    }
+    
+/*    Vect_build_partial(&Out, GV_BUILD_BASE);
+    Vect_snap_lines(&Out, GV_BOUNDARY, 1e-7, NULL);
+    Vect_break_lines(&Out, GV_BOUNDARY, NULL);
+    Vect_remove_duplicates(&Out, GV_BOUNDARY, NULL);
+    Vect_build_partial (&Out, GV_BUILD_NONE);
+ */
+    Vect_build (&Out);
+    
+    Vect_close (&In);
+    Vect_close (&Out);
+
+    exit(EXIT_SUCCESS) ;
+}
+

vector/v.parallel2/v.parallel.html

@@ -0,0 +1,17 @@
+<H2>DESCRIPTION</H2>
+
+<EM>v.parallel</EM> create parallel line to input vector lines which
+can be used as half-buffers.
+
+<H2>SEE ALSO</H2>
+
+<EM>
+<A HREF="v.buffer.html">v.buffer</A>
+</EM>
+
+<H2>AUTHORS</H2>
+
+Radim Blazek<br>
+Rewritten by Rosen Matev (with support through the Google Summer of Code program 2008)
+
+<p><i>Last changed: $Date: 2005-11-15 07:46:14 +0100 (Tue, 15 Nov 2005) $</i>