Moved the unsuccessful indexing code out of testbed and renamed it

feature-120-cell-index
Mike Lynch 2023-08-19 16:23:29 +10:00
parent 34c9755bd1
commit aa5501e14a
3 changed files with 339 additions and 0 deletions

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// bad stuff
function find_chords(chords, n) {
return chords.filter((c) => c[0].id === n.id || c[1].id === n.id);
}
function find_neighbours(chords, n) {
const c = find_chords(chords, n);
return c.map((c) => c[0].id === n.id ? c[1] : c[0])
}
// for a list of pairs [n1, n2] (these are nodes which share a common angle
// from a center), find all the groups of nodes which don't appear in a pair
// together
function partition_nodes(pairs) {
let groups = [];
const seen = new Set();
for( const pair of pairs ) {
// both nodes are in a group already
if( seen.has(pair[0]) && seen.has(pair[1]) ) {
continue;
}
let already = false;
// check if either node is already in a group
for( const group of groups ) {
if( group.has(pair[0]) ) {
group.add(pair[1]);
seen.add(pair[1]);
already = true;
continue;
} else if( group.has(pair[1]) ) {
group.has(pair[0]);
seen.has(pair[0]);
already = true;
continue;
}
}
// if neither of the pair was in a former group, start a new group
if( !already ) {
groups.push(new Set(pair));
}
// collapse any groups which now have common elements
groups = collapse_groups(groups);
}
return groups;
}
// given a list of groups, if any have common elements, collapse them
function collapse_groups(groups) {
const new_groups = [ ];
for( group of groups ) {
let collapsed = false;
for( new_group of new_groups ) {
const i = intersection(group, new_group);
if( i.size > 0 ) {
for( const e of group ) {
new_group.add(e);
}
collapsed = true;
break;
}
}
if( !collapsed ) {
new_groups.push(new Set(group));
}
}
return new_groups;
}
function intersection(s1, s2) {
const i = new Set();
for( const e of s1 ) {
if( s2.has(e) ) {
i.add(e)
}
}
return i;
}
function union(s1, s2) {
const u = new Set(s1);
for( const e of s2 ) {
u.add(e);
}
return u;
}
function vector_angle(n1, n2, n3) {
const v1 = new THREE.Vector4(n1.x, n1.y, n1.z, n1.w);
const v2 = new THREE.Vector4(n2.x, n2.y, n2.z, n2.w);
const v3 = new THREE.Vector4(n3.x, n3.y, n3.z, n3.w);
v2.sub(v1);
v3.sub(v1);
const dp = v2.dot(v3);
return Math.acos(dp / ( v2.length() * v3.length()));
}
function neighbour_angles_orig(chords, n) {
const ns = find_neighbours(chords, n);
const angles = {};
for( let i = 0; i < ns.length - 1; i++ ) {
for( let j = i + 1; j < ns.length; j++ ) {
const n2 = ns[i];
const n3 = ns[j];
const a = THREE.MathUtils.radToDeg(vector_angle(n, n2, n3));
const af = (a).toFixed(3);
if( ! (af in angles) ) {
angles[af] = [];
}
angles[af].push([n2.id, n3.id]);
}
}
return angles;
}
function neighbour_angles(chords, n, angle) {
const ns = find_neighbours(chords, n);
const pairs = [];
for( let i = 0; i < ns.length - 1; i++ ) {
for( let j = i + 1; j < ns.length; j++ ) {
const n2 = ns[i];
const n3 = ns[j];
const a = THREE.MathUtils.radToDeg(vector_angle(n, n2, n3));
const af = (a).toFixed(3);
if( af === angle ) {
pairs.push([n2.id, n3.id]);
}
}
}
return pairs;
}
function make_120_partition(nodes, n) {
const chords = find_all_chords(nodes);
const chord3 = chords["1.74806"]; // these are edges of the 600-cells;
const pairs60 = neighbour_angles(chord3, n, "60.000");
const icosas = partition_nodes(pairs60);
n.label = 1;
const angles = icosa_nodes(nodes, icosas[0]);
label_120_partition_r(nodes, chord3, 1, n, angles);
}
// recursive function to label a single 600-cell vertex partition of the
// 120-cell by following icosahedral nets
// this doesn't work! completely - labels only 108-112
function label_120_partition_r(nodes, chords, label, origin, neighbours) {
console.log(`label_120_partition_r ${origin.id}`);
console.log(neighbours.map((n) => n.id).join(', '));
// first try to label everything
const unlabelled = [];
for( const n of neighbours ) {
if( n.label === 0 ) {
console.log(`Labelled ${n.id} ${label}`);
n.label = label;
unlabelled.push(n);
} else if( n.label !== label ) {
console.log(`node ${n.id} is already in group ${n.label}`);
//return false;
}
}
for( const n of unlabelled ) {
// the angles represent two icosahedral pyramids - partition them and
// pick the one which is at 60 to the edge we arrived on
//console.log(`looking for more neighbors for ${n}`);
const pairs60 = neighbour_angles(chords, n, "60.000");
const icosas = partition_nodes(pairs60);
const icosa = choose_icosa(nodes, origin, n, icosas);
const icosa_n = icosa_nodes(nodes, icosa);
console.log(`recursing to ${nice_icosa(nodes,icosa)}`);
return label_120_partition_r(nodes, chords, label, n, icosa_n);
}
}
// given a pair of icosa-sets, pick the one which is at the right angle to
// the incoming vector
function choose_icosa(nodes, origin, n1, icosas) {
for( const icosa of icosas ) {
const inodes = icosa_nodes(nodes, icosa);
const a60 = inodes.map((ni) => {
const a = THREE.MathUtils.radToDeg(vector_angle(n1, origin, ni));
return a.toFixed(3);
});
if( a60.filter((a) => a === "60.000").length > 0 ) {
return icosa;
}
}
console.log("No icosa found!");
return undefined;
}
function icosa_nodes(nodes, icosa) {
return Array.from(icosa).map((nid) => node_by_id(nodes, nid)).sort((a, b) => a.id - b.id);
}
function node_by_id(nodes, nid) {
const ns = nodes.filter((n) => n.id === nid);
return ns[0];
}
function enumerate_icosas(nodes) {
const chords = find_all_chords(nodes);
const chord3 = chords["1.74806"]; // these are edges of the 600-cells;
for( const n of nodes ) {
const pairs60 = neighbour_angles(chord3, n, "60.000");
const icosas = partition_nodes(pairs60);
for( const icosa of icosas ) {
const inodes = icosa_nodes(nodes, icosa);
console.log(icosa_to_csv(n.id, inodes).join(','));
}
}
}
function icosa_to_csv(nid, icosa) {
const cols = [ nid ];
const ia = icosa.map((n) => n.id);
for( let i = 1; i < 601; i++ ) {
if( ia.includes(i) ) {
cols.push(i);
} else {
cols.push('')
}
}
return cols;
}
function start_icosas(nodes, chords, origin) {
const pairs60 = neighbour_angles(chords, origin, "60.000");
return partition_nodes(pairs60).map((i) => nice_icosa(nodes, i));
}
function next_icosa(nodes, chords, origin, nid) {
const n = node_by_id(nodes, nid);
const pairs60 = neighbour_angles(chords, n, "60.000");
const icosas = partition_nodes(pairs60);
const icosa = choose_icosa(nodes, origin, n, icosas);
return nice_icosa(nodes, icosa);
}
function nice_icosa(nodes, icosa) {
return icosa_nodes(nodes, icosa).map((n) => n.id).join(', ');
}

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// New approach with tetrahedral coloring
function find_edges(links, nid) {
return links.filter((l) => l.source === nid || l.target === nid );
}
function find_adjacent(links, nid) {
return find_edges(links, nid).map((l) => {
if( l.source === nid ) {
return l.target;
} else {
return l.source;
}
});
}
function iterate_graph(nodes, links, n, fn) {
const queue = [];
const seen = {};
const nodes_id = {};
nodes.map((n) => nodes_id[n.id] = n);
queue.push(n.id);
seen[n.id] = true;
fn(n);
while( queue.length > 0 ) {
const v = queue.shift();
find_adjacent(links, v).map((aid) => {
if( !(aid in seen) ) {
seen[aid] = true;
queue.push(aid);
fn(nodes_id[aid]);
}
})
}
}
// stupid tetrahedral labelling
// keeps getting stuck
function naive_label_120cell(nodes, links, n) {
const nodes_id = {};
nodes.map((n) => nodes_id[n.id] = n);
iterate_graph(nodes, links, nodes[0], (n) => {
const cols = new Set();
const nbors = find_adjacent(links, n.id);
for( const nb of nbors ) {
if( nodes_id[nb].label > 0 ) {
cols.add(nodes_id[nb].label);
}
for( const nb2 of find_adjacent(links, nb) ) {
if( nb2 !== n.id && nodes_id[nb].label > 0 ) {
cols.add(nodes_id[nb2].label);
}
}
}
const pcols = [ 1, 2, 3, 4, 5 ].filter((c) => !cols.has(c));
if( pcols.length < 1 ) {
console.log(`Got stuck, no options at ${n.id}`);
return false;
} else {
n.label = pcols[0];
console.log(`found ${pcols.length} colors for node ${n.id}`);
console.log(`applied ${pcols[0]} to node ${n.id}`);
return true;
}
});
}