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Performance tweaks
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In practice this does not make the solver much faster: the presolve eliminates most of these variables already
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@domdomegg
domdomegg committed Jan 30, 2024
1 parent 2c762b2 commit 3f28d48
Showing 1 changed file with 70 additions and 48 deletions.
118 changes: 70 additions & 48 deletions lib/scheduler.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -26,8 +26,8 @@ export interface Cohort {
people: { [personType: string]: string[] },
}

const toBinary = (personType: PersonType, person: Person, t: number): string => JSON.stringify([personType.name, person.id, t.toString()]);
const fromBinary = (binary: string): [string, string, string] => JSON.parse(binary);
const toBinary = (personType: PersonType, person: Person, t: number): string => JSON.stringify([personType.name, person.id, t]);
const fromBinary = (binary: string): [string, string, number] => JSON.parse(binary);

const getCohortCount = (t: number): string => `cohortCount-${t}`;

Expand Down Expand Up @@ -67,58 +67,71 @@ export async function solve({ lengthOfMeeting, personTypes }: SchedulerInput): P
// array from 0 to maxT
const times = Array.from({ length: maxT }, (_, i) => i);

// VARIABLES
const cohortCounts: string[] = [];
for (const t of times) {
cohortCounts.push(getCohortCount(t));
}

const binaries: string[] = [];
for (const personType of personTypes) {
for (const person of personType.people) {
for (const t of times) {
binaries.push(toBinary(personType, person, t));
const isAvailable = person.timeAv.some(
([b, e]) => b <= t && t <= e - lengthOfMeeting
)
if (isAvailable) {
const u = toBinary(personType, person, t);
binaries.push(u);
}
}
}
}

const cohortCounts: string[] = [];
for (const t of times) {
cohortCounts.push(getCohortCount(t));
}

const assignmentConstraints: LP["subjectTo"] = [];
const availabilityConstraints: LP["subjectTo"] = [];
const nonOverlappingConstraints: LP["subjectTo"] = [];
for (const personType of personTypes) {
for (const person of personType.people) {
const personBinaries: string[] = [];
for (const t of times) {
const u = toBinary(personType, person, t);
personBinaries.push(u);

availabilityConstraints.push({
name: u + "-availability",
vars: [{ name: u, coef: 1 }],
bnds: {
type: glpk.GLP_UP,
ub: person.timeAv.some(
([b, e]) => b <= t && t <= e - lengthOfMeeting
)
? 1
: 0,
lb: 0,
},
});
const isAvailable = person.timeAv.some(
([b, e]) => b <= t && t <= e - lengthOfMeeting
)
if (isAvailable) {
const u = toBinary(personType, person, t);
personBinaries.push(u);
availabilityConstraints.push({
name: u + "-availability",
vars: [{ name: u, coef: 1 }],
bnds: {
type: glpk.GLP_UP,
ub: 1,
lb: 0,
},
});

const meetingVars: string[] = [];
for (let i = 0; i < lengthOfMeeting; i++) {
meetingVars.push(toBinary(personType, person, t + i));
// No need to not overlap if only scheduling one cohort
if (person.howManyCohorts > 1) {
const meetingVars: string[] = [];
for (let i = 0; i < lengthOfMeeting; i++) {
const u = toBinary(personType, person, t + i)
if (binaries.includes(u)) {
meetingVars.push(u);
}
}
if (meetingVars.length >= 2) {
nonOverlappingConstraints.push({
name: u + "-non-overlapping",
vars: meetingVars.map((u) => ({ name: u, coef: 1 })),
bnds: {
type: glpk.GLP_UP,
ub: 1,
lb: 0,
},
});
}
}
}
nonOverlappingConstraints.push({
name: u + "-non-overlapping",
vars: meetingVars.map((u) => ({ name: u, coef: 1 })),
bnds: {
type: glpk.GLP_UP,
ub: 1,
lb: 0,
},
});
}

assignmentConstraints.push({
Expand All @@ -132,7 +145,7 @@ export async function solve({ lengthOfMeeting, personTypes }: SchedulerInput): P
const cohortCountConstraints: LP["subjectTo"] = [];
for (const t of times) {
for (const personType of personTypes) {
const personBinaries = personType.people.map(person => toBinary(personType, person, t));
const personBinaries = personType.people.map(person => toBinary(personType, person, t)).filter(b => binaries.includes(b));

cohortCountConstraints.push({
name: personType.name + "-" + t + "-max",
Expand All @@ -153,20 +166,20 @@ export async function solve({ lengthOfMeeting, personTypes }: SchedulerInput): P
}
}

const constraints = [
const constraints = ([
...assignmentConstraints,
...availabilityConstraints,
...nonOverlappingConstraints,
...cohortCountConstraints,
];
]);

try {
const res = await glpk.solve(
{
name: "eh?",
name: "scheduler",
objective: {
direction: glpk.GLP_MAX,
name: "eh2?",
name: "max_scheduled_sessions",
vars: binaries.map((u) => ({ name: u, coef: 1 })),
},
subjectTo: constraints,
Expand All @@ -176,20 +189,20 @@ export async function solve({ lengthOfMeeting, personTypes }: SchedulerInput): P
options
);

/* PROCESS RESULT
[{ people: { Participant: [id, ...], Facilitator: [id, ...] }
time: number }, ...] */
const timeslots = {};
/* PROCESS RESULT */
const timeslots: Record<number, Record<PersonType['name'], Person['id'][]>> = {};
for (const binary of Object.keys(res.result.vars)) {
if (binary.includes("cohortCount")) continue;
if (binary.includes("cohortCount")) {
continue;
}
const [personType, person, t] = fromBinary(binary);
if (res.result.vars[binary] == 1) {
if (!timeslots[t]) timeslots[t] = {};
if (!timeslots[t][personType]) timeslots[t][personType] = [];
timeslots[t][personType].push(person);
}
}

const largeCohorts: Cohort[] = [];
for (const t of Object.keys(timeslots)) {
largeCohorts.push({
Expand Down Expand Up @@ -240,3 +253,12 @@ export async function solve({ lengthOfMeeting, personTypes }: SchedulerInput): P
return null;
}
}

const shuffle = <T>(array: T[]): T[] => {

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'shuffle' is assigned a value but never used
const arrayCopy = array.slice();
for (let i = arrayCopy.length - 1; i > 0; i--) {
const j = Math.floor(Math.random() * (i + 1));
[arrayCopy[i], arrayCopy[j]] = [arrayCopy[j], arrayCopy[i]];
}
return arrayCopy;
}

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