"Uncaught ReferenceError: glpk is not defined" even after local loading

[lbreal]

Hello,

I am facing a problem with GLPK.js. Even after downloading the glpk.min.js file and including it locally in my project, I keep getting the error "Uncaught ReferenceError: glpk is not defined".

My HTML code is as follows:
<

<script src="glpk.min.js" defer></script> <script> document.addEventListener('DOMContentLoaded', function() { glpk.then(glpk => { // Inicialize o GLPK.js antes de usá-lo console.log("GLPK.js loaded successfully.");

    // Definindo o problema de transporte
    const supply = [20, 30, 25]; // Fornecimento de cada fornecedor
        const demand = [10, 25, 20, 20]; // Demanda de cada consumidor

        // Custos de transporte
        const costs = [
            [8, 6, 10, 9],  // Custos do fornecedor 1
            [9, 12, 13, 7], // Custos do fornecedor 2
            [14, 9, 16, 5]  // Custos do fornecedor 3
        ];

        // Função para resolver o problema de transporte usando GLPK.js
        function solveTransportationProblem(supply, demand, costs) {
            const numSuppliers = supply.length;
            const numConsumers = demand.length;

            // Variáveis de decisão e a função objetivo
            let variables = [];
            let objective = [];
            for (let i = 0; i < numSuppliers; i++) {
                for (let j = 0; j < numConsumers; j++) {
                    let varName = `x_${i}_${j}`;
                    variables.push(varName);
                    objective.push({ name: varName, coef: costs[i][j] });
                }
            }

            // Restrições de fornecimento
            let constraints = [];
            for (let i = 0; i < numSuppliers; i++) {
                let constraint = { name: `supply_${i}`, vars: [], bnds: { type: glpk.GLP_UP, ub: supply[i], lb: supply[i] } };
                for (let j = 0; j < numConsumers; j++) {
                    constraint.vars.push({ name: `x_${i}_${j}`, coef: 1 });
                }
                constraints.push(constraint);
            }

            // Restrições de demanda
            for (let j = 0; j < numConsumers; j++) {
                let constraint = { name: `demand_${j}`, vars: [], bnds: { type: glpk.GLP_UP, ub: demand[j], lb: demand[j] } };
                for (let i = 0; i < numSuppliers; i++) {
                    constraint.vars.push({ name: `x_${i}_${j}`, coef: 1 });
                }
                constraints.push(constraint);
            }

            // Configuração do problema
            let problem = {
                name: 'Transportation Problem',
                objective: {
                    direction: glpk.GLP_MIN,
                    name: 'obj',
                    vars: objective
                },
                subjectTo: constraints
            };

            // Resolver o problema usando GLPK.js
            let solution = glpk.solve(problem);

            // Extrair a matriz de alocação e o custo total
            let allocation = Array.from({ length: numSuppliers }, () => Array(numConsumers).fill(0));
            for (let varName in solution.result.vars) {
                let [_, i, j] = varName.split('_').map(Number);
                allocation[i][j] = solution.result.vars[varName];
            }
            let totalCost = solution.result.z;

            return { allocation, totalCost };
        }

        // Resolvendo o problema de transporte
        const solution = solveTransportationProblem(supply, demand, costs);
        console.log("Solution:", solution);
        alert(`Custo total de transporte: ${solution.totalCost}`);

        // Exibir matriz de alocação
        console.log("Allocation matrix:", solution.allocation);


  }); 
});

</script>

[jvail]

Hi,

here is a minimal example: https://github.com/jvail/glpk.js/blob/master/examples/lp.html If you adjust your import/script then it should work out of the box.

[lbreal]

Thanks for answering!

I'm still encountering difficulties using GLPK.js in my local development environment, even after trying different approaches. Here are the issues I'm facing:

Approach 1: Local File Import ( import GLPK from '../dist/index.js';)
I'm unable to import GLPK.js as a module from a local file.

The error in console is:
Access to script at 'file:///C:/Users/luiza/Documents/Documentos/PO/jogos/meu_jogo/glpk.min.js' from origin 'null' has been blocked by CORS policy: Cross origin requests are only supported for protocol schemes: http, data, isolated-app, chrome-extension, chrome, https, chrome-untrusted.

Approach 2: CDN Import ( import GLPK from 'https://cdn.jsdelivr.net/npm/[email protected]/dist/glpk.min.js';)

When I try to import GLPK.js as a module from a CDN, I get a different error:
Uncaught SyntaxError: The requested module 'https://cdn.jsdelivr.net/npm/[email protected]/dist/glpk.min.js' does not provide an export named 'default' (at teste.html:6:16)

The code used is the following:

<title>Optimal Transportation Problem with GLPK.js</title> <script type="module"> import GLPK from '../dist/index.js'; (async () => {

        const glpk = await GLPK();

        function print(res) {
            const el = window.document.getElementById('out');
            el.innerHTML = `Solution: Transportation Problem\n\n ${JSON.stringify(res, null, 2)}`;
        };

        // Definindo o problema de transporte
        const supply = [20, 30, 25]; // Fornecimento de cada fornecedor
        const demand = [10, 25, 20, 20]; // Demanda de cada consumidor

        // Custos de transporte
        const costs = [
            [8, 6, 10, 9],  // Custos do fornecedor 1
            [9, 12, 13, 7], // Custos do fornecedor 2
            [14, 9, 16, 5]  // Custos do fornecedor 3
        ];

        const numSuppliers = supply.length;
        const numConsumers = demand.length;

        // Variáveis de decisão e a função objetivo
        let variables = [];
        for (let i = 0; i < numSuppliers; i++) {
            for (let j = 0; j < numConsumers; j++) {
                variables.push({ name: `x_${i}_${j}`, coef: costs[i][j] });
            }
        }

        // Restrições de fornecimento
        let constraints = [];
        for (let i = 0; i < numSuppliers; i++) {
            let vars = [];
            for (let j = 0; j < numConsumers; j++) {
                vars.push({ name: `x_${i}_${j}`, coef: 1 });
            }
            constraints.push({ name: `supply_${i}`, vars: vars, bnds: { type: glpk.GLP_FX, ub: supply[i], lb: supply[i] } });
        }

        // Restrições de demanda
        for (let j = 0; j < numConsumers; j++) {
            let vars = [];
            for (let i = 0; i < numSuppliers; i++) {
                vars.push({ name: `x_${i}_${j}`, coef: 1 });
            }
            constraints.push({ name: `demand_${j}`, vars: vars, bnds: { type: glpk.GLP_FX, ub: demand[j], lb: demand[j] } });
        }

        // Configuração do problema
        const lp = {
            name: 'Transportation Problem',
            objective: {
                direction: glpk.GLP_MIN,
                name: 'obj',
                vars: variables
            },
            subjectTo: constraints
        };

        const opt = {
            msglev: glpk.GLP_MSG_OFF
        };

        // Resolver o problema usando GLPK.js
        const solution = await glpk.solve(lp, opt);
        print(solution);

        console.log(await glpk.solve(lp, glpk.GLP_MSG_DBG));

        window.document.getElementById('cplex').innerHTML = await glpk.write(lp);

    })();
</script>

Optimal Transportation Problem with GLPK.js

[jvail]

The error in console is:
Access to script at 'file:///C:/Users/luiza/Documents/Documentos/PO/jogos/meu_jogo/glpk.min.js' from origin 'null' has been blocked by CORS policy: Cross origin requests are only supported for protocol schemes: http, data, isolated-app, chrome-extension, chrome, https, chrome-untrusted.

Yes, that is normal. If you want to develop locally I propose to use serve. That is what I do as well:

1. Clone this repo
2. Create your html/js files somewhere in the repo folder
3. Run npx serve
4. Navigate to your file in the browser e.g. http://localhost:3000/examples/lp