code: function Population(opts) {
  
      // allow use object for gene
      var genes = opts.genes.map(function(gene, index) {
          return index;
      });
      this.oriGenes = opts.genes;
      this.fitness = function(individual) {
          individual = individual.map(function(geneIndex) {
              return opts.genes[geneIndex];
          });
          return opts.fitness(individual);
      };
  
      this.genePool = GenePool(genes, opts.N, opts.weights);
      this.K = opts.K;
      this.N = opts.N;
      // the very first generation
      this.population = [];
      this.history = {}; // 记住产生过的个体
  
      // 默认尝试1000次仍无新结果则取消尝试
      this.maxLoop = opts.maxLoop || 1000;
  
      this.birthRate = opts.birthRate;
      this.mutationRate = opts.mutationRate;
  }
docs: N: 个体基因数 K: 种群规模（种群稳定时的数量） genes: 基因 weights: 基因权重，影响出现的可能性大小 mutationRate: 基因突变率，大约有多少比例的基因需要突变 birthRate: 出生率 timeout: 最大时限