code: function(lamda) {
              var xNext = []
              for (i = 0; i < dimension; i++) {
                  xNext[i] = self.x[i] + lamda * self.p[i]
              }
              return self.f(xNext)
          }
docs: ////////////////////////////////////////////////////////////// 2. lineSearch: min f(x + lamda * p) 搜索步长 done: stepsize