hyunjimoon
commented
1 year ago As function block is only evaluated for 1,..,20 times, n_t should be (final time - initial time)/ time_step. In this sense, Tc over dt should be the main parameter.
vector vensim_ode_func(real time, vector outcome, real inventory_adjustment_time, real minimum_order_processing_time){
vector[7] dydt; // Return vector of the ODE function
// State variables
real work_in_process_inventory = outcome[1];
real expected_order_rate = outcome[2];
real production_rate_stocked = outcome[3];
real process_noise = outcome[4];
real backlog = outcome[5];
real inventory = outcome[6];
real production_start_rate_stocked = outcome[7];
real time_to_average_order_rate = 8;
real change_in_exp_orders = (dataFunc__customer_order_rate(time) - expected_order_rate) / time_to_average_order_rate;
real safety_stock_coverage = 2.01;
real desired_inventory_coverage = minimum_order_processing_time + safety_stock_coverage;
real wip_adjustment_time = 3.01;
real manufacturing_cycle_time = 6.01;
real desired_inventory = desired_inventory_coverage * expected_order_rate;
real adjustment_from_inventory = (desired_inventory - inventory) / inventory_adjustment_time;
real desired_production = fmax(0, expected_order_rate + adjustment_from_inventory);
real desired_wip = manufacturing_cycle_time * desired_production;
real adjustment_for_wip = (desired_wip - work_in_process_inventory) / wip_adjustment_time;
real process_noise_scale = 1;
real target_delivery_delay = 2.01;
real desired_shipment_rate = backlog / target_delivery_delay;
real process_noise_std_norm_data = 0.1;
real correlation_time = 10;
real maximum_shipment_rate = inventory / minimum_order_processing_time;
real order_fulfillment_ratio = lookupFunc__table_for_order_fulfillment(maximum_shipment_rate / desired_shipment_rate);
real shipment_rate = desired_shipment_rate * order_fulfillment_ratio;
real production_rate = fmax(0, 1 + process_noise) * work_in_process_inventory / manufacturing_cycle_time;
real time_step = 0.0625;
real production_rate_stocked_change_rate = (production_rate - production_rate_stocked) / time_step;
real desired_production_start_rate = desired_production + adjustment_for_wip;
real production_start_rate = fmax(0, desired_production_start_rate);
real production_start_rate_stocked_change_rate = production_start_rate - production_start_rate_stocked / time_step;
real reference_throughput = 170000;
real work_in_process_inventory_dydt = production_start_rate - production_rate;
real order_fulfillment_rate = shipment_rate;
real production_rate_stocked_dydt = production_rate_stocked_change_rate - production_rate;
real dt_tc = time_step / correlation_time;
real white_noise = process_noise_scale * process_noise_std_norm_data * (2 - dt_tc / dt_tc) ^ 0.5;
real process_noise_change_rate = (white_noise - process_noise) / correlation_time;
real process_noise_dydt = process_noise_change_rate;
real inventory_dydt = production_rate - shipment_rate;
real order_rate = dataFunc__customer_order_rate(time);
real expected_order_rate_dydt = change_in_exp_orders;
real backlog_dydt = order_rate - order_fulfillment_rate;
real production_start_rate_stocked_dydt = production_start_rate_stocked_change_rate - production_start_rate;
dydt[1] = work_in_process_inventory_dydt;
dydt[2] = expected_order_rate_dydt;
dydt[3] = production_rate_stocked_dydt;
dydt[4] = process_noise_dydt;
dydt[5] = backlog_dydt;
dydt[6] = inventory_dydt;
dydt[7] = production_start_rate_stocked_dydt;
print(production_rate);
return dydt;
}
real production_start_rate_stocked_change_rate = production_start_rate - production_start_rate_stocked / time_step;from function block of inventory model with process noise: is this evaluated 20 vs 20 * (1/0.0625) times?