examples: add performance benchmark with matlab

Author: AldoGl

examples/benchmark_w_matlab.jl

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+
+# # Comparing the performance of the Julia and MATLAB implementations
+
+# We can compare the performance of the Julia and MATLAB implementations by running the same model for the same number of epochs and measuring the time taken.
+
+using BeforeIT, Plots, Statistics
+
+parameters = BeforeIT.AUSTRIA2010Q1.parameters
+initial_conditions = BeforeIT.AUSTRIA2010Q1.initial_conditions
+T = 12*2 
+
+# We will run the model without any output to avoid the overhead of printing the results.
+function run_no_output(;multi_threading = false)
+    model = BeforeIT.initialise_model(parameters, initial_conditions, T)
+    data = BeforeIT.initialise_data(model);
+    
+    for _ in 1:T
+        BeforeIT.one_epoch!(model; multi_threading = multi_threading)
+        BeforeIT.update_data!(data, model)
+    end
+end
+
+# we run the code to compile it fist
+@time run_no_output() 
+@time run_no_output(;multi_threading = true) 
+
+# time taken by the MATLAB code, computed independently on an Apple M1 chip
+matlab_times = [3.1465, 3.0795, 3.0274, 3.0345, 3.0873]
+matlab_time = mean(matlab_times)
+matlab_time_std = std(matlab_times)
+
+# time taken by the Julia code, computed as the average of 5 runs
+n_runs = 5
+
+julia_times_1_thread = zeros(n_runs)   
+for i in 1:n_runs
+    julia_times_1_thread[i] = @elapsed run_no_output()
+end
+julia_time_1_thread = mean(julia_times_1_thread)
+julia_time_1_thread_std = std(julia_times_1_thread)
+
+
+julia_times_multi_thread = zeros(n_runs)
+for i in 1:5
+    julia_times_multi_thread[i] =  @elapsed run_no_output(multi_threading = true)
+end
+julia_time_multi_thread = mean(julia_times_multi_thread)
+julia_time_multi_thread_std = std(julia_times_multi_thread)
+
+# get the number of threads used
+n_threads = Threads.nthreads()
+
+# bar chart of the time taken vs the time taken by the MATLAB code, also plot the stds as error bars
+bar(["MATLAB", "Julia, 1 thread", "Julia, $n_threads threads"], [matlab_time, julia_time_1_thread, julia_time_multi_thread], yerr = [matlab_time_std, julia_time_1_thread_std, julia_time_multi_thread_std], legend = false, dpi=300)
+ylabel!("Time for one simulation (s)")
+
+# the Julia implementation is faster than the MATLAB implementation, and the multi-threaded version is faster than the single-threaded version.
+
+# save the image
+savefig("benchmark_w_matlab.png")