The codes below will show the difference. But why? Does that mean, cputime calculates the time for serial computation and tic--toc for parallel or SPMD(Single Process, Multiple Data)? When using SPMD, is the computation in parallel? And if you can use "top" in your server to monitor the cpu usage, you will see usage is more than 100%, that means you are using more than 1 cpu to calculate. Mine cpu usage was 1147%.
clc;
clear;
tic
t=cputime;
N=4000;
all=magic(N);
b=all*all*all*all*all*all*all;
cpu_time=cputime-t
toc_time=toc
============================
My running result is:
cpu_time =
167.3800
toc_time =
14.8073
Because the cpu usage is 1147% for me, so toc_time*1147% is almost the cpu_time result. So I think the cputime calculates the serial computation time.
