My Particle Swarm Optimization code generates different answers in C++ and MATLAB - c++

Question

I have written a global version of Particle Swarm Optimization algorithm in C++.
I tried to write it exactly as same as my MATLAB PSO code that have written before, but this code generates different and so worst answers.
The MATLAB code is:
clear all;
numofdims = 30;
numofparticles = 50;
c1 = 2;
c2 = 2;
numofiterations = 1000;
V = zeros(50, 30);
initialpop = V;
Vmin = zeros(30, 1);
Vmax = Vmin;
Xmax = ones(30, 1) * 100;
Xmin = -Xmax;
pbestfits = zeros(50, 1);
worsts = zeros(50, 1);
bests = zeros(50, 1);
meanfits = zeros(50, 1);
pbests = zeros(50, 30);
initialpop = Xmin + (Xmax - Xmin) .* rand(numofparticles, numofdims);
X = initialpop;
fitnesses = testfunc1(X);
[minfit, minfitidx] = min(fitnesses);
gbestfit = minfit;
gbest = X(minfitidx, :);
for i = 1:numofdims
Vmax(i) = 0.2 * (Xmax(i) - Xmin(i));
Vmin(i) = -Vmax(i);
end
for t = 1:1000
w = 0.9 - 0.7 * (t / numofiterations);
for i = 1:numofparticles
if(fitnesses(i) < pbestfits(i))
pbestfits(i) = fitnesses(i);
pbests(i, :) = X(i, :);
end
end
for i = 1:numofparticles
for j = 1:numofdims
V(i, j) = min(max((w * V(i, j) + rand * c1 * (pbests(i, j) - X(i, j))...
+ rand * c2 * (gbest(j) - X(i, j))), Vmin(j)), Vmax(j));
X(i, j) = min(max((X(i, j) + V(i, j)), Xmin(j)), Xmax(j));
end
end
fitnesses = testfunc1(X);
[minfit, minfitidx] = min(fitnesses);
if(minfit < gbestfit)
gbestfit = minfit;
gbest = X(minfitidx, :);
end
worsts(t) = max(fitnesses);
bests(t) = gbestfit;
meanfits(t) = mean(fitnesses);
end
In which, testfunc1 is:
function [out] = testfunc1(R)
out = sum(R .^ 2, 2);
end
The C++ code is:
#include <cstring>
#include <iostream>
#include <cmath>
#include <algorithm>
#include <ctime>
#define rand_01 ((float)rand() / (float)RAND_MAX)
const int numofdims = 30;
const int numofparticles = 50;
using namespace std;
void fitnessfunc(float X[numofparticles][numofdims], float fitnesses[numofparticles])
{
memset(fitnesses, 0, sizeof (float) * numofparticles);
for(int i = 0; i < numofparticles; i++)
{
for(int j = 0; j < numofdims; j++)
{
fitnesses[i] += (pow(X[i][j], 2));
}
}
}
float mean(float inputval[], int vallength)
{
int addvalue = 0;
for(int i = 0; i < vallength; i++)
{
addvalue += inputval[i];
}
return (float)(addvalue / vallength);
}
void PSO(int numofiterations, float c1, float c2,
float Xmin[numofdims], float Xmax[numofdims], float initialpop[numofparticles][numofdims],
float worsts[], float meanfits[], float bests[], float *gbestfit, float gbest[numofdims])
{
float V[numofparticles][numofdims] = {0};
float X[numofparticles][numofdims];
float Vmax[numofdims];
float Vmin[numofdims];
float pbests[numofparticles][numofdims];
float pbestfits[numofparticles];
float fitnesses[numofparticles];
float w;
float minfit;
int minfitidx;
memcpy(X, initialpop, sizeof(float) * numofparticles * numofdims);
fitnessfunc(X, fitnesses);
minfit = *min_element(fitnesses, fitnesses + numofparticles);
minfitidx = min_element(fitnesses, fitnesses + numofparticles) - fitnesses;
*gbestfit = minfit;
memcpy(gbest, X[minfitidx], sizeof(float) * numofdims);
for(int i = 0; i < numofdims; i++)
{
Vmax[i] = 0.2 * (Xmax[i] - Xmin[i]);
Vmin[i] = -Vmax[i];
}
for(int t = 0; t < 1000; t++)
{
w = 0.9 - 0.7 * (float) (t / numofiterations);
for(int i = 0; i < numofparticles; i++)
{
if(fitnesses[i] < pbestfits[i])
{
pbestfits[i] = fitnesses[i];
memcpy(pbests[i], X[i], sizeof(float) * numofdims);
}
}
for(int i = 0; i < numofparticles; i++)
{
for(int j = 0; j < numofdims; j++)
{
V[i][j] = min(max((w * V[i][j] + rand_01 * c1 * (pbests[i][j] - X[i][j])
+ rand_01 * c2 * (gbest[j] - X[i][j])), Vmin[j]), Vmax[j]);
X[i][j] = min(max((X[i][j] + V[i][j]), Xmin[j]), Xmax[j]);
}
}
fitnessfunc(X, fitnesses);
minfit = *min_element(fitnesses, fitnesses + numofparticles);
minfitidx = min_element(fitnesses, fitnesses + numofparticles) - fitnesses;
if(minfit < *gbestfit)
{
*gbestfit = minfit;
memcpy(gbest, X[minfitidx], sizeof(float) * numofdims);
}
worsts[t] = *max_element(fitnesses, fitnesses + numofparticles);
bests[t] = *gbestfit;
meanfits[t] = mean(fitnesses, numofparticles);
}
}
int main()
{
time_t t;
srand((unsigned) time(&t));
float xmin[30], xmax[30];
float initpop[50][30];
float worsts[1000], bests[1000];
float meanfits[1000];
float gbestfit;
float gbest[30];
for(int i = 0; i < 30; i++)
{
xmax[i] = 100;
xmin[i] = -100;
}
for(int i = 0; i < 50; i++)
for(int j = 0; j < 30; j++)
{
initpop[i][j] = rand() % (100 + 100 + 1) - 100;
}
PSO(1000, 2, 2, xmin, xmax, initpop, worsts, meanfits, bests, &gbestfit, gbest);
cout<<"fitness: "<<gbestfit<<endl;
return 0;
}
I have debugged two codes many times but can not find the difference which makes answers different.
It is making me crazy!
May you help me please?
Update:
Please consider that, the function mean is just used for reporting some information and is not used in the optimization procedure.

Answer 1

You've got integer division in the following line
w = 0.9 - 0.7 * (float) (t / numofiterations);
w will be 0.2 for every iteration, change it to
w = 0.9 - 0.7 * t / numofiterations;
The first multiplication will automatically promote t to a double the division should then promote numof iterations to a double.
The parenthesis means it will be done first and therefore not be promoted as wo integers is involved in the division.

Answer 2

This could be a mistake in function mean:
return (float)(addvalue / vallength);
This is integer division, so the result is truncated down, then cast to float. It is unlikely this is what you want.