鉴于一些
double x;
有什么区别
if((x>0 || (x<=0)))
和if(true)
?有什么区别吗?我认为它们是等效的,但似乎并非如此?有人知道为什么吗?
好的,我是 cpp 的新手,我很抱歉这个问题。但我确实需要解决这个问题 double sigmaX = 0.1; 双 sigmaY = 0.1;
SimPFilter::SimPFilter() {
totalParticles = 100;
nFilters = 2;
gsl_rng_env_setup();
rng = gsl_rng_alloc(gsl_rng_mt19937);
gsl_rng_set(rng, time(NULL));
}
SimPFilter::~SimPFilter() {
}
void SimPFilter::initParticles(double initX, gsl_rng* rng){
for (int i=0; i < totalParticles; i++) {
particles[i].xp = particles[i].x = 0.5 + gsl_ran_gaussian(rng, sigmaX*sigmaX);
if(i > totalParticles/2)
particles[i].xp = particles[i].x = -0.5 + gsl_ran_gaussian(rng, sigmaX*sigmaX);
particles[i].wNormalized = 1/(totalParticles/nFilters);
int j = (int)i/(totalParticles/nFilters);
particles[i].id = j;
filters[j].nParticles = (totalParticles/nFilters);
particles[i].w = particles[i].wp = particles[i].wNormalized = 1/totalParticles;
}
for(int i =0; i<nFilters; i++){
filters[i].weight = filters[i].weightPrev = 1.0/nFilters;
}
}
void SimPFilter::transition(gsl_rng* rng){
for (int i=0; i < totalParticles; i++) {
double temp = particles[i].x;
particles[i].xp = temp;
particles[i].x += gsl_ran_gaussian(rng, sigmaX*sigmaX); //the centre of each region
}
}
double SimPFilter::measure_prob(particle *p, double obser_y, gsl_rng* rng){
double x = p->x;
//cout << "x value is " << x << endl;
double prob = gsl_ran_gaussian_pdf (obser_y - (x*x), sigmaY);
//cout << "probability " << prob << endl;
std::cout << std::boolalpha;
//cout << (x>0 || (x<=0)) << endl;
if(true){
//cout << "probability2 " << prob << endl;
return prob;
}
return prob;
}
void SimPFilter::updateWeight(double obser_y, gsl_rng* rng){
for (int i=0; i < totalParticles; i++) {
double temp = particles[i].w;
particles[i].wp = particles[i].w;
particles[i].w = measure_prob(&particles[i], obser_y, rng);
}
//normalized particle weight
double eachFilterSum[nFilters];
for(int i=0; i < totalParticles; i++){
int id = particles[i].id;
eachFilterSum[id] += particles[i].w;
}
for(int i=0; i < totalParticles; i++){
particles[i].wNormalized = particles[i].w / eachFilterSum[particles[i].id];
}
//update each filter's weight
double eachFilterW[nFilters];
for(int i=0; i< totalParticles; i++){
//cout << "prticle i's weight1 "<<particles[i].w << endl;
int id = particles[i].id;
eachFilterW[id] += particles[i].wNormalized;
}
double sigmaweight =0; // simga pi n t-1 * wnt
for(int j=0; j<nFilters; j++){
sigmaweight += filters[j].weightPrev * eachFilterW[j];
}
for(int j=0; j<nFilters; j++){
double temp = filters[j].weight;
filters[j].weight = filters[j].weightPrev * eachFilterW[j] / sigmaweight;
filters[j].weightPrev = temp;
}
}
void SimPFilter::resample(gsl_rng* rng){
particle * newParticles;
newParticles = (particle*) malloc(totalParticles * sizeof(particle));
int index =(int)gsl_rng_uniform (rng)* totalParticles;
double beta = 0.0;
double maxWeight =0;
for (int i=0; i < totalParticles; i++) {
maxWeight = max(maxWeight, particles[i].wNormalized* filters[particles[i].id].weight);
}
for(int j=0; j < totalParticles; j++){
beta += (rng, 0, 2*maxWeight);
while(beta > particles[index].wNormalized * (filters[particles[index].id].weight)){
beta -= particles[index].wNormalized * (filters[particles[index].id].weight);
index = (index+1) % totalParticles;
}
newParticles[j] = particles[index];
}
for(int i=0; i<totalParticles; i++){
particles[i] = newParticles[i];
particles[i].w = particles[i].wNormalized = particles[i].wp =1/filters[particles[i].id].nParticles;
}
//update each filter particles number
vector<int> countP;
for(int i=0; i<nFilters; i++){
countP.push_back(0);
}
for(int i=0; i< totalParticles; i++){
countP.at(particles[i].id)++;
}
for(int i=0; i< nFilters; i++){
filters[i].nParticles = countP.at(i);
}
for(int i=0; i< nFilters;i++)
cout << "n particle value is " << filters[i].nParticles << endl;
free(newParticles);
}
` 在 measure_prob 函数中,我发现 if(true) 或 if(x>=0 || x<0) 给出不同的结果。当 if(true) 它可以跟踪两个对象,但是当我使用 if(x>=0 || x<0) 时,它会快速收敛到一个对象。我真的很困惑……