Strange performance for measuring time

Consider the following two code fragments, I try to measure the running time of func(dataMatrix, dim).

1st code fragment:

auto start_s=chrono::high_resolution_clock::now();

func(dataMatrix, dim);

auto end_s=chrono::high_resolution_clock::now();

double online_Time=(chrono::duration_cast<chrono::nanoseconds>(end_s-start_s).count());

2nd code fragment:

double**PP=new double*[n];
double*A=new double[n];

for(int i=0;i<n;i++)
    PP[i]=new double[dim];

delete[] A;
for(int i=0;i<n;i++)
    delete[] PP[i];

delete[] PP;

auto start_s=chrono::high_resolution_clock::now();

func(dataMatrix, dim);

auto end_s=chrono::high_resolution_clock::now();

double online_Time=(chrono::duration_cast<chrono::nanoseconds>(end_s-start_s).count());

After I measure the time, I find that the elapsed time of func(dataMatrix, dim) in 2nd code fragment is significantly (71x) slower than the 1st fragment.

I originally think that the elapsed time should be the same since the first 11 lines of the 2nd code fragment should not affect the elapsed time.

What is/are the reason(s) behind that?