Require assistance parallelising a for loop within c#

i need someone who understands the problem and is able to help me solve it, while explaining the solution and the problem. please only message me if you have a solution to the problem, i dont have much time to waste. Request detail I currently have a c# application (.net) that i wish to parallelise, i have already attempted to parallelise it: the original for loop: for (ii = 0; ii < 2 * [login to view URL]((double)N / (double)wSamp) - 1; ii++) { for (jj = 0; jj < wSamp; jj++) { temp[jj] = x[ii * (wSamp / 2) + jj]; } tempFFT = fft(temp); for (kk = 0; kk < wSamp / 2; kk++) { Y[kk][ii] = (float)[login to view URL](tempFFT[kk]); if (Y[kk][ii] > fftMax) { fftMax = Y[kk][ii]; } } } my attempt at parallelising it: [login to view URL] (0, 2 * (int)[login to view URL]((double)n / (double)wsamp) - 1, ii => { for (jj = 0; jj < wsamp; jj++) { temp[jj] = x[ii * (wsamp / 2) + jj]; } tempfft = fft(temp); for (kk = 0; kk < wsamp / 2; kk++) { y[kk][ii] = (float)[login to view URL](tempfft[kk]); if (y[kk][ii] > fftmax) { fftmax = y[kk][ii]; } } }) ; However, while this code compiles it gives me a run time error saying 'index out of loop' for the y component. I'm assuming the issue is due to the y array and parallelising not being compatible with arrays. the full function is as follows: float[][] stft(Complex[] x, int wSamp) { //int ii = 0; int ll = 0; int kk = 0; int jj = 0; int N = [login to view URL]; float fftMax = 0; float[][] Y = new float[wSamp / 2][]; Complex[] temp = new Complex[wSamp]; Complex[] tempFFT = new Complex[wSamp]; for (ll = 0; ll < wSamp / 2; ll++) { Y[ll] = new float[2 * N / wSamp]; } for (ii = 0; ii < 2 * [login to view URL]((double)N / (double)wSamp) - 1; ii++) { for (jj = 0; jj < wSamp; jj++) { temp[jj] = x[ii * (wSamp / 2) + jj]; } tempFFT = fft(temp); for (kk = 0; kk < wSamp / 2; kk++) { Y[kk][ii] = (float)[login to view URL](tempFFT[kk]); if (Y[kk][ii] > fftMax) { fftMax = Y[kk][ii]; } } } for (int ii = 0; ii < 2 * [login to view URL]((double)N / (double)wSamp) - 1; ii++) { for (kk = 0; kk < wSamp / 2; kk++) { Y[kk][ii] /= fftMax; } } return Y; }