difference gradient

#include <math.h> #include <stdlib.h>#include <stdio.h>void show_vector(float *A, int n) {    for (int i = 0; i < n; i++) {            printf("%2.5f \t", A[i]);    }    printf("\n");}float func( float* x ){    float result = 0.0;    result = x[0] * x[0] * x[0] + x[1] *x[1];    return result;}/*  Calculating gradient of a function with different methods*/void forward(){   int n = 2;   float x[] = { 0, 0};   float pf[] = { 0, 0};   float dx = 0.001;   float f = func( x );   for( int i = 0; i < n; i++ )   {       x[i] += dx;       float newF = func( x );       float diff = newF - f;       pf[i] = diff/dx;       x[i] -= dx;    }   printf( "forward pf =  \n" );   show_vector( pf, n );}void twoside(){   int n = 2;   float x[] = { 0, 0};   float pf[] = { 0, 0};   float dx = 0.01;   float f = func( x );   for( int i = 0; i < n; i++ )   {       x[i] += dx;       float F_forward = func( x );       x[i] -= 2*dx;        float F_backward = func( x );       x[i] += dx;       float diff = F_forward - F_backward ;       pf[i] = diff/(2*dx);   }   printf( "two side pf =  \n" );   show_vector( pf, n );}void fourthorder(){   int n = 2;   float x[] = { 0, 0};   float pf[] = { 0, 0};   float dx = 0.01;   float f = func( x );   for( int i = 0; i < n; i++ )   {       float x0 = x[i];       x[i] = x0 + dx;       float F_forward_1 = func( x );       x[i] = x0 + 2*dx;       float F_forward_2 = func( x );       x[i] = x0 - dx;        float F_backward_1 = func( x );       x[i] = x0 - 2*dx;        float F_backward_2 = func( x );       x[i] = x0;       float diff = 2* F_forward_2 + 16*F_forward_1 - 16 F_backward_1 - 2* F_backward_2 ;       pf[i] = diff/(4*dx);   }   printf( "fourth order pf =  \n" );   show_vector( pf, n );   }void main(){    forward();    twoside();    fourthorder();    return;}