Thank you L. Spiro

Kindly help me to fix below compile error,

Fragment shader compile log: ERROR: 0:1: 'gl_FragCoord' : syntax error: syntax error

// MODIFIED FRAGMENT SHADER CODE AS BELOW
precision highp gl_FragCoord;
//precision highp vec4 gl_FragCoord;

void main() 
{
 ....
}

And putting below didn't make any difference to the program

precision highp float;

Please help

It was an issue in the following line.

if(mod(xpos, 2.0) == 0.0)

Seems highp values beyond 2048 mod operation returns values where equals operation fails in the above condition.

I did the following and it seems fine in the iPad pro also

int val = int(mod(gl_FragCoord.x, 2.0));

if(val == 0)
  gl_FragColor = // red;
else
  gl_FragColor = // green;

Thanks you all