message: Increased error for acos.ispc test
diff: -bool ok(float x, float ref) { return (abs(x - ref) < 1e-6) || abs((x-ref)/ref) < 1e-6; }
  +bool ok(float x, float ref) { return (abs(x - ref) < 1e-4) || abs((x-ref)/ref) < 1e-4; }
  export void f_v(uniform float RET[]) {
  uniform float vals[8] = { 0, 1, 0.5, -1, -.87, -.25, 1e-3, -.99999999 };
  