cocos2d-x 2.0 iOS fragment shader inconsistent between simulator and device

cocos2d-x C++
#1

I have a fragment shader that does something like this:

#ifdef GL_ES
precision lowp float;
#endif

varying vec2 v_texCoord;
uniform sampler2D u_texture;
uniform float u_time;

void main(void)
{
    //sample the color
    vec4 sampledcolor = texture2D(u_texture, v_texCoord);

    //convert to hsv
    vec3 color = ConvertRGBToHSV(sampledcolor.rgb);

    //hue modification
    color.r = mod((color.r + (u_time * 0.1)), 1.0);

    //convert back to rgb
    color = ConvertHSVToRGB(color);

    //set the final color
    gl_FragColor = vec4(color.r,color.g,color.b,sampledcolor.a);
}

Where the functions ConvertRGBtoHSV and ConvertHSVToRGB do the proper color conversions. When the shader is applied in the iPhone simulator the hue cycle is correct. When the shader is applied on the actual iPhone4 device, the color doesn’t appear to cycle the same and also doesn’t continue after the first cycle. It almost seems as if the mod() isn’t happening on the device.

Anyone have any ideas what could be going wrong here?

platform: iOS
XCode version: 4.3.1
target: iphone4
cocos2d-x: cocos2d-2.0-rc2-x-2.0.1

#2

This wound up being a precision thing. I changed to:

precision highp float;

The device then worked just like the simulator.