Strange GLSL behavior - opengl

Question

I'm trying to implement tonemap correction in my own graphic engine and I'm using, as reference, the excellent demo from asylum2010 (https://github.com/asylum2010/Asylum_Tutorials)
Now look: this is an adaptation of the shader taken from the aforesaid demo:
#version 150
uniform sampler2D sampler0;
uniform vec2 texelSize;
uniform int prevLevel;
in vec2 tex;
out vec4 my_FragColor0;
void main()
{
const vec3 LUMINANCE_VECTOR = vec3(0.2125, 0.7154, 0.0721);
vec4 sample = texture(sampler0, tex + vec2(-0.5, -0.5) * texelSize);
float dt = dot(sample.rgb, LUMINANCE_VECTOR);
if (sample.r > 0.99 && sample.g > 0.99 && sample.b > 0.99)
{
if (dt > 0.9998)
{
if (log(0.0001 + dt) < 1.0) // <== NOTICE THIS!
my_FragColor0 = vec4(0.1, 0.0, 0.0, 1.0);
else
my_FragColor0 = vec4(1.0, 0.0, 0.0, 1.0);
}
else
my_FragColor0 = vec4(0.0, 0.0, 0.0, 1.0);
}
else
my_FragColor0 = vec4(0.0, 0.0, 0.0, 1.0);
}
and this is the shader I wrote:
#version 150
uniform sampler2D ColorMap;
uniform vec2 TexelSize;
uniform int PreviousLevel;
in vec2 fragmentUV;
out vec4 fragment;
void main()
{
const vec3 LUMINANCE_VECTOR = vec3(0.2125, 0.7154, 0.0721);
vec4 sample = texture(ColorMap, fragmentUV + vec2(-0.5, -0.5) * TexelSize);
float dt = dot(sample.rgb, LUMINANCE_VECTOR);
if (sample.r > 0.99 && sample.g > 0.99 && sample.b > 0.99)
{
if (dt > 0.9998)
{
if (log(0.0001 + dt) < 1.0) // <== NOTICE THIS!
fragment = vec4(0.1, 0.0, 0.0, 1.0);
else
fragment = vec4(1.0, 0.0, 0.0, 1.0);
}
else
fragment = vec4(0.0, 0.0, 0.0, 1.0);
}
else
fragment = vec4(0.0, 0.0, 0.0, 1.0);
}
You may notice that, except for the variable names, the code is exactly the same.
Now when I run the first shader on its own engine, it outputs a full red color for almost white pixels of the passed sampler is almost white (r, g and b > 0.99), meaning the result of the log calculation is greater than 1.0
When I run my own shader (of course passing the same sample and with the same texel size), it outputs a dark red, meaning the log result is lower than 1.0.
It looks to me that the result of the second shader is correct but this is not the point. The point is: how coult the result be different?

Answer 1

Ok for the ones interested I finally found the issue.
The error is actually the dot product. I was passing as ColorMap a texture with internal format GL_RGBA while it is supposed to be a floating point texture in order to store values higher than 1.
Also I would like to know the reason of the downvote I received. Knowing the reason will help me to avoid any mistake I possibly made posting the question.