#36 strage behavior of conditional statement

[GEN]

I have a simple 8x8 table initialized as follows:

0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1

Now I have the following (very simple) kernel, which has to convert
each 1 to a 2.

...
// Specifying the domain of execution for output stream
eucdist_saito_first_stage_fwd.domainOffset(uint4(0, 0, 0, 0));
eucdist_saito_first_stage_fwd.domainSize(uint4(width, 1, 1, 1)); // use 1
thread per row

// Perform the row scan forward
eucdist_saito_first_stage_fwd((float)width, inputStream, outputStream);

kernel void
eucdist_saito_first_stage_fwd(float width, float input[], out float output[])
{
float row = (float)(instance().x);
float j;

// Scan the row going forward
for(j = 0.0f; j<width; j=j+1.0f){

if(input[row*width + j] == 1.0f){
output[row*width + j] = 2.0f;
}
}
}

This simple code does not work !!! The "if" statement is always taken and the
output is:

2 2 2 2 2 2 2 2
2 2 2 2 2 2 2 2
2 2 2 2 2 2 2 2
2 2 2 2 2 2 2 2
2 2 2 2 2 2 2 2
2 2 2 2 2 2 2 2
2 2 2 2 2 2 2 2

However if I do:

kernel void
eucdist_saito_first_stage_fwd(float width, float input[], out float output[])
{
float row = (float)(instance().x);
float j;

// Scan the row going forward
for(j = 0.0f; j<width; j=j+1.0f){

if(input[row*width + j] == 1.0f){
output[row*width + j] = 2.0f * input[row*width + j];
}
}
}

I get:

0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
2 2 2 2 2 2 2 2
2 2 2 2 2 2 2 2
2 2 2 2 2 2 2 2
2 2 2 2 2 2 2 2

which makes no sense.

Forum URL : http://www.gpgpu.org/forums/viewtopic.php?t=5549