int bnum = 0;
  buf[tid] = in[idx];
  barrier(CLK_LOCAL_MEM_FENCE);
  for (int i = 1; i < dim; i*=2) {
    bnum = 1 - bnum;
    if (tid >= i) {
      buf[bnum*dim+tid] = buf[(1-bnum)*dim+tid] + buf[(1-bnum)*dim+tid-i];
    } else {
      buf[bnum*dim+tid] = buf[(1-bnum)*dim+tid];
    }
    barrier(CLK_LOCAL_MEM_FENCE);
  }
  out[idx] = buf[bnum*dim+tid];
  barrier(CLK_LOCAL_MEM_FENCE);
  if (tid == 0) {
    if (dim < n) {
      bout[gid] = buf[dim-1];
    } else {
      bout[gid] = buf[n-1];
    }
  }

the problematic output:

116: cpu=58 gpu=58
117: cpu=59 gpu=59
118: cpu=60 gpu=60
119: cpu=60 gpu=60
120: cpu=60 gpu=60
121: cpu=61 gpu=61
122: cpu=61 gpu=61
123: cpu=62 gpu=62
124: cpu=62 gpu=62
125: cpu=62 gpu=62
126: cpu=62 gpu=62
127: cpu=62 gpu=62
128: cpu=63 gpu=26
129: cpu=64 gpu=27
130: cpu=64 gpu=27
131: cpu=65 gpu=28
132: cpu=66 gpu=29
133: cpu=67 gpu=30
134: cpu=68 gpu=31
135: cpu=69 gpu=32
136: cpu=70 gpu=33
137: cpu=71 gpu=34
138: cpu=71 gpu=34
139: cpu=72 gpu=35
140: cpu=72 gpu=35
141: cpu=73 gpu=36