  double   a     3*{100, 200} = 0 / 2.2
        step 0: 
          block 0: [ 0:99,   0:199] = 0 / 2
        step 1: 
          block 0: [ 0:99,   0:199] = 0.1 / 2.1
        step 2: 
          block 0: [ 0:99,   0:199] = 0.2 / 2.2
  float    b     3*{100} = 0 / 2.2
        step 0: 
          block 0: [ 0:99] = 0 / 2
        step 1: 
          block 0: [ 0:99] = 0.1 / 2.1
        step 2: 
          block 0: [ 0:99] = 0.2 / 2.2
