Chapter 4 Exercise

a. 4 warps per block b. 32 warps per grid (8 block per grid) c. i. for 40, [0,32), [32,64), two warps are active; for >=104, [96, 128), one warp is active; total 3 warps are active in a block; 3*8=24 warps are active in a grid ii. 2 warps are divergent iii. 100% iv. 8/32 = 25% v. (128-104)/32 = 75% d. i. 32 ii. 32 iii. 50% e. i. 3 ii. 2

  1. 2048
  2. 1
  3. max = 3.0; (1.0 + 0.7 + 0 + 0.2 + 0.6 + 1.1 + 0.4 + 0.1) / (8*3.0) = 17.08%
  4. bad idea. threads of a single warp could still out of sync.
  5. b

  6. a. 50% b. 50% c. 50% d. 100% e. 100%

  7. a. can get full occupancy. 16 blocks; 204830 = 61440 regs b. cannot get full occupancy. need 64 blocks but limited by 32 blocks per SM c. cannot get full occupancy. need 204834=69632 regs but limited by 65536 regs per SM

9. \(32 \times 32 = 1024 \text{ threads per block}\) but only 512 threads per block is allowed