Update microbenchmarks README and output format (#54)

* Update README to reflect the most result benchmark result.
* Update the HBM test output format for easier parsing.

Author: chishuen

microbenchmarks/README.md

@@ -55,7 +55,7 @@ python benchmark_hbm.py \
 
 Example output:
 ```
-Tensor size: 32.0 MBs, time taken (median): 0.0461 ms, bandwidth: 1454.54 GBps
+Tensor size (bytes): 33554432, time taken (ms, median): 0.049359414, bandwidth (GBps, median): 1359.5960438266143
 ```
 
 Run `python benchmark_hbm.py -h` to view the how to set the arguments.

microbenchmarks/benchmark_hbm.py

@@ -125,8 +125,8 @@ def main():
   bw_gbps = (tensor_size * 2) / result.time_median / 1e9  # read + write = 2
 
   print(
-      f"Tensor size: {tensor_size / 1024**2} MB, time taken (median):"
-      f" {result.time_median * 1000:.4f} ms, bandwidth: {bw_gbps:.2f} GBps"
+      f"Tensor size (bytes): {tensor_size}, time taken (ms, median):"
+      f" {result.time_median * 1000}, bandwidth (GBps, median): {bw_gbps} "
   )