Compare the columns of data. For instance one might set it
        based on the input size  to create a table of the form:
                               | n=1 | n=4 | ...
                               ------------- ...
       ReLU(x + 1): (float)    | ... | ... | ...
       ReLU(x + 1): (int)      | ... | ... | ...

    using *Compare*. It is also included when printing a
    Measurement.

  * **env** (*Optional**[**str**]*) -- This tag indicates that
    otherwise identical tasks were run in different environments,
    and are therefore not equivalent, for instance when A/B
    testing a change to a kernel. *Compare* will treat
    Measurements with different *env* specification as distinct
    when merging replicate runs.

  * **num_threads** (*int*) -- The size of the PyTorch threadpool
    when executing *stmt*. Single threaded performance is
    important as both a key inference workload and a good
