UnboundLocalError: local variable 'start' referenced before assignment

Dear Author: I just found an code logical bug in histogram. I think here should be raise an Exception.

def make_histogram(values, bins):
    """Convert values into a histogram proto using logic from histogram.cc."""
    values = values.reshape(-1)
    counts, limits = np.histogram(values, bins=bins)
    limits = limits[1:]
    # void Histogram::EncodeToProto in histogram.cc
    for i, c in enumerate(counts):
        if c > 0:
            start = max(0, i - 1)
            break

    for i, c in enumerate(reversed(counts)):
        if c > 0:
            end = -(i)
            break

    counts = counts[start:end]
    limits = limits[start:end]
    sum_sq = values.dot(values)
    return HistogramProto(min=values.min(),
                          max=values.max(),
                          num=len(values),
                          sum=values.sum(),
                          sum_squares=sum_sq,
                          bucket_limit=limits,
                          bucket=counts)

if all the elements in counts is 0 .there will be error like this:

File "/home/shuxiaobo/TR-experiments/cli/train.py", line 62, in train
    writer.add_histogram(name + '/grad', param.grad.clone().cpu().data.numpy(), j)
  File "/home/shuxiaobo/python3/lib/python3.6/site-packages/tensorboardX/writer.py", line 395, in add_histogram
    self.file_writer.add_summary(histogram(tag, values, bins), global_step, walltime)
  File "/home/shuxiaobo/python3/lib/python3.6/site-packages/tensorboardX/summary.py", line 142, in histogram
    hist = make_histogram(values.astype(float), bins)
  File "/home/shuxiaobo/python3/lib/python3.6/site-packages/tensorboardX/summary.py", line 162, in make_histogram
    counts = counts[start:end]
UnboundLocalError: local variable 'start' referenced before assignment

[yoonholee]

It turns out my values were NaN, I’ve fixed my bug. Still, it would have been helpful if the error message told me that the values being NaN was the problem.

[BPDanek]

It turns out my values were NaN, I’ve fixed my bug. Still, it would have been helpful if the error message told me that the values being NaN was the problem.

This is the exact issue I had. Thank you @yoonholee for the pointer, and yes I agree, there should be something indicating this. May be related to RL