I have a variable that changes with train iterations. The variable is not computed as a part of the computational graph.
Is it possible to add it to the tensorflow summary in order to visualize it together with the loss function?
Yes, you can create summaries outside the graph.
Here is an example where the summary is created outside the graph (not as a TF op):
output_path = "/tmp/myTest"
summary_writer = tf.summary.FileWriter(output_path)
for x in range(100):
myVar = 2*x
summary=tf.Summary()
summary.value.add(tag='myVar', simple_value = myVar)
summary_writer.add_summary(summary, x)
summary_writer.flush()