NIST Test Suit- igamc: UNDERFLOW

Question

I used a 32-bit random number generator 100,000 times, and resulted in a file of 275,714 bytes. Then I typed the following line in my terminal,

./access 1024 (Here comes my first question, what should we exactly type here?) 

Then fed my file as input, then it come to

"How many bitstreams?" 269

Here 269( 269= 275,714/1024). And I chose Binary as my format. Finally, I got numerous lines of "igamc: UNDERFLOW". What should I cope with this?

Answer 1

NIST Test Suite can work on a number of bitstreams of certain length and its result can be then displayed as proportion of the bitstreams that passed test to all bitstreams (in finalAnalysisReport in Proportion column). So when you execute ./assess length, length is the length of one bitstream.

I think that igamc underflow can be caused by too short bitstreams. In NIST document, for every test recommended input size is specified and e.g. for Binary Matrix Rank Test it's somewhere close to 40 000 and for Overlapping Template Matching Test it's 1 000 000 and both of these tests use igamc function to compute P-value.