def test_VB_compression_plain_docids(IFfilename):
'''
Tests the performance of VB codes using plain docIds.
'''
int_bytes = calculate_int_bytes_of_IF(IFfilename)
all_postings_docids = flatten(get_postings_list_ints(open(IFfilename).readlines()))
t = time.time()
bytelists = ic.vb_encode(all_postings_docids)
t2 = time.time() - t
flattened = flatten(bytelists)
# since every entry in the flattened list is 8 bits long, the number of
# used bytes is exactly the length of the flattened list
compressed_bytes = len(flattened)
t = time.time()
ic.vb_decode(bytelists)
t3 = time.time() - t
print 'VB-encdoing: using plain doc ids'
print '-------------------------------'
print '# of IDs to compress: ' + str(len(all_postings_docids))
print 'Uncompressed (bytes): ' + str(int_bytes)
print 'Compressed (bytes): ' + str(compressed_bytes)
print 'Compression factor: ' + str(float(int_bytes) / float(compressed_bytes))
print 'Time to compress (s): ' + str(t2)
print 'Time to decompress (s): ' + str(t3)
print '==================================='
def test_VB_compression_gaps_docids(IFfilename):
'''
Tests the performance of VB codes using gaps.
'''
int_bytes = calculate_int_bytes_of_IF(IFfilename)
lines = open(IFfilename).readlines()
int_lists = get_postings_list_ints(lines)
gap_lists = get_gaps_from_int_lists(int_lists)
all_postings_gapids = flatten(gap_lists)
t = time.time()
bytelists = ic.vb_encode(all_postings_gapids)
t2 = time.time() - t
flattened = flatten(bytelists)
compressed_bytes = len(flattened)
t = time.time()
ic.vb_decode(bytelists)
t3 = time.time() - t
print 'VB-encoding: using gaps instead of plain doc ids'
print '-----------------------------------------------'
print '# of IDs to compress: ' + str(len(all_postings_gapids))
print 'Uncompressed (bytes): ' + str(int_bytes)
print 'Compressed (bytes): ' + str(compressed_bytes)
print 'Compression factor: ' + str(float(int_bytes) / float(compressed_bytes))
print 'Time to compress (s): ' + str(t2)
print 'Time to decompress (s): ' + str(t3)
print '==================================='