On November 11, 1988, Patterson called and said that the run was finished.
Always careful, he proposed to verify that there was a record of each
subcase before sending the results on a magnetic tape back to us. Somehow,
the news of the end the plane of order 10 was spread around the
combinatorics community and we were deluged with inquiries. On November
18, Patterson called again with some bad news. There was an error number 4
for one of the A2's. What is an error number 4? It had been two years
since we last looked at our CRAY program. Taking out an old listing, it
took us a while to determine that error number 4 was a size problem for a
data structure that could not be enlarged. This A2 could not be solved
with the existing CRAY program! If it had been able to handle this A2,
it would have taken about 30 seconds. The only other program around that
could handle this case was our slow but adaptable NPL program. After
further dividing this A2 into about 200 smaller subcases, it took NPL
one day to solve one of them, giving an estimate of 200 days just to solve
this A2! Meanwhile, Barry Cipra from Science called and said he would
like to write an article about the non-existence of a plane of order 10.
What should we tell everybody?
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