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authorMattias Andrée <maandree@kth.se>2016-03-01 10:55:20 +0100
committerMattias Andrée <maandree@kth.se>2016-03-01 10:55:20 +0100
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+.TH ZPTEST 3 libzahl
+.SH NAME
+zptest - Test the primality of a big integer
+.SH SYNOPSIS
+.nf
+#include <zahl.h>
+
+enum zprimality zptest(z_t \fIwitness\fP, z_t \fIquestioned\fP, z_t \fItries\fP);
+.fi
+.SH DESCRIPTION
+.B zptest
+tests whether
+.I questioned
+is a prime number. This is implemented using the
+Miller–Rabin primality test.
+.P
+If
+.I questioned
+is determined to be a composite, the witness if its
+compositeness is stored into
+.I witness
+unless
+.I witness
+is
+.BR 0 .
+.BR zgcd (3)
+can be used on
+.I questioned
+and
+.I witness
+to extract a factor of
+.IR questioned .
+This factor can be either composite, prime, or 1.
+.P
+The risk that a composite number is determined to be
+a probably prime is
+.IR (1-4↑-tries) .
+.SH RETURN VALUE
+This function will either return:
+.TP
+.B NONPRIME
+.I questioned
+is certainly a composite number.
+.TP
+.B PROBABLY_PRIME
+.I questioned
+is probably a prime number.
+.TP
+.B PRIME
+.I questioned
+is certainly a prime number.
+.SH NOTES
+If
+.I questioned
+is less than two
+.I questioned
+is copied into
+.P
+Increasing
+.I tries
+only reduces the chance that
+.B PROBABLY_PRIME
+is returned. It cannot increase
+the chance that
+.B PRIME
+is returned.
+.IR witness .
+.SH SEE ALSO
+.BR zgcd (3)