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update fnv_tool.cal about no FNV primes for some sizes.

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FNV primes for bit size powers of 2  > 1024 are extremely rare.
There are no FNV primes for bit size powers of 2 >= 2048 and <= 1048576.
This commit is contained in:
Landon Curt Noll
2023-07-31 13:35:50 -07:00
parent 3148ce06a0
commit 9fcdd80549
1 changed files with 4 additions and 5 deletions
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cal/fnv_tool.cal
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@@ -65,8 +65,8 @@
* *
* NOTE: For n that is a power of 2 and n > 1024, you will find that * NOTE: For n that is a power of 2 and n > 1024, you will find that
* that FNV primes become so rare that that one may not find a suitable * that FNV primes become so rare that that one may not find a suitable
* FNV prime. For n = 2048, 4096, 8192, 16384, 32768, 65536, 131072 * FNV prime. For n = powers of 2 >= 2048 and <= 1048576,
* 262144, and 524288, there is NO suitable FNV prime. * there is NO FNV primes.
* *
* As for as hashing goes, large values of n, even if an * As for as hashing goes, large values of n, even if an
* FNV hash may be found, are unlikely to be truly useful. :-) * FNV hash may be found, are unlikely to be truly useful. :-)
@@ -173,10 +173,9 @@ define find_fnv_prime(bits)
if (interactive) { if (interactive) {
if (popcnt(bits) == 1) { if (popcnt(bits) == 1) {
if (bits > 1024) { if (bits > 1024) {
print "# WARNING: FNV primes for powers of 2 > 1024 are extremely rare."; print "# WARNING: FNV primes for bit size powers of 2 > 1024 are extremely rare.";
print "# WARNING: There are no FNV primes for 2048, 4096, 8192, 16384, 327678, 65536, 131072, 262144, nor 524288."; print "# WARNING: There are no FNV primes for bit size powers of 2 >= 2048 and <= 1048576.";
} }
print "# NOTE: bits a power of 2 and bits >= 32: bits is suitable for a true FNV hash";
print "n =", bits; print "n =", bits;
} else { } else {
if (bits < 32) { if (bits < 32) {