NBPERF(1) | General Commands Manual | NBPERF(1) |
nbperf
—
nbperf |
[-ps ] [-a
algorithm] [-c
utilisation] [-h
hash] [-i
iterations] [-m
map-file] [-n
name] [-o
output] [input] |
nbperf
reads a number of keys one per line from standard
input or input. It computes a minimal perfect hash
function and writes it to stdout or output. The default
algorithm is “chm”.
The -m
argument instructs
nbperf
to write the resulting key mapping to
map-file. Each line gives the result of the hash
function for the corresponding input key.
The parameter utilisation determines the space efficiency.
Supported arguments for -a
:
Supported arguments for -h
:
The number of iterations can be limited with
-i
. nbperf
outputs a
function matching uint32_t
hash
(const void * restrict,
size_t) to stdout. The function expects the key length
as second argument, for strings not including the terminating NUL. It is the
responsibility of the caller to pass in only valid keys or compare the
resulting index to the key. The function name can be changed using
-n
name. If the
-s
flag is specified, it will be static.
After each failing iteration, a dot is written to stderr.
nbperf
checks for duplicate keys on the
first iteration that passed basic hash distribution tests. In that case, an
error message is printed and the program terminates.
If the -p
flag is specified, the hash
function is seeded in a stable way. This may take longer than the normal
random seed, but ensures that the output is the same for repeated
invocations as long as the input is constant.
nbperf
utility exits 0 on success,
and >0 if an error occurs.
September 25, 2012 | NetBSD 9.0 |