94 lines
3.3 KiB
Python
94 lines
3.3 KiB
Python
#!/usr/bin/env python
|
|
##
|
|
## Name: findthreshold.py
|
|
## Purpose: Find a good threshold for recursive multiplication.
|
|
## Author: M. J. Fromberger
|
|
##
|
|
## This tool computes some timing statistics to help you select a suitable
|
|
## recursive multiplication breakpoint. It uses the imtimer tool to run a
|
|
## series of tests varying precision and breakpoint, and prints out a summary
|
|
## of the "best" values for each category. Each summary line contains the
|
|
## following fields, tab-separated:
|
|
##
|
|
## prec -- the precision of the operands (in digits).
|
|
## thresh -- the threshold for recursive multiplication (digits).
|
|
## trec -- total time using recursive algorithm (sec).
|
|
## tnorm -- total time without recursive algorithm (sec).
|
|
## ratio -- speedup (ratio of tnorm/trec).
|
|
##
|
|
## You are responsible for reading and interpreting the resulting table to
|
|
## obtain a useful value for your workload. Change the default in imath.c, or
|
|
## call mp_int_multiply_threshold(n) during program initialization, to
|
|
## establish a satisfactory result.
|
|
##
|
|
import math, os, random, sys, time
|
|
|
|
|
|
def get_timing_stats(num_tests, precision, threshold, seed=None):
|
|
"""Obtain timing statistics for multiplication.
|
|
|
|
num_tests -- number of tests to run.
|
|
precision -- number of digits per operand.
|
|
threshold -- threshold in digits for recursive multiply.
|
|
seed -- random seed; if None, the clock is used.
|
|
|
|
Returns a tuple of (seed, bits, time) where seed is the random seed used,
|
|
bits is the number of bits per operand, and time is a float giving the
|
|
total time taken for the test run.
|
|
"""
|
|
if seed is None:
|
|
seed = int(time.time())
|
|
|
|
line = os.popen(
|
|
'./imtimer -mn -p %d -t %d -s %d %d' % (precision, threshold, seed,
|
|
num_tests), 'r').readline()
|
|
|
|
count, prec, bits, thresh, status = line.strip().split('\t')
|
|
kind, total, unit = status.split()
|
|
|
|
return seed, int(bits), float(total)
|
|
|
|
|
|
def check_binary(name):
|
|
if not os.path.exists(name):
|
|
os.system('make %s' % name)
|
|
if not os.path.exists(name):
|
|
raise ValueError("Unable to build %s" % name)
|
|
elif not os.path.isfile(name):
|
|
raise ValueError("Path exists with wrong type")
|
|
|
|
|
|
def compute_stats():
|
|
check_binary('imtimer')
|
|
seed = int(time.time())
|
|
|
|
print >> sys.stderr, "Computing timer statistics (this may take a while)"
|
|
stats = {}
|
|
for prec in (32, 40, 64, 80, 128, 150, 256, 384, 512, 600, 768, 1024):
|
|
sys.stderr.write('%-4d ' % prec)
|
|
stats[prec] = (None, 1000000., 0.)
|
|
|
|
for thresh in xrange(8, 65, 2):
|
|
s, b, t = get_timing_stats(1000, prec, thresh, seed)
|
|
sp, bp, tp = get_timing_stats(1000, prec, prec + 1, seed)
|
|
|
|
if t < stats[prec][1]:
|
|
stats[prec] = (thresh, t, tp)
|
|
sys.stderr.write('+')
|
|
else:
|
|
sys.stderr.write('.')
|
|
sys.stderr.write('\n')
|
|
|
|
return list((p, h, t, tp) for p, (h, t, tp) in stats.iteritems())
|
|
|
|
|
|
if __name__ == "__main__":
|
|
stats = compute_stats()
|
|
stats.sort(key=lambda s: s[3] / s[2])
|
|
for prec, thresh, trec, tnorm in stats:
|
|
print "%d\t%d\t%.3f\t%.3f\t%.4f" % (prec, thresh, trec, tnorm,
|
|
tnorm / trec)
|
|
|
|
print
|
|
|
|
# Here there be dragons
|