(sort of) deterministic timing in Python

[mensanator at aol.com]

On Aug 13, 5:16 pm, johnmfis... at comcast.net (John Fisher) wrote:
> I am working on a framework for data acquisition in Python 2.5, am
> trying to get a structure going more like this:
>
> mark start time
> start event
>         event finishes
> count time until next interval
> start second event...
>
> rather than this:
>
> start event
>         event finishes
> sleep for interval
> start second event
>
> Do you see the difference? I get a true fixed interval from the first,
> including the time to accomplish the event task(s). In the second case,
> the sleep just gets tacked on at the end of the events, not very
> deterministic (timing-wise).
>
> So how do I accomplish this in Python with a minimum of labour?
>
> Thanks for any light you can shed on my darkness...
>
> wave_man

In the first example, you know when to start the second interval,
right? In the second case, you are assuming the second task is
ready to run after the sleep interval.

Here's an example that times how long an external program takes,
the os.popen() returns to the Python script when the external
C program completes, so no need for any sleep interval.

Because of the poorly written factor program, some composites
are falsely reported as unfactorable. This example keeps
re-calling the factor!.exe program until all composites are
factored or marked intractable, and the time to execute each
iteration of factor!.exe is printed after each call.


import os
import time

factor_program = 'factor! -d200 '

the_composites =
[['COMPOSITE_FACTOR','50818429800343305993022114330311033271249313957919046352679206262204589342623811236647989889145173098650749']]

the_primes = []
the_intractables = []

phase = 1
the_times = []
while the_composites:
  print "="*40
  print 'Phase',phase
  the_comp = the_composites.pop(0)
  print the_comp
  print
  the_times.append(time.time())  # time how long it takes to run
factor!.exe
  the_output = os.popen(factor_program+the_comp[1]).readlines()
  the_times.append(time.time())
  new_factors = [i.split() for i in the_output]
  for i in new_factors: print i
  print
  if len(new_factors) == 1:
    # it's prime or intractable
    if new_factors[0][0] == 'PRIME_FACTOR':
      the_primes.append([new_factors[0][0],long(new_factors[0][1])])
    else:
      the_intractables.append([new_factors[0][0],long(new_factors[0]
[1])])
    new_factors.pop()
  while new_factors:
    j = new_factors.pop(0)
    if j[0] == 'PRIME_FACTOR':
      the_primes.append([j[0],long(j[1])])
    else:
      the_composites.append(j)
  print the_times[phase] - the_times[phase-1],'seconds'
  phase += 1

print "="*40
print
print 'Factoring complete'
print

the_primes.sort()
the_intractables.sort()
the_primes.extend(the_intractables)

for i in the_primes:
  print i[0],i[1]
print
print "="*40

##  ========================================
##  Phase 1
##  ['COMPOSITE_FACTOR',
'50818429800343305993022114330311033271249313957919046352679206262204589342623811236647989889145173098650749']
##
##  ['PRIME_FACTOR', '37']
##  ['PRIME_FACTOR', '43']
##  ['PRIME_FACTOR', '167']
##  ['COMPOSITE_FACTOR', '507787751']
##  ['PRIME_FACTOR', '69847']
##  ['PRIME_FACTOR', '30697']
##  ['PRIME_FACTOR', '89017']
##  ['PRIME_FACTOR', '3478697']
##  ['PRIME_FACTOR', '434593']
##  ['PRIME_FACTOR', '49998841']
##  ['PRIME_FACTOR', '161610704597143']
##  ['PRIME_FACTOR', '14064370273']
##  ['COMPOSITE_FACTOR', '963039394703598565337297']
##  ['PRIME_FACTOR', '11927295803']
##
##  0.860000133514 seconds
##  ========================================
##  Phase 2
##  ['COMPOSITE_FACTOR', '507787751']
##
##  ['PRIME_FACTOR', '29819']
##  ['PRIME_FACTOR', '17029']
##
##  0.0780000686646 seconds
##  ========================================
##  Phase 3
##  ['COMPOSITE_FACTOR', '963039394703598565337297']
##
##  ['PRIME_FACTOR', '518069464441']
##  ['PRIME_FACTOR', '1858900129817']
##
##  0.0469999313354 seconds
##  ========================================
##
##  Factoring complete
##
##  PRIME_FACTOR 37
##  PRIME_FACTOR 43
##  PRIME_FACTOR 167
##  PRIME_FACTOR 17029
##  PRIME_FACTOR 29819
##  PRIME_FACTOR 30697
##  PRIME_FACTOR 69847
##  PRIME_FACTOR 89017
##  PRIME_FACTOR 434593
##  PRIME_FACTOR 3478697
##  PRIME_FACTOR 49998841
##  PRIME_FACTOR 11927295803
##  PRIME_FACTOR 14064370273
##  PRIME_FACTOR 518069464441
##  PRIME_FACTOR 1858900129817
##  PRIME_FACTOR 161610704597143
##
##  ========================================