I made few little scripts to work with .sim checkpoint files. Before, I just deleted them manually. Now I have few hotkeys. The toolset is intended for long sims with keyframed behavior. Now I work on an animation for a dancer performance, which is ~ 7200 frames. I plan to update the scripts asap ... to reset multiple related DOPs (pops driven by pyro etc.) with one hotkey press.

The script contains os.remove(file_path), so check it before use.

• reset the sim, hotkey: F5
  delete all the .sim cache files in the playrange
  but don't delete the first one, I want to built on it
  sim_cache_reset ()
  sim_cache_delete_playrange ()

• trim the playback range start to the playhead's precedent .sim file
  hotkey: /
  playrange_to_precedent ()

• add or remove one .sim spacing in playrange
  hotkeys: . ,
  playrange_extend_spacing (direction)

import os
import hou
import math
import bisect
import toolutils


#####################
###     resim     ###
#####################

# return the current dopnet node
def sim_dopnet () :
    dopnet = hou.currentDopNet()
    if dopnet == None :
        cache_on       = 0
        cache_name     = None
        cache_substeps = 1
        cache_start    = 1
        cache_spacing  = 1
    else :
        cache_on       = dopnet.parm("explicitcache").eval()
        cache_name     = dopnet.parm("explicitcachename").rawValue()
        cache_substeps = dopnet.parm("substep").eval()
        cache_start    = dopnet.parm("startframe").eval()
        cache_spacing  = dopnet.parm("explicitcachecheckpointspacing").eval()
    return [dopnet, cache_on, cache_name, cache_substeps, cache_start, cache_spacing]


# list of all $SF that may be cached with current dopnet settings
# and list of appropriate $F frames
def sim_cache_framelists() :
    dopnet, cache_on, cache_name, cache_substeps, cache_start, cache_spacing = sim_dopnet()
    framerange_end = hou.playbar.frameRange()[1]

    candidate_sf = 0
    candidate_f  = cache_start
    list_sf      = [candidate_sf]
    list_f       = [candidate_f]

    while candidate_f <= framerange_end :
        candidate_sf  += cache_spacing
        candidate_f   = math.floor((candidate_sf-1) / cache_substeps) + cache_start
        list_sf.append(candidate_sf) 
        list_f.append (candidate_f) 

    return list_sf, list_f


# find the given frame's precedent cached $F
def sim_cache_precedent_index ( frame ) :
    list_sf, list_f = sim_cache_framelists()
    precedent_index = bisect.bisect_right(list_f,frame)
    precedent_index = max (precedent_index - 1, 0)
    return precedent_index


# delete the .sim cache files in the playrange
# but don't delete the first one, we want to built on it
def sim_cache_delete_playrange () :
    dopnet, cache_on, cache_name, cache_substeps, cache_start, cache_spacing = sim_dopnet()
    hou.cd(dopnet.path()) # to expandString() correctly
    list_sf, list_f = sim_cache_framelists()
    index = 1 + sim_cache_precedent_index(  hou.playbar.playbackRange()[0]  )

    candidate_frames = list_sf[index:]
    
    # try to delete the files, if they exist
    for frame in candidate_frames :
        file_path = cache_name.replace("$SF",str(frame))
        file_path = hou.expandString(file_path)
        file_path = file_path.replace("*","_")

        if file_path.endswith(".sim") :
            try :
                os.remove(file_path)
            except :
                frame_was_not_cached = 1


# hotkey: F5
# reset the sim
def sim_cache_reset () :
    dopnet, cache_on, cache_name, cache_substeps, cache_start, cache_spacing = sim_dopnet()

    if cache_on:
        # delete .sim files
        message = "Delete .sim files in playback range? \n\n" + str(dopnet.path())
        if hou.ui.displayMessage(message, buttons=("OK", "Cancel")) == 0:
            sim_cache_delete_playrange()

    if dopnet:
        dopnet.parm("resimulate").pressButton()

    hou.setFrame(hou.playbar.playbackRange()[0]) 


# hotkey: /
# trim the playback start to the playhead's precedent cached .sim file
def playrange_to_precedent () :
    list_sf, list_f = sim_cache_framelists()
    index = sim_cache_precedent_index(  hou.intFrame()  )

    frame_start = list_f[index]
    frame_end   = hou.playbar.playbackRange()[1]
    hou.playbar.setPlaybackRange( frame_start, frame_end )


# hotkeys: . ,
# add or remove one cached spacing in playrange
def playrange_extend_spacing (direction) :
    list_sf, list_f = sim_cache_framelists()
    index = sim_cache_precedent_index(  hou.playbar.playbackRange()[0]  )
    index = max (index + direction, 0)

    frame_start = list_f[index]
    frame_end   = hou.playbar.playbackRange()[1]
    hou.playbar.setPlaybackRange( frame_start, frame_end )


#####################
###   resim end   ###
#####################