my_tree_is_too_big;_what_should_I_do?

I've seen a few instances of people suffering in silence (or worse, proclaiming that MeqTrees are too slow/too memory-hungry for their needs) when their trees are suboptimal by orders of magnitude... It's a (mostly social) problem that worries me and I have no idea how to solve it yet.

What this means is - don't suffer in silence! Ask a question! A MeqTrees guru may be able to help you.

For example, Oleg pointed out that the following script could be sped up (tests showed by a factor of about 20) by changing the order of operations (which allows us to eliminate the time-expensive Compounder node). Trace out the sequence of operations when the pre_rotate' flag is set to True (the script will run very quickly) vs what is done when pre-rotate' is set to False.

# a script to generate a sequence of CLAR beam images as a# function of time. # The original script is available as Timba/WH/contrib/AGW/MG_AGW_clar_beam.py# from Timba.TDL import *from Timba.Meq import meqfrom Timba.Meq import meqdsfrom make_multi_dim_request import *import Meow.Bookmarks# setup a few bookmarksSettings.forest_state = record(bookmarks=[  Meow.Bookmarks.PlotPage("CLAR Beam",[[beam_rot]],[[AzEl]])]);# Timba.TDL.Settings.forest_state is a standard TDL name.# This is a record passed to Set.Forest.State.Settings.forest_state.cache_policy = 100;# get position of field centre RA DECTDLCompileMenu('Field Centre RA and DEC',  TDLOption('fc_ra','RA of field centre (radians)',[0,1,2,3],more=float),  TDLOption('fc_dec','DEC of field centre (radians)',[0,1,2,3],more=float),);# get telescope location for use in simulationTDLCompileOption('telescope','Telescope Site',['DRAO','VLA'])# do fast or slow calculationTDLCompileOption('pre_rotate','Pre-Rotate L and M frame (fast method)',[True, False])def _define_forest (ns):  """define_forest() is a standard TDL name. When a forest script is  loaded by, e.g., the browser, this method is automatically called to  define the forest. The 'ns' argument is a NodeScope object in which  the forest is to be defined, usually this is simply the global scope.  """;# we  build up the mathematical expression of a CLAR power# pattern using the formulae# log16 =  (-1.0) * log(16.0)# L,M give direction cosines wrt field centre in# AzEl coordinate frame# L_gain = (L * L) / (width * width)# sin_factor = sqr(sin(field centre elevation))# M_gain = (sin_factor * M * M ) / (width * width)# power pattern = exp(log16 * (L_gain + M_gain))# constant used in beam calculation  ns.ln_16 << Meq.Constant(-2.7725887)# CLAR HPBW of 3 arcmin at zenith = 0.00087266 radians  ns.HPBW << Meq.Constant(0.00087266)# beam is centred in L,M grid  ns.centre << Meq.Constant(0.0)# create a MeqComposer containing ra dec position  ns.RADec <<Meq.Composer(fc_ra, fc_dec)# we create an AzEl node with an Observatory name  ns.AzEl << Meq.AzEl(radec=ns.RADec, observatory=telescope)# create a Parallactic angle node  pa = ns.ParAngle << Meq.ParAngle(radec=ns.RADec, observatory = telescope)# rotation matrix to go from AzEl to Ra,Dec L,M  ns.P << Meq.Matrix22(Meq.Cos(pa),-Meq.Sin(pa),Meq.Sin(pa),Meq.Cos(pa))# get the elevation  ns.El << Meq.Selector(ns.AzEl, index=1)# get sine of elevation - used to get CLAR  beam broadening  ns.sine_el << Meq.Sin(ns.El)  # square this sine value  ns.sine_el_sq << Meq.Sqr(ns.sine_el)# create L and M axis nodes  laxis = ns.laxis << Meq.Grid(axis=2);  maxis = ns.maxis << Meq.Grid(axis=3);# attempt to de-rotate the beam in AzEl coordinates to sky coordinates  if pre_rotate:    ns.lm_pre_rot << Meq.Composer(laxis,maxis)    # returns an lm 2-vector    ns.rot_lm << Meq.MatrixMultiply(ns.P,ns.lm_pre_rot);    # rotated lm    ns.l_rot << Meq.Selector(ns.rot_lm,index=0)    ns.m_rot << Meq.Selector(ns.rot_lm,index=1)    ns.l_sq << Meq.Sqr(ns.l_rot - ns.centre)    ns.m_sq << Meq.Sqr(ns.m_rot - ns.centre)    ns.m_sq_sin << Meq.Multiply(ns.m_sq, ns.sine_el_sq)# Add l and m gains    ns.l_and_m_sq << Meq.Add(ns.l_sq, ns.m_sq_sin)    ns.beam_rot << Meq.Exp((ns.l_and_m_sq * ns.ln_16) / Meq.Sqr(ns.HPBW))  else:    ns.l_sq << Meq.Sqr(laxis - ns.centre)    ns.m_sq << Meq.Sqr(maxis - ns.centre)    ns.m_sq_sin << Meq.Multiply(ns.m_sq, ns.sine_el_sq)# Add l and m gains    ns.l_and_m_sq << Meq.Add(ns.l_sq, ns.m_sq_sin)    ns.exp_gain << Meq.Exp((ns.l_and_m_sq * ns.ln_16) / Meq.Sqr(ns.HPBW))# attempt to de-rotate the beam in AzEl coordinates to sky coordinates    ns.lm_pre_rot << Meq.Composer(laxis,maxis)    # returns an lm 2-vector    ns.rot_lm << Meq.MatrixMultiply(ns.P,ns.lm_pre_rot);    # rotated lm    ns.l_rot << Meq.Selector(ns.rot_lm,index=0)    ns.m_rot << Meq.Selector(ns.rot_lm,index=1)    ns.lm_rot << Meq.Composer(Meq.Grid(axis=0),Meq.Grid(axis=1),ns.l_rot,ns.m_rot)    ns.resampler << Meq.Resampler(ns.exp_gain,dep_mask = 0xff)    ns.beam_rot << Meq.Compounder(children=[ns.lm_rot,ns.resampler],common_axes=[hiid('l'),hiid('m')])##################################################def _test_forest (mqs,parent,wait=False):  """test_forest() is a standard TDL name. When a forest script is  loaded by, e.g., the browser, and the "test" option is set to true,  this method is automatically called after define_forest() to run a  test on the forest. The 'mqs' argument is a meqserver proxy object.  """;# any large time range will do: we observe the changes in the beam# pattern in timesteps of 2400s, or 40 min  delta_t = 2400.0  # Approx start of 2001  t0 = 4485011731.14 - delta_t  t1 = t0 + delta_t# here, any frequency range will do  f0 = 800.0  f1 = 1300.0  m_range = [-0.0025,0.0025];  l_range = [-0.0025,0.0025];  lm_num = 31;  counter = 0  for i in range(12):    t0 = t0 + delta_t    t1 = t0 + delta_t    request = make_multi_dim_request(counter=counter, dom_range = [[f0,f1],[t0,t1],l_range,m_range], nr_cells = [1,1,lm_num,lm_num])    counter = counter + 1# execute request    mqs.meq('Node.Execute',record(name='beam_rot',request=request),wait=False);##################################################if __name__=='__main__':  ns=NodeScope()  _define_forest(ns)  ns.Resolve()  print "Added %d nodes" % len(ns.AllNodes())```