strain of PeriTriaxController

Hi，

1.When I saved the strain to TXT, I found that the strain was reset in the second compression.
  From -0.319026939509 changed to-0.000567920400817
 Maybe i misunderstand the meaning of O.cell.trsf=Matrix3.Identity

2.My idea is to change the first isotropic compression into an axial compression.How do i set the triax.goal and triax.stressMask?
  Maybe triax.goal=(-25000,-25000,-800000) triax.stressMask=4 triax.maxStrainRate=(0,0,0.5)

Thanks,

Feng

#################
# encoding: utf-8
from yade import pack, qt, plot
import matplotlib; matplotlib.rc('axes',grid=True)
import pylab

sigmaIso=-25000

O.periodic=True

spheres=O.materials.append(FrictMat(young=64e9,poisson=0.12,density=2650,frictionAngle=0.0005))
s=O.materials.append(FrictMat(young=64e9,poisson=0.12,density=2650,frictionAngle=0.24))

psdSizes,psdCumm=[0.01,.012,.015,.019,.020,.023,.027,.028,.030,.032,.033,.050],[0.0001,0.003,0.03,0.11,0.25,0.43,0.70,0.85,0.95,0.97,0.98,1]

sp=pack.SpherePack()
sp.makeCloud((0,0,0),(.2,.2,.2),psdSizes=psdSizes,psdCumm=psdCumm,distributeMass=True,periodic=True)
n=sp.toSimulation(material=spheres)

O.engines=[
   ForceResetter(),
   InsertionSortCollider([Bo1_Sphere_Aabb()]),
   InteractionLoop(
      [Ig2_Sphere_Sphere_ScGeom()],
      [Ip2_FrictMat_FrictMat_FrictPhys()],
      [Law2_ScGeom_FrictPhys_CundallStrack()]
   ),
   PeriTriaxController(label='triax',
      goal=(sigmaIso,sigmaIso,sigmaIso),stressMask=7,
      dynCell=True,maxStrainRate=(0.7,0.7,0.7),
      maxUnbalanced=1,relStressTol=0.05,
      doneHook='compactionFinished()'
   ),
   NewtonIntegrator(damping=.1),
   PyRunner(command='addPlotData()',iterPeriod=2000),
]

O.dt=1*PWaveTimeStep()
O.trackEnergy=True

def addPlotData():
 plot.addData(s0=triax.stress[0],s1=triax.stress[1],s2=triax.stress[2],
  x=triax.strain[0],y=triax.strain[1],z=triax.strain[2],
  q=triax.stress[2]-0.5*(triax.stress[0]+triax.stress[1]),
  p=(triax.stress[0]+triax.stress[1]+triax.stress[2])/3
 )

 plot.saveDataTxt('pq.txt.bz2',vars=('x'))

qt.View()
qt.Controller()
O.saveTmp()

def compactionFinished():
   for i in n:
        O.bodies[i].material = O.materials[s]
   O.cell.trsf=Matrix3.Identity
   triax.goal=(-800000,-800000,-800000)
   triax.stressMask=7
   triax.maxStrainRate=(0.5,0.5,0.5)
   triax.maxUnbalanced=10
   triax.doneHook='triaxFinished()'

def triaxFinished():
   print 'Finished'
   O.pause()