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[zhou qian <question680215@xxxxxxxxxxxxxxxxxxxxx>]

New question #680215 on Yade:
https://answers.launchpad.net/yade/+question/680215

Hi:
I defined a periotric cell and found that in the first step, the trsf didn't change.
Here are the codes, 
import libyade

from libyade import*
from libyade import utils, pack, Matrix3, Vector3, Vector3
import datetime

def randomPeriPack(radius,initSize,seed):
	O.switchScene(); O.resetThisScene()
	sp=pack.SpherePack()
	O.periodic=True
	O.cell.setBox(initSize)
	sp.makeCloud(Vector3().Zero,O.cell.refSize,radius,0.,-1,True,seed=seed)
	O.engines=[
		ForceResetter(),
		InsertionSortCollider([Bo1_Sphere_Aabb()],verletDist=.05*radius),
		InteractionLoop(
			[Ig2_Sphere_Sphere_ScGeom()],
			[Ip2_FrictMat_FrictMat_FrictPhys()],
			[Law2_ScGeom_FrictPhys_CundallStrack()]),
		PeriIsoCompressor(charLen=2*radius,stresses=[-100e9,-1e8],maxUnbalanced=1e-2,doneHook='O.pause();',globalUpdateInt=20,keepProportions=True),
		NewtonIntegrator(damping=.8)
	]
	O.materials.append(FrictMat(young=30e9,frictionAngle=.1,poisson=.3,density=1e3))
	for s in sp: O.bodies.append(utils.sphere(s[0],s[1]))
	O.dt=utils.PWaveTimeStep()
	O.timingEnabled=True
	O.run(); O.wait()
	for b in O.bodies: b.state.pos = O.cell.wrap(b.state.pos)
	ret=pack.SpherePack()
	ret.fromSimulation()
	O.switchScene()
	return ret

O.materials.append(FrictMat(young=5e8,frictionAngle=.6,poisson=.3,density=1e7))
sp = randomPeriPack(.01,.1*Vector3.Ones,10)
sp.toSimulation()
O.engines = [
	ForceResetter(),
	InsertionSortCollider([Bo1_Sphere_Aabb(aabbEnlargeFactor=1.5,label='is2aabb')],allowBiggerThanPeriod=True),
	InteractionLoop(
		[Ig2_Sphere_Sphere_ScGeom(interactionDetectionFactor=1.5,label='ss2d3dg')],
		[Ip2_FrictMat_FrictMat_FrictPhys()],
		[Law2_ScGeom_FrictPhys_CundallStrack()]),
	NewtonIntegrator(damping=.2),
]
O.dt = 0.0002
#O.step()
is2aabb.aabbEnlargeFactor = 1.
ss2d3dg.interactionDetectionFactor = 1.

dstrain = Matrix3(0,0,0,0,0,0,0,0,-0.002)
trsf1 = O.cell.trsf
I = Matrix3.Identity
trsf2 = dstrain + I
print(trsf2)

O.cell.velGrad = dstrain/100/O.dt

O.step()
print(O.cell.trsf)
O.step()
print(O.cell.trsf)

I think the second output should be (1,0,0,0,1,0,0,0,0.99998),
but the second output is (1,0,0,0,1,0,0,0,0.99998) and the trsf starts to change in the next O.step()
1.What happend in the first O.step()?
2.If I use O.run(5), it only run 4 steps?

Yours,
Joe

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