[sage-support] Multiprocessing for Tensors is not working for Macintosh. (SageMath 9.0)

['Alan Stafford' via sage-support]

Multiprocessing of Tensors is not working for Macintosh.

show(version())
#MacBook Pro dual core i5, hyper-threaded. Should support 4 ply 
multiprocessing.

%display latex  # LaTeX rendering turned on

Parallelism().set('tensor',4)  #Only works if set to one.
Parallelism().set('linbox',4) 
Parallelism()

M = Manifold(4, 'M')
MChart = M.open_subset('MChart')
Chart.   = MChart.chart(r'u:(-oo,+oo) v:(-oo,+oo) x:(-oo,+oo) 
y:(-oo,+oo)') 

gT= MChart.riemannian_metric('gT')
var('du','dv','dx','dy')

dsds= -du*dv+dx*dx+dy*dy+e^(x*y)*du*du


dsds=dsds.expand()
g00=dsds.coefficient(du,2)
g11=dsds.coefficient(dv,2)
g22=dsds.coefficient(dx,2)
g33=dsds.coefficient(dy,2)
g01=dsds.coefficient(du*dv,1)
g01=g01/2
g10=g01

gT[0,0] = g00.factor() #du du
gT[1,1] = g11.factor() #dv dv
gT[2,2] = g22.factor() #dx dx
gT[3,3] = g33.factor() #dy dy
gT[0,1] = g01.factor() #du dv 
%display latex
show(gT.display())

Metric=gT

Nabla = Metric.connection()

#https://arxiv.org/pdf/gr-qc/0309008.pdf equation 54
%time 
Bach=(Nabla(Metric.cotton()).up(Metric,3)['^u_aub'])+((Metric.schouten().up(Metric))*(Metric.weyl().down(Metric)))['^uv_aubv']
show(Bach.display())
%time 
Bach=Nabla(Nabla(Metric.weyl().down(Metric))).up(Metric,4).up(Metric,5)['^bd_abcd']-(1/2)*((Metric.ricci().up(Metric))*(Metric.weyl().down(Metric)))['^bd_abcd']
show(Bach.display())
%time 
Bach=-(Metric.schouten()*(Metric.weyl().down(Metric))).up(Metric,1).up(Metric,2)['^cd_cdab']
 
- Nabla(Nabla(Metric.schouten())).up(Metric,3)['^c_cab'] + 
Nabla(Nabla(Metric.schouten())).up(Metric,3)['^c_abc']

Cotton=-Nabla(Metric.ricci())['_i[jk]']-1/(2*(4-1))*Nabla(Metric.ricci_scalar()*Metric)['_i[kj]']

%time 
Bach=(Nabla(Cotton).up(Metric,3)['^u_aub'])+((Metric.schouten().up(Metric))*(Metric.weyl().down(Metric)))['^uv_aubv']
show(Bach.display())

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BachTensor.ipynb
Description: Binary data

[sage-support] Re: How do you use SageMath in research, education, ...?

[Matthias Koeppe]

On Saturday, May 23, 2020 at 12:18:08 PM UTC-7, Ingo Dahn wrote:
>
> Sounds like an interesting event, what is the intended audience? 
> Developers? Researchers? Educators?
>

All of the above. We have added some more information at 
https://wiki.sagemath.org/days109
 

> Specific times/tracks for each? 
>

Yes, we will announce a detailed program shortly.
 

> Are there reports from previous events? An Agenda? Will there be records 
> of presentations?
>

Previous SageDays (https://wiki.sagemath.org/Workshops) were in-person 
events. This is the first fully virtual event. We plan to record and make 
available presentations (when the presenters give us permission to do so.)

Matthias

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