marv's profile - activity

i can reproduce this. If it helps you for the moment ngon=polytopes.regular_polygon(122).dilation(181/10) works.

And now it doesn't work any more?? :/. It was ok for about 2 days. I'm confused, sage planted some symbolic links in my dropbox folder

I can't tell you where this error comes from, but i also got it when setting up syncing with Dropbox lately.

As was mentioned in this question Dropbox has a problem with symbolic links.

So I have come to a working solution for me by just symlinking the actual folder of my notebook files, which is /home/myname/.sage/sage_notebook.sagenb/home/admin in my case to a Dropbox folder

ln -s /home/myname/Dropbox/sage/admin/ /home/myname/.sage/sage_notebook.sagenb/home/admin

this done also on my laptop works very good for me. Don't forget to put the files from admin, which is also symlink in first place, into your Dropbox folder.

I have no idea about symlinks in mac os and I can't garantee for anything though.. Greetings, marv

you're right, the problem doesn't occur when defining all decimals as fractions

thanks for making a track ticket

Hi sage community

My question again arises from exercises in technical chemistry done in sage. I wanted to calculate an definite integral (number of transfer units).

var('x')
ys=0.06+2*(x-0.0275)
xs=ys/1.516

#my function
i=1/(xs/(1+xs)-x/(1+x))
#print i
#show(plot(i,x,0,0.03))

#I, the indefinite integral of i
I=integral(i,x)
#print I
#show(plot(I,x,0,0.03))

#three methods too calculate the integral
print n(I(x=0.0275)-I(x=0))
print numerical_integral(i,0,0.0275)
print integral(i,x,0,0.275)

The first two methods work fine. The last method gives me the infinite of the following messages.

;;;
;;; Detected access to protected memory, also kwown as 'bus or segmentation fault'.
;;; Jumping to the outermost toplevel prompt
;;;

This is a bug, isn't it? However, i have no idea how integrate() works.

Greetings, marv

Ok, I think i figured it out. The problem is, that i filled many lists with exact expressions and i exeeded the memmory available. Take the following lines from the loop:

c123.append(c123[i] - k1*step - k2*step)

After changing them all to something like:

c123.append(n(c123[i] - k1*step - k2*step))

everything works fine.

Thanks for tmonteil for your offering. If you want you can still take the code and have a look at your system memory. Maybe it would be good, if sage cloud tells if too much memory is used.

k1=2*10^(-4)
k1s=2*10^(-4)
k2=10^(-4)
k2s=10^(-4)
k3=5*10^(-5)
k4=10^(-4)
k5=5*10^(-5)

c123 = [2.5]
c13 = [0]
c1 = [0]
c12 = [0]
c2 = [0]
tList = [0]

#stepsize in seconds
step = 100
maxFound = False

for i in range(200):
    #beginnt mit 0 beechnungen fü nächsten zeitschitt
    t=step*i
    tList.append(t)

    #zwei geschwindigkeitsgesetze, beechnung fü n+1
    if c123[i] > 0.5 :
        c123.append(c123[i] - k1*step - k2*step)
        c13.append(c13[i] + k1*step - k3*step*c13[i])
        c12.append(c12[i] + k2*step - k4*step*c12[i] - k5*step*c12[i]^2)
    else:
        c123.append(c123[i] - k1s*step*c123[i] - k2*step*c123[i])
        c13.append(c13[i] + k1s*step*c123[i] - k3*step*c13[i])
        c12.append(c12[i] + k2s*step*c123[i] - k4*step*c12[i] - k5*step*c12[i]^2)
    #unabhängig von dem zeitpunkt
    c1.append(c1[i] + k3*step*c13[i] + k4*step*c12[i])
    c2.append(c2[i] + k5*step*c12[i]^2 )

    if (c13[i+1]<c13[i]) and (not maxFound):
        print "Maximum found for c13 found at", t, "s, bzw. ", n(t/3600), "h"
        print "Umsatz:", (c123[0]-c123[i])/c123[0]
        print "Selektivität 13:", (c13[i]-c13[0])/(c123[0]-c123[i])
        ausbeute13 = (c13[i]-c13[0])/c123[0]
        print "Ausbeute 13:", ausbeute13
        print "Selektivität 12:", (c12[i]-c12[0])/(c123[0]-c123[i])
        print "Selektivität 1:", (c1[i]-c1[0])/(c123[0]-c123[i])
        print "Selektivität 2:", (c2[i]-c2[0])/(c123[0]-c123[i])
        maxFound = True
    #pint t, "s"
    #pint c123[i], n(c13[i]), n(c1[i])
plotObject = list_plot(zip(tList,c123),plotjoined=True)
plotObject += list_plot(zip(tList,c13),plotjoined=True,color='red')
plotObject += list_plot(zip(tList,c12),plotjoined=True,color='green')
plotObject += list_plot(zip(tList,c1),plotjoined=True,color='orange')
plotObject += list_plot(zip(tList,c2),plotjoined=True,color='yellow')
plotObject.show()

Hi everybody

I'm working on an exercise in technical chemistry and try to find concentration progresses by numerical calculation. Note that im pretty new to Sage and Python.

The problem i encounter is that as soon as i want to use more than 20 iterations, Sage cloud doesn't finish. I was able to have more iterations when my loop was smaller.

Is there a limitation on the computional power, that is provided by Sage cloud? If you think the problem is with my code, I will post it.

Greetings, marv