Add a constant variable to a cuda.FloatTensor - gpu

Question

I have two question:
1) I'd like to know how can I add/subtract a constante torch.FloatTensor of size 1 to all of the elemets of a torch.FloatTensor of size 30.
2) How can I multiply each element of a torch.FloatTensor of size 30 by a random value (different or not for each).
My code:
import torch
dtype = torch.cuda.FloatTensor
def main():
pop, xmax, xmin = 30, 5, -5
x = (xmax-xmin)*torch.rand(pop).type(dtype)+xmin
y = torch.pow(x, 2)
[miny, indexmin] = y.min(0)
gxbest = x[indexmin]
pxbest = x
pybest = y
v = torch.rand(pop)
vnext = torch.rand()*v + torch.rand()*(pxbest - x) + torch.rand()*(gxbest - x)
main()
What is the best way to do it? I think I should so how convert the gxbest into a torch.FloatTensor of size 30 but how can I do that?
I've try to create a vector:
Variable(torch.from_numpy(np.ones(pop)))*gxbest
But it did not work. The multiplication is not working also.
RuntimeError: inconsistent tensor size
Thank you all for your help!

Answer 1

1) How can I add/subtract a constant torch.FloatTensor of size 1 to all of the elements of a torch.FloatTensor of size 30?
You can do it directly in pytorch 0.2.
import torch
a = torch.randn(30)
b = torch.randn(1)
print(a-b)
In case if you get any error due to size mismatch, you can make a small change as follows.
print(a-b.expand(a.size(0))) # to make both a and b tensor of same shape
2) How can I multiply each element of a torch.FloatTensor of size 30 by a random value (different or not for each)?
In pytorch 0.2, you can do it directly as well.
import torch
a = torch.randn(30)
b = torch.randn(1)
print(a*b)
In case, if you get an error due to size mismatch, do as follows.
print(a*b.expand(a.size(0)))
So, in your case you can simply change the size of gxbest tensor from 1 to 30 as follows.
gxbest = gxbest.expand(30)