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The "Python Machine Learning (1st edition)" book code repository and info resource
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ValueError: operands could not be broadcast together with shapes (200,) (30000,) #84

Closed donet3088 closed 4 years ago

donet3088 commented 4 years ago

I am working on a finite element code in python. It is originally for the diffusion equation but I want to modify it for the wave equation and include a ricker source term. I tried adding the source term and it produces an error. Below is the code and error

from IPython import display from matplotlib.tri import Triangulation, LinearTriInterpolator

deltat = 0.001 numIterations = 30 mass = numpy.zeros((NPOINTS,NPOINTS)) stiffness = numpy.zeros((NPOINTS,NPOINTS)) phi = numpy.zeros((NPOINTS,)) phi_old = numpy.zeros((NPOINTS,))

f0= 5 # Center frequency Ricker-wavelet q0= 100 # Maximum amplitude Ricker-Wavelet t=np.arange(0,numIterations,deltat) # Time vector

tau=np.pif0(t-1.5/f0) q=q0(1.0-2.0tau*2.0)np.exp(-tau**2)

xi = np.linspace(0, L, 200) yi = np.linspace(0, H, 200) Xi, Yi = np.meshgrid(xi, yi)

updateMatrix(mass,stiffness,phi) mat = mass/deltat + stiffness triang = Triangulation(points[:,0], points[:,1])

for iteration in range(1,numIterations+1): phi_old = phi

rhs = numpy.dot(mass/deltat, phi_old)
rhs = rhs + q
phi = numpy.linalg.solve(mat,rhs)

interpolator = LinearTriInterpolator(triang, phi) zi = interpolator(Xi, Yi) fig1 = pylab.figure(1) pylab.imshow(zi)

fig2 = pylab.figure(2) xanal, yanal = analytical(numIterations*deltat) pylab.plot(xanal,yanal,"-") pylab.plot(Xi[100,:],zi[100,:]) fig2.savefig("comparison.png",format="PNG")

ValueError Traceback (most recent call last)

in 29 30 rhs = numpy.dot(mass/deltat, phi_old) ---> 31 rhs = rhs + q 32 phi = numpy.linalg.solve(mat,rhs) 33 interpolator = LinearTriInterpolator(triang, phi) ValueError: operands could not be broadcast together with shapes (200,) (30000,)
rasbt commented 4 years ago

The error message means that rhs is a 200-element vector, and q is a 30000-element vector. The problem is that the vectors should have the same size in order to add them via rhs = rhs + q.

I suggest checking (e.g. printing) the values of some of the variables computed earlier to track down where the dimension issue occurs so that you can fix it.