I am facing the same issue with the FastAI v2 library. I am trying to work on Kaggle’s QuickDraw dataset. The data comes in the form of a CSV file like below:
The “drawing” column represents the drawing data points from which we can construct an image while the “word” column represents the label. Now of course, I can first create and save the images into folder and then train a Fastai model in the general imagenet way, or I could generate the images on the fly.
The drawback of the first method is, It will take forever to save the images to disk, not to mention the storage space. The better way is to generate it the images on the fly.
So I wrote the following Datablock to be able to do it.
# Function to generate image from strokes
def draw_to_img(strokes, im_size = 256):
fig, ax = plt.subplots()
for x, y in strokes:
ax.plot(x, -np.array(y), lw = 10)
ax.axis('off')
fig.canvas.draw()
A = np.array(fig.canvas.renderer._renderer) # converting them into array
plt.close('all')
plt.clf()
A = (cv2.resize(A, (im_size, im_size)) / 255.) # image resizing to uniform format
return A[:, :, :3]
class ImageDrawing(PILBase):
@classmethod
def create(cls, fns):
strokes = json.loads(fns)
img = draw_to_img(strokes, im_size=256)
img = PILImage.create((img * 255).astype(np.uint8))
return img
def show(self, ctx=None, **kwargs):
t1 = self
if not isinstance(t1, Tensor): return ctx
return show_image(t1, ctx=ctx, **kwargs)
def ImageDrawingBlock():
return TransformBlock(type_tfms=ImageDrawing.create, batch_tfms=IntToFloatTensor)
And here is the full datablock:
QuickDraw = DataBlock(
blocks=(ImageDrawingBlock, CategoryBlock),
get_x=lambda x:x[1],
get_y=lambda x:x[5].replace(' ','_'),
splitter=RandomSplitter(valid_pct=0.005),
item_tfms=Resize(128),
batch_tfms=aug_transforms()
)
data = QuickDraw.dataloaders(df, bs=16, path=path)
With this, I am able to effectively create the images on the fly and train the model. But the problem is, mid training, Just like the original author of the question, I have the same problem with my 64 GB RAM eventually being completly used up. 
Its exactly as the author has described.
I tried the solution which seemingly worked for the author, but it doesnt work for me. Im using the V2 Library and by this point I have spent quite some time trying to fix this, would really appreciate any help!
Thanks in advance. @sgugger @StatisticDean
P.S. The 'Docs" and “Tutorial” links in this github discussion https://github.com/fastai/fastai/issues/2068 gives a 404 not found error.
