Multithreaded Data Augmentations

Megh_Bhalerao: <p>Hi,<br>
Is there a way to implement Multi threaded data augmentation in pytorch? I am not very familiar with the multi-threading concept but I have a basic understanding of multithreading. My current augmentations are consuming too much time (my augmentations happen on CPU as numpy arrays) and then the torch tensor gets copied to the GPU for forward and backward passes. Any way to speedup the data augmentations? Any suggestions would be of great help. My dataloader looks something like :</p>
<pre><code class="lang-auto">from augmentations.color_aug import *
from augmentations.noise_aug import *
from augmentations.spatial_augs import *
from augmentations.utils import *
import nibabel as nib
import torch
from torch.utils.data.dataset import Dataset
import numpy as np
import pandas as pd
from torch.utils.data import DataLoader
import os
import random
from all_augmentations import *
from utils import *
import random
class TumorSegmentationDataset(Dataset):
    def __init__(self, csv_file, which_gt):
        self.df = pd.read_csv(csv_file)
        self.which_gt = which_gt
    def __len__(self):
        return len(self.df)

    def transform(self,img ,gt):
        img, gt = augment_spatial_2(img, gt, (128,128,128))
        img, gt = img.copy(), gt.copy()
        img, gt = img[0], gt[0]        
        if random.random()&lt;0.12:
            img, gt = augment_rot90(img, gt)
            img, gt = img.copy(), gt.copy()        
        if random.random()&lt;0.12:
            img, gt = augment_mirroring(img, gt)
            img, gt = img.copy(), gt.copy()
        if random.random()&lt;0.12:
            img, gt = augment_rotate_angle(img, gt, 45)
            img, gt = img.copy(), gt.copy() 
        if random.random()&lt;0.12:
            img, gt = augment_rotate_angle(img, gt, 180)
            img, gt = img.copy(), gt.copy() 
        if random.random() &lt; 0.12:
            img, gt = np.fliplr(img).copy(), np.fliplr(gt).copy()
        if random.random() &lt; 0.12:
            img[1] = gaussian(img[1],True,0,0.1)   
            img[2] = gaussian(img[2],True,0,0.1)
            img[3] = gaussian(img[3],True,0,0.1)
            img[0] = gaussian(img[0],True,0,0.1)
          
        return img,gt
        
    def rcrop(self,imshape,psize):        
        xshift = random.randint(0,imshape[0]-psize)
        yshift = random.randint(0,imshape[1]-psize)
        zshift = random.randint(0,imshape[2]-psize)
        return xshift, yshift, zshift

    def __getitem__(self, index):
        t1_path = self.df.iloc[index, 0]
        t2_path = self.df.iloc[index,2]
        t1ce_path = self.df.iloc[index,3]
        flair_path = self.df.iloc[index,5]
        gt_which = self.which_gt
        gt_path = self.df.iloc[index,7]
        gt = nib.load(gt_path).get_fdata()
        t1 = nib.load(t1_path).get_fdata()
        t2 = nib.load(t2_path).get_fdata()
        t1ce = nib.load(t1ce_path).get_fdata()
        flair = nib.load(flair_path).get_fdata()

        t1 = np.expand_dims(t1,axis = 0)
        t2 = np.expand_dims(t2,axis = 0)
        t1ce = np.expand_dims(t1ce,axis = 0)
        flair = np.expand_dims(flair,axis = 0)
        image = np.concatenate((t1,t2,t1ce,flair),axis = 0)        

        if gt_which == 0:
            gt = one_hot_nonoverlap(gt)
        if gt_which == 1:
            gt = one_hot_2_overlap(gt)
        image = np.expand_dims(image, axis = 0)
        gt = np.expand_dims(gt, axis = 0)


        image, gt = self.transform(image, gt)
        
        sample = {'image': image, 'gt' : gt}
        return sample
'''
Any way to speedup the dataloader? It's taking a major share of the training time.
Thanks in advance for any suggestions</code></pre>