This book "Deep Learning and Convolutional Neural Networks for Medical Image Computing" uses an expression "a factor of K-fold".
As we learned about the current state of research on deep learning, I was surprised to find that other investigators had used convolutional neural networks, one type of deep learning, in the past [22, 23]. But there seemed to be something different about the most recent crop of deep learning algorithms. They routinely used GPU processing to accelerate training by as much as a factor of 40-fold. They also used multiple convolution layers and multiple data reduction layers.
It seems that "a factor of 40-fold" means "×40 faster than before".
Is "a factor of K-fold" a idiomatic saying to express this meaning?