  Deep neural networks often suffer from poor generalization caused by complex
and non-convex loss landscapes. One of the popular solutions is Sharpness-Aware
Minimization (SAM), which smooths the loss landscape via minimizing the
maximized change of training loss when adding a perturbation to the weight.
However, we find the indiscriminate perturbation of SAM on all parameters is
suboptimal, which also results in excessive computation, i.e., double the
overhead of common optimizers like Stochastic Gradient Descent (SGD). In this
paper, we propose an efficient and effective training scheme coined as Sparse
SAM (SSAM), which achieves sparse perturbation by a binary mask. To obtain the
sparse mask, we provide two solutions which are based onFisher information and
dynamic sparse training, respectively. In addition, we theoretically prove that
SSAM can converge at the same rate as SAM, i.e., $O(\log T/\sqrt{T})$. Sparse
SAM not only has the potential for training acceleration but also smooths the
loss landscape effectively. Extensive experimental results on CIFAR10,
CIFAR100, and ImageNet-1K confirm the superior efficiency of our method to SAM,
and the performance is preserved or even better with a perturbation of merely
50% sparsity. Code is availiable at
https://github.com/Mi-Peng/Sparse-Sharpness-Aware-Minimization.
