Student Question

In a Parameter $-$ Server $($PS$)$ based Asynchronous SGD training system, there are two learners. Assume a learner sends gradients to the PS$.$ PS updates weights and a learner pulls the weights from the PS in zero amount of time $($i$.$ e$.$ after the learner sends gradients to the PS$.$ it can receive updated weights from PS immediately$).$ Now assume learner $1$ runs at about $2\mathrm{.}5x$ the speed of learner $2.$ Learner I calculates gradients g$[$L$.,$ I$]$ at second $1.$ g$[$U$.,2]$ at second $2.$ g$[$LI$.3]$ at second $3.$ g$[$U$.1]$ at second $1.$ Learner $2$ calculates gradients g$[$L$2,1]$ at second $2\mathrm{.}5.$ g$[$L$2,2]$ at second $5.$ Updates to weights are instant once a gradient is available. Calculate the staleness inumber of weight updates between reading and updating $2.1).$ means $i-$th learner's $j-$th calculated gradients$).$