memory-hierarchy-2

metrics

No change:

$ go test -bench=. *.go
goos: darwin
goarch: arm64
BenchmarkMetrics/Average_age-8         	    1002	   1180386 ns/op
BenchmarkMetrics/Average_payment-8     	      85	  13663136 ns/op
BenchmarkMetrics/Payment_stddev-8      	      43	  27659781 ns/op
PASS
ok  	command-line-arguments	4.887s

Just fetching a list of ages instead of the whole map (map[UserId]*User -> []int).

BenchmarkMetrics/Average_age-8         	    2397	    500411 ns/op

Converting UserMap into UserData ([]int + []DollarAmount).

BenchmarkMetrics/Average_age-8         	    2391	    500697 ns/op
BenchmarkMetrics/Average_payment-8     	     230	   5311983 ns/op
BenchmarkMetrics/Payment_stddev-8      	     189	   6327712 ns/op

Changing ages to be uint8 instead of int. No difference.

BenchmarkMetrics/Average_age-8         	    2384	    505523 ns/op
BenchmarkMetrics/Average_payment-8     	     234	   5168928 ns/op
BenchmarkMetrics/Payment_stddev-8      	     189	   6325219 ns/op

Do only one division in average age instead of one per element.

BenchmarkMetrics/Average_age-8         	   12769	     94525 ns/op 

Do the same for average (there's still a division by 100 for the cents):

BenchmarkMetrics/Average_payment-8     	    1242	    959322 ns/op
BenchmarkMetrics/Payment_stddev-8      	     528	   2271891 ns/op

Remove divisions by 100 in cents. No change in performance probably because the compiler was already optimizing this.

BenchmarkMetrics/Average_payment-8     	    1242	    964086 ns/op
BenchmarkMetrics/Payment_stddev-8      	     535	   2240803 ns/op

Removing most divisions and optimizing standard deviation. This gets to the provided solution performance (look into solution folder).

BenchmarkMetrics/Average_age-8         	   38312	     31443 ns/op
BenchmarkMetrics/Average_payment-8     	    3556	    342336 ns/op
BenchmarkMetrics/Payment_stddev-8      	     956	   1252118 ns/op

Loop unrolling, barely any difference:

BenchmarkMetrics/Average_age-8         	   38217	     31376 ns/op
BenchmarkMetrics/Average_payment-8     	    3805	    313599 ns/op
BenchmarkMetrics/Payment_stddev-8      	     957	   1254484 ns/op

Multiple accumulators, blazingly fast 🔥 😎 (not by much though at this point).

BenchmarkMetrics/Average_age-8         	   47128	     25440 ns/op
BenchmarkMetrics/Average_payment-8     	    4846	    244435 ns/op
BenchmarkMetrics/Payment_stddev-8      	    2547	    469918 ns/op