Cartesian Product in Go
I am still fairly new to go, and would appreciate any tips on style, best practices, etc, but am especially interested to know if this non-recursive cartesian product implementation can be made significantly faster (eg, when the number of results in the result set is on the order of 1e9).
I've played around with adding more goroutines, but parallelism doesn't seem to help much, if at all. I may be missing a much better approach though.
https://play.golang.org/p/H-M6CbmeFoV
package main
import (
"fmt"
)
// Given a mixed base, returns a function that:
//
// Increments a number, represented as a slice of digits, defined
// in that base. For example, if our base is 2 3 2, we'll count
// like this:
//
// 0 0 0 ; 0 0 1; 0 1 0; 0 1 1; 0 2 0; 0 2 1;
// 1 0 0 ; 1 0 1; 1 1 0; 1 1 1; 1 2 0; 1 2 1;
func mixedBaseInc(bases int) func(*int) {
return func(digits *int) {
ret := *digits
i := len(ret) - 1
for {
base := bases[i]
ret[i] = (ret[i] + 1) % base
noCarry := ret[i] != 0
if noCarry || i == 0 {
return
}
i--
}
}
}
func pick(indexes int, params interface{}) interface{} {
ret := make(interface{}, len(params))
for i, x := range indexes {
ret[i] = params[i][x]
}
return ret
}
func XProd(params ...interface{}) chan interface{} {
var paramLens, digits int
numElms := 1
c := make(chan interface{})
for _, x := range params {
paramLens = append(paramLens, len(x))
numElms *= len(x)
digits = append(digits, 0)
}
inc := mixedBaseInc(paramLens)
go func() {
defer close(c)
for i := 0; i < numElms; i++ {
c <- pick(digits, params)
inc(&digits)
}
}()
return c
}
func main() {
for x := range XProd(interface{}{1, 2, 3}, interface{}{4, 5}) {
fmt.Println(x)
}
}
go
asked 3 mins ago
Jonah
3,411617
add a comment |
I am still fairly new to go, and would appreciate any tips on style, best practices, etc, but am especially interested to know if this non-recursive cartesian product implementation can be made significantly faster (eg, when the number of results in the result set is on the order of 1e9).
I've played around with adding more goroutines, but parallelism doesn't seem to help much, if at all. I may be missing a much better approach though.
https://play.golang.org/p/H-M6CbmeFoV
package main
import (
"fmt"
)
// Given a mixed base, returns a function that:
//
// Increments a number, represented as a slice of digits, defined
// in that base. For example, if our base is 2 3 2, we'll count
// like this:
//
// 0 0 0 ; 0 0 1; 0 1 0; 0 1 1; 0 2 0; 0 2 1;
// 1 0 0 ; 1 0 1; 1 1 0; 1 1 1; 1 2 0; 1 2 1;
func mixedBaseInc(bases int) func(*int) {
return func(digits *int) {
ret := *digits
i := len(ret) - 1
for {
base := bases[i]
ret[i] = (ret[i] + 1) % base
noCarry := ret[i] != 0
if noCarry || i == 0 {
return
}
i--
}
}
}
func pick(indexes int, params interface{}) interface{} {
ret := make(interface{}, len(params))
for i, x := range indexes {
ret[i] = params[i][x]
}
return ret
}
func XProd(params ...interface{}) chan interface{} {
var paramLens, digits int
numElms := 1
c := make(chan interface{})
for _, x := range params {
paramLens = append(paramLens, len(x))
numElms *= len(x)
digits = append(digits, 0)
}
inc := mixedBaseInc(paramLens)
go func() {
defer close(c)
for i := 0; i < numElms; i++ {
c <- pick(digits, params)
inc(&digits)
}
}()
return c
}
func main() {
for x := range XProd(interface{}{1, 2, 3}, interface{}{4, 5}) {
fmt.Println(x)
}
}
go
asked 3 mins ago
Jonah
3,411617
add a comment |
I am still fairly new to go, and would appreciate any tips on style, best practices, etc, but am especially interested to know if this non-recursive cartesian product implementation can be made significantly faster (eg, when the number of results in the result set is on the order of 1e9).
I've played around with adding more goroutines, but parallelism doesn't seem to help much, if at all. I may be missing a much better approach though.
https://play.golang.org/p/H-M6CbmeFoV
package main
import (
"fmt"
)
// Given a mixed base, returns a function that:
//
// Increments a number, represented as a slice of digits, defined
// in that base. For example, if our base is 2 3 2, we'll count
// like this:
//
// 0 0 0 ; 0 0 1; 0 1 0; 0 1 1; 0 2 0; 0 2 1;
// 1 0 0 ; 1 0 1; 1 1 0; 1 1 1; 1 2 0; 1 2 1;
func mixedBaseInc(bases int) func(*int) {
return func(digits *int) {
ret := *digits
i := len(ret) - 1
for {
base := bases[i]
ret[i] = (ret[i] + 1) % base
noCarry := ret[i] != 0
if noCarry || i == 0 {
return
}
i--
}
}
}
func pick(indexes int, params interface{}) interface{} {
ret := make(interface{}, len(params))
for i, x := range indexes {
ret[i] = params[i][x]
}
return ret
}
func XProd(params ...interface{}) chan interface{} {
var paramLens, digits int
numElms := 1
c := make(chan interface{})
for _, x := range params {
paramLens = append(paramLens, len(x))
numElms *= len(x)
digits = append(digits, 0)
}
inc := mixedBaseInc(paramLens)
go func() {
defer close(c)
for i := 0; i < numElms; i++ {
c <- pick(digits, params)
inc(&digits)
}
}()
return c
}
func main() {
for x := range XProd(interface{}{1, 2, 3}, interface{}{4, 5}) {
fmt.Println(x)
}
}
go
asked 3 mins ago
Jonah
3,411617
I am still fairly new to go, and would appreciate any tips on style, best practices, etc, but am especially interested to know if this non-recursive cartesian product implementation can be made significantly faster (eg, when the number of results in the result set is on the order of 1e9).
I've played around with adding more goroutines, but parallelism doesn't seem to help much, if at all. I may be missing a much better approach though.
https://play.golang.org/p/H-M6CbmeFoV
package main
import (
"fmt"
)
// Given a mixed base, returns a function that:
//
// Increments a number, represented as a slice of digits, defined
// in that base. For example, if our base is 2 3 2, we'll count
// like this:
//
// 0 0 0 ; 0 0 1; 0 1 0; 0 1 1; 0 2 0; 0 2 1;
// 1 0 0 ; 1 0 1; 1 1 0; 1 1 1; 1 2 0; 1 2 1;
func mixedBaseInc(bases int) func(*int) {
return func(digits *int) {
ret := *digits
i := len(ret) - 1
for {
base := bases[i]
ret[i] = (ret[i] + 1) % base
noCarry := ret[i] != 0
if noCarry || i == 0 {
return
}
i--
}
}
}
func pick(indexes int, params interface{}) interface{} {
ret := make(interface{}, len(params))
for i, x := range indexes {
ret[i] = params[i][x]
}
return ret
}
func XProd(params ...interface{}) chan interface{} {
var paramLens, digits int
numElms := 1
c := make(chan interface{})
for _, x := range params {
paramLens = append(paramLens, len(x))
numElms *= len(x)
digits = append(digits, 0)
}
inc := mixedBaseInc(paramLens)
go func() {
defer close(c)
for i := 0; i < numElms; i++ {
c <- pick(digits, params)
inc(&digits)
}
}()
return c
}
func main() {
for x := range XProd(interface{}{1, 2, 3}, interface{}{4, 5}) {
fmt.Println(x)
}
}
go
go
asked 3 mins ago
Jonah
3,411617
asked 3 mins ago
Jonah
3,411617
asked 3 mins ago
Jonah
3,411617
asked 3 mins ago
Jonah
3,411617
asked 3 mins ago
Jonah
3,411617
3,411617
add a comment |
add a comment |
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