# SnippetGetNearestUnit

#### Dirac

##### 22710180
The fastest, easiest and with more flexible way to retrieve the nearest unit from a point

JASS:
``````library GetNearestUnit /* v1.1.1

*/uses/*

***********************************************************************
*
*   function GetNearestUnit takes real x, real y, boolexpr filter returns unit
*   function GetFarthestUnit takes real x, real y, boolexpr filter returns unit
*
*   function GetNearestUnitEx takes real x, real y, real range, boolexpr filter, integer i returns unit
*   function GetFarthestUnitEx takes real x, real y, real range, boolexpr filter, integer i returns unit
*       -   The extra integer argument skips that many units in the
*       -   list of near units.
*       -   Ex: If takes &quot;2&quot; then it would return the second nearest
*       -   unit.
*
***********************************************************************
*
*   HOW TO USE:
*
*   function SomeFilter takes nothing returns boolean
*       return GetUnitTypeId(GetFilterUnit())==&#039;hfoo&#039;
*   endfunction
*
*   call GetNearestUnit(0,0,Filter(function SomeFilter)
*
*   -   In the example above the script would only pick the closest
*   -   footman from the point 0,0
*
**********************************************************************/

globals
//*********************************************************************
//  Default circumference pick range for non extended functions.
private constant real DEFAULT_RANGE = 2000
endglobals

private struct List extends array

unit unit
real distance

//! runtextmacro MERGE_SORT(&quot;sort&quot;,&quot;v1.distance&gt;v2.distance&quot;)

static method for takes real x, real y, real r, boolexpr c returns nothing
local List node
local unit e
call GroupEnumUnitsInRange(bj_lastCreatedGroup,x,y,r,c)
loop
set e = FirstOfGroup(bj_lastCreatedGroup)
exitwhen e==null
set node = List.allocate()
set node.unit = e
set node.distance = (GetUnitX(e)-x)*(GetUnitX(e)-x)+(GetUnitY(e)-y)*(GetUnitY(e)-y)
call base.insertNode(node)
call GroupRemoveUnit(bj_lastCreatedGroup,e)
endloop
call sort(base)
set e = null
endmethod

endstruct

function GetNearestUnitEx takes real x, real y, real r, boolexpr c, integer i returns unit
local List this = List.base
call List.for(x,y,r,c)
loop
set this = this.next
set i = i-1
endloop
call List.base.clearNode()
return this.unit
endfunction

function GetFarthestUnitEx takes real x, real y, real r, boolexpr c, integer i returns unit
local List this = List.base
call List.for(x,y,r,c)
loop
set this = this.prev
set i = i-1
endloop
call List.base.clearNode()
return this.unit
endfunction

function GetNearestUnit takes real x, real y, boolexpr c returns unit
return GetNearestUnitEx(x,y,DEFAULT_RANGE,c,1)
endfunction

function GetFarthestUnit takes real x, real y, boolexpr c returns unit
return GetFarthestUnitEx(x,y,DEFAULT_RANGE,c,1)
endfunction

endlibrary``````

JASS:
``````library GetNearestUnit /* v1.1.0

*/uses/*

***********************************************************************
*
*   function GetNearestUnit takes real x, real y, boolexpr filter returns unit
*   function GetFarthestUnit takes real x, real y, boolexpr filter returns unit
*
*   function GetNearestUnitEx takes real x, real y, real r, boolexpr filter, integer i returns unit
*   function GetFarthestUnitEx takes real x, real y, real r, boolexpr filter, integer i returns unit
*       -   The extra integer argument skips that many units in the
*       -   list of near units.
*       -   Ex: If takes &quot;2&quot; then it would return the second nearest
*       -   unit.
*       -   The extra real argument is the range to pick unit
*       -   return null if no unit is picked.
***********************************************************************
*
*   HOW TO USE:
*
*   function SomeFilter takes nothing returns boolean
*       return GetUnitTypeId(GetFilterUnit())==&#039;hfoo&#039;
*   endfunction
*
*   call GetNearestUnit(0,0,Filter(function SomeFilter)
*
*   -   In the example above the script would only pick the closest
*   -   footman from the point 0,0
*
**********************************************************************/

globals
//*********************************************************************
//  Will not be used on Ex&#039;s functions
private constant real DEFAULT_RANGE = 99999.
endglobals

private struct List extends array

unit unit
real distance

//! runtextmacro MERGE_SORT(&quot;sort&quot;,&quot;v1.distance&gt;v2.distance&quot;)

static method for takes real x, real y, real r, boolexpr c returns thistype
local List this = List.createNode()
local List node
local unit e
call GroupEnumUnitsInRange(bj_lastCreatedGroup,x,y,r,c)
loop
set e = FirstOfGroup(bj_lastCreatedGroup)
exitwhen e==null
set node = List.allocate()
set node.unit = e
set node.distance = (GetUnitX(e)-x)*(GetUnitX(e)-x)+(GetUnitY(e)-y)*(GetUnitY(e)-y)
call this.insertNode(node)
call GroupRemoveUnit(bj_lastCreatedGroup,e)
endloop
call sort(this)
return this
endmethod

endstruct

function GetNearestUnitEx takes real x, real y, real r, boolexpr c, integer i returns unit
local List this = List.for(x,y,r,c)
local unit e
loop
set this = this.next
set i = i-1
endloop
set e = this.unit
call this.flushNode()
return e
endfunction

function GetFarthestUnitEx takes real x, real y, real r, boolexpr c, integer i returns unit
local List this = List.for(x,y,r,c)
local unit e
loop
set this = this.prev
set i = i-1
endloop
set e = this.unit
call this.flushNode()
return e
endfunction

function GetNearestUnit takes real x, real y, boolexpr c returns unit
local List this = List.for(x,y,DEFAULT_RANGE,c)
local unit e = this.next.unit
call this.flushNode()
return e
endfunction

function GetFarthestUnit takes real x, real y, boolexpr c returns unit
local List this = List.for(x,y,DEFAULT_RANGE,c)
local unit e = this.prev.unit
call this.flushNode()
return e
endfunction

endlibrary``````

Added the range argument to the extended functions.

Why would that be any faster than a function that inlines: the grouping, then iterates over every unit and calculates the distance and thus finds the closes/farthest unit? Function calls take time, and ones with arguments take even more time =), if speed is what you're aming for.

Why not just:
JASS:
``````globals
private constant real MAX_DIST_POW = 99999999
endglobals

function GetNearestUnit takes real x, real y,real r, boolexpr c returns unit
local unit u
local unit e
local real du=MAX_DIST_POW
local real de
call GroupEnumUnitsInRange(bj_lastCreatedGroup,x,y,r,c)
loop
set e=FirstOfGroup(bj_lastCreatedGroup)
exitwhen e==null
set de=(GetUnitX(e)-x)*(GetUnitX(e)-x)+(GetUnitY(e)-y)*(GetUnitY(e)-y)
if de&lt;du then
set u=e
set du=d
endif
call GroupRemoveUnit(bj_lastCreatedGroup,e)
endloop
return u
endfunction``````

there should be another way to find the closest unit.
You don't save anything from "speed" of code.
GroupEnumUnitsInRange(bj_lastCreatedGroup,x,y,r,c) forces to get units from a certain area, which searches for all units and then puts them into a group and then you search for every unit of them to find the closest.

An A.I.D.S. like group enumeration and then a search through every single unit is faster. You save an extra search.

Although there is a graphs node solution with Dijkstra algorithm but I don't know if it's faster.

there should be another way to find the closest unit.
You don't save anything from "speed" of code.
GroupEnumUnitsInRange(bj_lastCreatedGroup,x,y,r,c) forces to get units from a certain area, which searches for all units and then puts them into a group and then you search for every unit of them to find the closest.

An A.I.D.S. like group enumeration and then a search through every single unit is faster. You save an extra search.

Although there is a graphs node solution with Dijkstra algorithm but I don't know if it's faster.
I already conducted this using Nestharus's Unit List and it's by far slower.
The native is the best way to pick units.

>I already conducted this using Nestharus's Unit List and it's by far slower.
The native is the best way to pick units.

I agree.

> which searches for all units and then puts them into a group
How do you know that? You've seen the code?

Even if that's the case it is still native code (C++ probably) vs interpreted (Jass2 probably) =).

Yes i've seen it, but you may be right. the coding is in C, which is really faster than jass2.
The native takes all units in game and checks their range, if it's the range you've put or lower the unit goes in group. The first unit must be the closest one i think, check it.

Why not just:
JASS:
``````globals
private constant real MAX_DIST_POW = 99999999
endglobals

function GetNearestUnit takes real x, real y,real r, boolexpr c returns unit
local unit u
local unit e
local real du=MAX_DIST_POW
local real de
call GroupEnumUnitsInRange(bj_lastCreatedGroup,x,y,r,c)
loop
set e=FirstOfGroup(bj_lastCreatedGroup)
exitwhen e==null
set de=(GetUnitX(e)-x)*(GetUnitX(e)-x)+(GetUnitY(e)-y)*(GetUnitY(e)-y)
if de&lt;du then
set u=e
set du=d
endif
call GroupRemoveUnit(bj_lastCreatedGroup,e)
endloop
return u
endfunction``````

?

@muzik
Yes this is basically the fastest way to do it (That I know of), although you are forgetting to null the e variable so it actually leaks [not a big deal though =)]

Well, actually the fastest way to do it, that I know of would be this:

JASS:
``````globals
group G0 = CreateGroup()
unit  U0 = null
unit  U1 = null
real  R0
real  R1
real  R2
real  R3
endglobals

//! textmacro CLOSEST_UNIT takes x, y, range, filter, returns_unit
set R0 = 9999999
call GroupEnumUnitsInRange(G0, \$x\$, \$y\$, \$range\$, \$filter\$)

loop
set U0 = FirstOfGroup(G0)
exitwhen U1 == null

set R1 = \$x\$ - GetUnitX(U0)
set R2 = \$y\$ - GetUnitY(U0)
set R3 = R1 * R1 + R2 * R2

if R0 &gt; R3 then
set R0 = R3
set U1 = U0
endif

call GroupRemoveUnit(G0, U0)
endloop

set \$returns_unit\$ = U1
//! endtextmacro``````

I.e to inline even the call to the function =):

An example use might be:
JASS:
``````local unit u
//! runtextmacro CLOSEST_UNIT(&quot;GetUnitX(Hero[0]), &quot;GetUnitY(Hero[0]&quot;, &quot;RANGE&quot;, &quot;null&quot;, &quot;u&quot;)
call KillUnit(u) // actually kills Hero[0] because the filter is null =)``````

@muzik
Yes this is basically the fastest way to do it (That I know of), although you are forgetting to null the e variable so it actually leaks [not a big deal though =)]

"u" leaks as well That's why using a global variable to return the nearest unit is better.

Oh yeah, I forgot about "u" leak, using a global may solve it.
Not necesary null "e", because loop condition is exitwhen e==null, so e is null when loop ends.

@muzk

Yeah, you are actually right.

I just went all full retard when i realize there was no need for that local, or a globals to replace it. The List.unit array's value isn't lost when the list is flushed, mild brain blackout I had there.

Update v1.1.1
-Improved Code efficiency

I'm sticking with mergesort because I really would like to be able to know the 2nd, 3rd or any unit in the list.
The speed difference is so minimal it's not even worth the debate

>I'm sticking with mergesort because I really would like to be able to know the 2nd, 3rd or any unit in the list.

If you don't mind can you give me an example where based on the distance the 2nd, 3rd, etc. unit is actually needed?

>The speed difference is so minimal it's not even worth the debate
=) Well... I did a little benchmark 1000 calls for all and the results were (same arguments were passed for all cases of course):

Dirac's: time = 0.872
muzk's: time = 0.178
inlined: time = 0.134 (inlined using textmacro and only two calls to the GetUnitX/Y natives)

So no offense but yours is actually 5 to 6 times slower, but you are probably right it's not worth the debate =).

If you don't mind can you give me an example where based on the distance the 2nd, 3rd, etc. unit is actually needed?
Use your imagination, maybe an ability that deals decaying AoE damage to nearby units, starting by 300 to the closest, 270 for the second, 240 for the third and so on.

An instant casted Chain Lightning which jumps thorugh each unit, from the closest to the farthest.

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