CPU: Difference between revisions

Revision as of 21:56, 19 December 2018

Pico-8 keeps track of CPU usage using two values: a Lua instruction usage, and a system usage.

The function stat(1) returns the total (Lua + system) usage for the current frame, and stat(2) returns the system usage.

Only a few functions have a system usage, measured in ticks. There are 4194304 ticks in a second (2^22), so about 69905 ticks per frame at 60 FPS.

Function	Ticks	Notes
`cls`	`1024`	same cost as `rectfill` of same size
`print`	`2+n*8`	`n` is the number of characters in the string spaces and newlines count as one character double-width glyphs count as one character offscreen characters count
`spr`
`sspr`
`rect`
`rectfill`	`max(1,flr(n/16))`	`n` is the number of pixels drawn (width × height)
`circ`
`circfill`
`line`	`ceil(n/2)`	`n` is the number of pixels drawn; there is an additional cost of `1` if at least one pixel had to be clipped
`map` / `mapdraw`
`music`	`16`	no cost if no argument
`sfx`	`16`	no cost if no argument
`memcpy`	`n+1`	`n` is the number of bytes copied
`memset`	`max(1,ceil(n/2))`	`n` is the number of bytes set
`reload`	`max(1,n*8)`	`n` is the number of bytes reloaded
`btn`	`4`	no cost if no argument
`btnp`	`4`	no cost if no argument
`rnd`	`4`
`sqrt`	`24`	only `16` if argument is zero
`stat`	`16`

@@ Line 12: / Line 12: @@
 | [[cls|<code>cls</code>]] || <code>1024</code> || same cost as [[rectfill|<code>rectfill</code>]] of same size
 |-
-| [[print|<code>print</code>]] || ||
+| [[print|<code>print</code>]] || <code>2+n*8</code>
+||<code>n</code> is the number of characters in the string
+spaces and newlines count as one character
+double-width glyphs count as one character
+offscreen characters count
 |-
 | [[spr|<code>spr</code>]] || ||
@@ Line 34: / Line 41: @@
 | [[sfx|<code>sfx</code>]] || <code>16</code> || no cost if no argument
 |-
-| [[memcpy|<code>memcpy</code>]] || ||
+| [[memcpy|<code>memcpy</code>]] || <code>n+1</code>
+||<code>n</code> is the number of bytes copied
 |-
-| [[memset|<code>memset</code>]] || ||
+| [[memset|<code>memset</code>]] || <code>max(1,ceil(n/2))</code>
+||<code>n</code> is the number of bytes set
 |-
-| [[reload|<code>reload</code>]] || ||
+| [[reload|<code>reload</code>]] || <code>max(1,n*8)</code>
+||<code>n</code> is the number of bytes reloaded
 |-
 | [[btn|<code>btn</code>]] || <code>4</code> || no cost if no argument