Salis is an artificial life simulation, based on Tom Ray's Tierra system. On it, virtual organisms compete for space and time. Over time, organisms evolve and replicate.
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SALIS: A-Life Simulator

SALIS running simulation


SALIS is my newest artificial life project. Mainly a re-take on Tom Ray's TIERRA simulation, but with my very own set of tweaks. Having a grasp on TIERRA will make understanding this simulation a lot easier.

For those that already know TIERRA, the main differences between it and SALIS are:

  • the replacement of templates with key-lock instruction pairs
  • the addition of a SEEKER POINTER to all organisms

The seeker pointer is an attempt to bring extra spatial and temporal coherence to the simulation. Allocation, reads and writes will take more time when done between addresses that are far away, as a consequence of the SP having to travel those distances at a speed of 1 byte per update. In other words, in SALIS information can't travel faster than 1 byte per update (SALIS' speed of light, if you will).

To watch an introductory video about SALIS go here.

Follow SALIS on Reddit.


  • SALIS is an API, so an UI must be written to communicate with it
  • SALIS is written in C
  • SALIS must be compiled as a library (e.g.

Organisms consist of

  • One or two associated memory blocks
  • One instruction pointer
  • One seeker pointer
  • Four registers
  • A stack of configurable size (default is 8)


  • Newborn organisms are placed on top of the queue
  • Organisms are killed at the bottom of the queue
  • Organisms are killed whenever memory fills above 50%


In SALIS mutation occurs via cosmic rays: at every cycle a random 32 bit address is selected and a random instruction is written into it.

Instruction set

SALIS' organisms read a simple language similar to ASM. This language consists of 64 instructions, each with an associated name and symbol. Whenever an organism performs an invalid instruction it's considered a fault. When a fault is commited by any organism, the faulty instruction gets randomly replaced at that address and the organism's IP gets incremented.


  • Perform a search or attempt a jump without a following key
  • Writing to an allocated (but not owned) or invalid address
  • Reading (loading) from an invalid address
  • SP on address non-adjacent to child memory block while allocating
  • Swapping, freeing or splitting when not owning 2 memory blocks
  • Dividing by zero

Instruction set table

Name Sym. Val. Description
NOOP 00 No operation. Does nothing.
NOP0-3 0-3 01-04 No operation. Modifies registers to be used (r0x to r3x).
JMPB-F* () 05-06 Jump to lock matching following key.
ADRB-F* [] 07-08 Search for lock matching following key and store on r[0].
IFNZ ? 09 If r[0] is not zero, execute following instruction. Skip otherwise.
ALLB-F* {} 10-11 Allocate block of size stored on r[0]. Store its address on r[0].
BSWP* % 12 Swap parent and child memory blocks.
BCLR* | 13 Free child memory block.
SPLT* $ 14 Split. Child memory block becomes new organism.
ADDN + 15 Add (r[0] = r[1] + r[2]).
SUBN - 16 Subtract (r[0] = r[1] - r[2]).
MULN * 17 Multiply (r[0] = r[1] * r[2]).
DIVN* / 18 Divide (r[0] = r[1] / r[2]). Faults if divisor is zero.
INCN ^ 19 Increment (r[0]++).
DECN v 20 Decrement (r[0]--).
NOTN ! 21 Not (r[0] = !r[0]).
SHFL < 22 Shift left by 1 (r[0] << 1).
SHFR > 23 Shift right by 1 (r[0] >> 1).
ZERO z 24 Put zero (r[0] = 0).
UNIT u 25 Put one (r[0] = 1).
PSHN # 26 Push r[0] to stack.
POPN ~ 27 Pop from stack into r[0].
LOAD* . 28 Load instruction at address pointed by r[0] into r[1].
WRTE* : 29 Write instruction on r[1] to address pointed by r[0].
DUPL " 30 Duplicate value on r[0] into r[1].
SWAP x 31 Swap values on r[0] and r[1].
KEYA-P a-p 32-47 Keys.
LOKA-P A-P 48-63 Locks.

Instructions that may fault are marked with an asterisk (*) on the table above.

Instructions that modify values on registers may be followed by up to 3 register modifiers (r[0], r[1] and r[2]). By default, all registers are set to r0x.

Sample r[0] r[1] r[2] Meaning
+123 r1x r2x r3x r1x = r2x + r3x
-11 r1x r1x r0x r1x = r1x - r0x
* r0x r0x r0x r0x = r0x * r0x
!2 r2x --- --- r2x = !r2x
x01 r0x r1x --- swap r0x and r1x
]a1 r1x --- --- r1x = address of closest following LOKA
[b r0x --- --- r0x = address of closest previous LOKB

Building instructions

You'll need nothing but a C compiler (C89). If you want to build TSalis, you'll also need the NCurses development libraries. A sample makefile is provided for GNU Make. Just run make inside this directory and the salis library should compile as well as the tsalis executable. You may want to run sudo make install as well, in order to install the salis library as such:

$ git clone
$ cd salis/
$ make
$ sudo make install

To run, simply:

$ cd bin/
$ ./tsalis

Feel free to edit the makefile as needed. Code should compile easily on all platforms and on all C89 compliant compilers. If you run into any difficulties, please let me know!