Heterostasis (cybernetics)

Heterostasis is a medical term. It is a neologism coined by Walter Cannon intended to connote an alternative but related meaning to its lexical sibling Homeostasis, which means 'same state'. Any device, organ, system or organism capable of Heterostasis (multistable behavior) can be represented by an abstract state machine composed of a characteristic set of related, interconnected states, linked dynamically by change processes allowing transition between states.

Although the term 'Heterostasis' is an obvious rearrangement (by syntactically substituting the prefix 'Hetero-' for its dichotome 'Homeo-', and likewise swapping the semantic reference, from 'same'/'single' to 'different'/'many'), the endocrinologist Hans Selye[1] is generally credited with its invention. An excellent overview of the two concepts is contained in the Cambridge Handbook of Psychophysiology, Chapter 19.[2] Selye's ideas were used by Gunther et al.,[3] in which dimensionless numbers (allometric invariance analysis) were used to investigate the existence of heterostasis in canine cardiovascular systems.

Alternative terminology

The equivalent term Allostasis is used in biological contexts, where state change is analog (continuous), but Heterostasis is sometimes preferred for systems which possess a finite number of distinct (discrete) internal states, such as those containing computational processes. The term Servomechanism is usually used in industrial/mechanical situations (non-biological and non-computational) where it often applies to analog state change, e.g. in a Direct Current Servomotor.

gollark: All numbers are two's complement because bee you.
gollark: The rest of the instruction consists of variable-width (for fun) target specifiers. The first N target specifiers in an operation are used as destinations and the remaining ones as sources. N varies per opcode. They can be of the form `000DDD` (pop/push from/to stack index DDD), `001EEE` (peek stack index EEE if source, if destination then push onto EEE if it is empty), `010FFFFFFFF` (8-bit immediate value FFFFFFFF; writes are discarded), `011GGGGGGGGGGGGGGGG` (16-bit immediate value GGGGGGGGGGGGGGGG; writes are also discarded), `100[H 31 times]` (31-bit immediate because bee you), `101IIIIIIIIIIIIIIII` (16 bits of memory location relative to the base memory address register of the stack the operation is conditional on), `110JJJJJJJJJJJJJJJJ` (16 bit memory location relative to the top value on that stack instead), `1111LLLMMM` (memory address equal to base memory address of stack LLL plus top of stack MMM), or `1110NNN` (base memory address register of stack MMM).Opcodes (numbered from 0 in order): MOV (1 source, as many destinations as can be parsed validly; the value is copied to all of them), ADD (1 destination, multiple sources), JMP (1 source), NOT (same as MOV), WR (write to output port; multiple sources, first is port number), RE (read from input port; one source for port number, multiple destinations), SUB, AND, OR, XOR, SHR, SHL (bitwise operations), MUL, ROR, ROL, NOP, MUL2 (multiplication with two outputs).
gollark: osmarksISA™️-2028 is a VLIW stack machine. Specifically, it executes a 384-bit instruction composed of 8 48-bit operations in parallel. There are 8 stacks, for safety. Each stack also has an associated base memory address register, which is used in some "addressing modes". Each stack holds 64-bit integers; popping/peeking an empty stack simply returns 0, and the stacks can hold at most 32 items. Exceeding a stack's capacity is runtime undefined behaviour. The operation encoding is: `AABBBCCCCCCCCC`:A = 2-bit conditional operation mode - 0 is "run unconditionally", 1 is "run if top value on stack is 0", 2 is "run if not 0", 3 is "run if first bit is ~~negative~~ 1".B = 3-bit index for the stack to use for the conditional.C = 9-bit opcode (for extensibility).
gollark: By "really fast", I mean "in a few decaminutes, probably".
gollark: I suppose I could just specify it really fast.

References
  1. Selye, H. (1973) Homeostasis and Heterostasis. Perspectives in Biology and Medicine, 16, 441-445
  2. Cacciopo, J.T., Tassinary, L.G., Berntson, G.G. (Eds.)(2000)Handbook of Psychophysiology, 2nd ed. Cambridge University Press
  3. Gunther, B., Morgado, E., Jimenez, R.F. (2003) Homeostasis to Heterostasis: from invariant to dimensionless numbers. Biol. Res. 2003;36(2):211-221
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