Problems With The Counter Machine Model
- The problems are discussed in detail in the article Random access machine. The problems fall into two major classes and a third "inconvenience" class:
(1) Unbounded capacities of registers versus bounded capacities of state-machine instructions: How will the machine create constants larger than the capacity of its finite state machine?
(2) Unbounded numbers of registers versus bounded numbers of state-machine instructions: How will the machine access registers with address-numbers beyond the reach/capability of its finite state machine?
(3) The fully reduced models are cumbersome:
Shepherdson and Sturgis (1963) are unapologetic about their 6-instruction set. They have made their choice based on "ease of programming... rather than economy" (p. 219 footnote 1).
Shepherdson and Sturgis' instructions ( indicates "contents of register r"):
-
- INCREMENT ( r ) ; +1 → r
- DECREMENT ( r ) ; -1 → r
- CLEAR ( r ) ; 0 → r
- COPY ( rs to rd ) ; → rd
- JUMP-UNCONDITIONAL to instruction Iz
- JUMP IF =0 to instruction Iz
Minsky (1967) expanded his 2-instruction set { INC (z), JZDEC (r, Iz) } to { CLR (r), INC (r), JZDEC (r, Iz), J (Iz) } before his proof that a "Universal Program Machine" can be built with only two registers (p. 255ff).
Read more about this topic: Counter Machine
Famous quotes containing the words problems, counter, machine and/or model:
“The three great problems of this century, the degradation of man in the proletariat, the subjection of women through hunger, the atrophy of the child by darkness.”
—Victor Hugo (1802–1885)
“I’d take the bus downtown with my mother, and the big thing was to sit at the counter and get an orange drink and a tuna sandwich on toast. I thought I was living large!... When I was at the Ritz with the publisher a few months ago, I did think, “Oh my God, I’m in the Ritz tearoom.” ... The person who was so happy to sit at the Woolworths counter is now sitting at the Ritz, listening to the harp, and wondering what tea to order.... [ellipsis in source] Am I awake?”
—Connie Porter (b. 1959)
“Much that is natural, to the will must yield.
Men manufacture both machine and soul,
And use what they imperfectly control
To dare a future from the taken routes.”
—Thom Gunn (b. 1929)
“When Titian was mixing brown madder,
His model was posed up a ladder.
Said Titian, “That position
Calls for coition,”
So he lept up the ladder and had her.”
—Anonymous.