feat(v4.0.0): a node looks before it writes; two neighbours no longer stop each other
MESH.md step 4, the fault found there, as ruled (section 7a): a node writes only to a neighbour that is reading, keeps what it takes in meanwhile, and loses and counts what it has no room for. Engine: two more addresses after a node's ports -- which ports have a neighbour waiting to write to it, which to read from it. Nucleus: (GATE) before every message; the messages waiting, a ring of 400 cells, dealt with when the node is idle. Of two neighbours the lower number may wait to write (ruled after it was built); NEIGHBOUR tells a node who is on each port. test_host_mesh.c, 44 checks: the case that stopped the nodes passes; six messages from each node to each at once all arrive; 800 at once, the nodes come to rest and every message arrived or was counted (287 arrived, 714 of all kinds let go). test_fabric.c: the two looks. Both widths, ASan+UBSan. POST: twelve cases handed HERE, a cell address on v4, to words that take a byte address, and so wrote into or read from the nucleus's code at cell HERE/4. Ruled: left out, marked OPEN, until HERE and the byte words are made to agree as its own step. POST is 538 cases. hosted-check on three ISAs, 538/538. Bare metal: logs/20261006-134817 (amd64), -135044 (aarch64), -135440 (riscv64). Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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rajames
co-authored by
Claude Opus 5.5
Claude Opus 5.5
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630d03fa4e
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-1
@@ -128,6 +128,98 @@ header CMOVE
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NONE: drop drop (ROUTE-DEFAULT) a! @ ;
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HIT: drop drop @+ pop drop ;
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\ LOOKING BEFORE WRITING (MESH.md section 7a). A write waits until the
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\ neighbour reads, and a node that is waiting to write reads nothing: two
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\ neighbours that each began to write to the other would wait for ever. So
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\ a node does not begin a message until it has looked, (GATE):
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\ - while any neighbour is waiting to write to it, it takes that message
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\ in and keeps it with the messages waiting, to deal with when it has
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\ nothing else to do;
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\ - then, if the neighbour it means to write to is waiting to read, it
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\ writes;
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\ - and if that neighbour is not, it writes all the same when the
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\ neighbour's number is the higher of the two, and otherwise looks
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\ again. Of two neighbours one only may wait to write to the other, and
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\ it is the lower: so those that wait are waiting on ever higher
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\ numbers, and the highest of them is not waiting to write; it is
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\ looking, and takes in what is being written to it.
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\ (WRITERS) and (READERS) are the node's two looks at its neighbours, a bit
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\ for each port. (NEAR) is the number of the node on each port, told by
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\ whoever wires it (NEIGHBOUR, quit.v4); a port not told of -- a device's
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\ -- is written to only when what is there is waiting to read.
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\
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\ THE MESSAGES WAITING are kept in (MQ) .. (MQ-END), one after another,
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\ going round: for each its seven words, the port it came on, and its text.
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\ (MQ-HEAD) is where the oldest begins, (MQ-TAIL) where the next will go,
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\ (MQ#) how many cells are taken. One that there is no room for is read to
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\ its end and let go, and (LOST) counts it.
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\ ( mask index -- bit )
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: (BIT)
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if Z -1 + FOR 2/ NEXT 1 and ;
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Z: drop 1 and ;
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\ ( mask -- index ) the lowest port in it; the mask is not zero
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: (LOW)
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0 push
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L: dup 1 and if UP drop drop pop ;
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UP: drop 2/ pop 1 + push jump L
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\ ( w -- ) one more cell of the messages waiting. B is kept.
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: (MQ!)
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(MQ-TAIL) a! @ a! !+
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a (MQ-END) xor if WRAP drop a jump SET
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WRAP: drop (MQ)
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SET: (MQ-TAIL) a! !
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(MQ#) a! @ 1 + ! ;
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\ ( -- w ) the oldest cell of the messages waiting, which goes
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: (MQ@)
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(MQ-HEAD) a! @ a! @+
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a (MQ-END) xor if WRAP drop a jump SET
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WRAP: drop (MQ)
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SET: (MQ-HEAD) a! !
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(MQ#) a! @ -1 + ! ;
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\ ( port to -- ) take in a message. B is at the port, by its address,
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\ and `to` is the message's first word, already read from it. A length
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\ below zero, or above what a message carries, is kept as -1 with no text:
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\ a longer one is read to its end first, so that what follows it is not
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\ taken for a message.
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: (TAKE)
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(MQ-HDR) a! !+ 5 FOR @b !+ UNEXT ! \ its seven words, and the port
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(MQ-HDR)+6 a! @ -if SIZED
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drop -1 (MQ-HDR)+6 a! ! 0 jump COUNTED
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SIZED: dup -1025 + -if LONG drop 3 + 2/ 2/ jump COUNTED
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LONG: drop 3 + 2/ 2/ -1 + FOR @b drop UNEXT -1 (MQ-HDR)+6 a! ! 0
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COUNTED: \ ( n ) how many words of text follow
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dup (MQ#) a! @ + -MQ-ROOM + -if FULL
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drop push
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(MQ-HDR) a! @ (MQ!) (MQ-HDR)+1 a! @ (MQ!) (MQ-HDR)+2 a! @ (MQ!) (MQ-HDR)+3 a! @ (MQ!)
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(MQ-HDR)+4 a! @ (MQ!) (MQ-HDR)+5 a! @ (MQ!) (MQ-HDR)+6 a! @ (MQ!) (MQ-HDR)+7 a! @ (MQ!)
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pop if NOTEXT -1 + FOR @b (MQ!) NEXT ;
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NOTEXT: drop ;
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FULL: drop if GONE -1 + FOR @b drop UNEXT jump LOSE
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GONE: drop
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LOSE: (LOST) a! @ 1 + ! ;
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\ ( port -- ) wait until a message may be begun on the port, by its
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\ address, taking in whatever is being written to this node meanwhile; and
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\ leave B at the port. The port is kept in (GATE-PORT), not on the stack:
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\ this is run with the stack as full as EMIT may be.
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: (GATE)
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(GATE-PORT) a! !
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L: (WRITERS) b! @b if QUIET
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(LOW) (PORT) + dup b! @b (TAKE) jump L
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QUIET: drop
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(GATE-PORT) a! @ (PORT) - (NEAR) + a! @ if ASK
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(ME) a! @ - -if GO jump ASK \ its number less this node's
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GO: drop (GATE-PORT) a! @ b! ; \ the neighbour's is the higher
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ASK: drop
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(READERS) b! @b (GATE-PORT) a! @ (PORT) - (BIT) if NOTYET
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drop (GATE-PORT) a! @ b! ; \ it is waiting to read
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NOTYET: drop jump L
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\ ( type -- ) words 1 to 5 of a message this node sends: from, type, and
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\ the three that are carried and not used yet. Its caller has put B at the
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\ port and sent word 0, whom it is to, and sends the length and the text.
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@@ -142,7 +234,7 @@ header CMOVE
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\ lowest. quit.v4 sets those two when text for this node arrives.
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: (FLUSH-OUT)
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(OUT^) a! @ (OUT) xor if NONE drop
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(PRINT-PORT) a! @ b! (PRINT-TO) a! @ !b
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(PRINT-PORT) a! @ (GATE) (PRINT-TO) a! @ !b
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2 (HDR)
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(OUT^) a! @ (OUT) - dup !b
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3 + 2/ 2/ -1 + (OUT) a!
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