I want to know if there is any difference between the two:
1) simple_port
data_valid : simple_port of bit is instance;
keep data_valid.hdl_path() == "data_valid_o";
event data_valid_f is fall(data_valid$) #sim;
on data_valid_f {
-- do some stuff
};
2) event_port
data_valid : event_port is instance;
keep data_valid.hdl_path() == "data_valid_o";
keep data_valid.edge() == fall;
on data_valid$ {
-- do some stuff
};
Thanks in advance!
Put simply, the event_port will detect glitches, i.e. zero time signal changes within a simulation cycle.
The value of the simple_port will be determined by the signal value at the end of the simulation cycle, no matter how many times it toggled before that.
Related
I'm trying to write a program to shift the key of a midi file. Basically, I just need to shift every note event by a given amount and live the rest unchanged. I found it easy to use MIKMIDI to read, parse, modify and write back the stream.
Unfortunately, I have a problem that I'm unable to solve. I've a loop in which I select the note events and add/subtract the desired shift value, but when I append the event in the output track I get a message from the MIKMIDI library:
"Warning: attempted to insert a NULL event".
The code I wrote is the following:
for event in inputTrack.events {
if event.eventType == .midiNoteMessage {
var tmpData = event.data
if (event.data[0] != 9) { // skip percussion channel
tmpData[1] = event.data[1] - shift
}
let outEvent = MIKMIDIEvent(timeStamp: event.timeStamp, midiEventType: .midiNoteMessage, data: tmpData)!
outputSeq.tracks[i].events.append(outEvent)
}
else {
outSeq.tracks[i].events.append(event)
}
}
BTW, the code works perfectly (the midi file is plays as expected), it is just that it takes minutes to execute in debugging mode due to the infinite sequence of warning messages printed in the debug screen.
Thanks!
UPDATE
I think I've figured out the solution. I explain it in this video. Basically, use timeoutWith, and some tricks with zip (within zip).
https://youtu.be/0A7C1oJSJDk
If I have a single observable like this:
A-1-2--B-3-4-5-C--D--6-7-E
I want to put the "numbers" as lower priority; it should wait until the "letters" is filled up (a group of 2 for example) OR a timeout is reached, and then it can emit. Maybe the following illustration (of the desired result) can help:
A------B-1-----C--D-2----E-3-4-5-6-7
I've been experimenting with some ideas... one of them: first step is to split that stream (groupBy), one containing letters, and the other containing numbers..., then "something in the middle" happen..., and finally those two (sub)streams get merged.
It's that "something in the middle" what I'm trying to figure out.
How to achieve it? Is that even possible with RxJS (ver 5.5.6)? If not, what's the closest one? I mean, what I want to avoid is having the "numbers" flooding the stream, and not giving enough chance for the "letters" to be processed in timely manner.
Probably this video I made of my efforts so far can clarify as well:
Original problem statement: https://www.youtube.com/watch?v=mEmU4JK5Tic
So far: https://www.youtube.com/watch?v=HWDI9wpVxJk&feature=youtu.be
The problem with my solution so far (delaying each emission in "numbers" substream using .delay) is suboptimal, because it keeps clocking at slow pace (10 seconds) even after the "characters" (sub)stream has ended (not completed -- no clear boundary here -- just not getting more value for indeterminate amount of time). What I really need is, to have the "numbers" substream raise its pace (to 2 seconds) once that happen.
Unfortunately I don't know RxJs5 that much and use xstream myself (authored by one of the contributor to RxJS5) which is a little bit simpler in terms of the number of operators.
With this I crafted the following example:
(Note: the operators are pretty much the same as in Rx5, the main difference is with flatten wich is more or less like switch but seems to handle synchronous streams differently).
const xs = require("xstream").default;
const input$ = xs.of("A",1,2,"B",3,4,5,"C","D",6,7,"E");
const initialState = { $: xs.never(), count: 0, buffer: [] };
const state$ = input$
.fold((state, value) => {
const t = typeof value;
if (t === "string") {
return {
...state,
$: xs.of(value),
count: state.count + 1
};
}
if (state.count >= 2) {
const l = state.buffer.length;
return {
...state,
$: l > 0 ? xs.of(state.buffer[0]) : xs.of(value) ,
count: 0,
buffer: state.buffer.slice(1).concat(value)
};
}
return {
...state,
$: xs.never(),
buffer: state.buffer.concat(value),
};
}, initialState);
xs
.merge(
state$
.map(s => s.$),
state$
.last()
.map(s => xs.of.apply(xs, s.buffer))
)
.flatten()
.subscribe({
next: console.log
});
Which gives me the result you are looking for.
It works by folding the stream on itself, looking at the type of values and emitting a new stream depending on it. When you need to wait because not enough letters were dispatched I emit an emptystream (emits no value, no errors, no complete) as a "placeholder".
You could instead of emitting this empty stream emit something like
xs.empty().endsWith(xs.periodic(timeout)).last().mapTo(value):
// stream that will emit a value only after a specified timeout.
// Because the streams are **not** flattened concurrently you can
// use this as a "pending" stream that may or may not be eventually
// consumed
where value is the last received number in order to implement timeout related conditions however you would then need to introduce some kind of reflexivity with either a Subject in Rx or xs.imitate with xstream because you would need to notify your state that your "pending" stream has been consumed wich makes the communication bi-directionnal whereas streams / observables are unidirectionnal.
The key here the use of timeoutWith, to switch to the more aggresive "pacer", when the "events" kicks in. In this case the "event" is "idle detected in the higher-priority stream".
The video: https://youtu.be/0A7C1oJSJDk
In Dining Philosophers implementation with a monitor, why does the putdown()
operation call the test() operation twice?
procedure take_chopsticks(i)
{
DOWN(me);
pflag[i] := HUNGRY;
test[i];
UP(me);
DOWN(s[i]) }
void test(i)
{
if ( pflag[i] == HUNGRY
&& pflag[i-1] != EAT
&& pflag[i+1] != EAT)
then
{
pflag[i] := EAT;
UP(s[i])
}
}
void drop_chopsticks(int i)
{
DOWN(me);
test(i-1);
test(i+1);
UP(me);
}
It calls it twice because each chopstick is considered it's own ressource. Therefore you need to 'signal()' that both chopstick are individually available for pickup now.
I only work on theoretical code for this problem but I am not sure you're reference to chopstick 'i-1' and 'i+1' is correct. I would need to see your initialization and the rest of your code, but conventional solutions usually refer to chopsticks for philosopher i as (i+1) for right chopstick and (i+4) for his left chopstick, in the case of 5 philosophers.
In the game I'm working on I would like to give users the possibility to select between asynchronous and real-time turn-based matches. The one thing I'm missing from the latter is how do I know who's got the first turn. I'm trying to find a way to detect who's got connected first and set that player's turn automatically. Unfortunately, it seems that both players get connected at the same time since right after finding a match expectedPlayersCount yields 1 for both players and in the didChangeState event that same variable yields 0 for both of them too. So I have no way to tell who's got first to the match since it seems that it all happens simultaneously.
As a temporary fix, I'm just using their IDs. The one with the lowest ID is the one having the first turn. However, I'm trying to find a better way since with this approach player A will always get the first turn when playing against player B and that represents a small advantage in my game.
This method is what I call when starting a new game. I pass a realTime bool value to specify whether the game returned by the game center wrapper should be a GKMatch or GKTurnBasedMatch.
//Calculate the level group to find other players in the same group
NSInteger levelGroup = (self.player.levelValue / STLevelSkillInterval) * STLevelSkillInterval;
//Find a match for the local player
[self.gameCenter findMatchWithPlayerAttributes:levelGroup realTime:realTime group:0 onCompletion:^(GKTurnBasedMatch *turnMatch, GKMatch *realTimeMatch) {
[self handleTurnMatchFound:turnMatch realTimeMatch:realTimeMatch completionBlock:onCompletion];
}];
...
This method here is the responsible to handle game center response after finding match. The create and synchronize method stores a match instance in CoreData and also fills its data by fetching the corresponding info from Game Center and my backend. So if at the time of that's done the expected player count reached 0, I call the completion block immediately since the match can begin. Otherwise I just store the completion block so I can use it later when the other player connects to the match. The problem in that part is that it never reaches 0, not for any of the two players.
- (void)handleTurnMatchFound:(GKTurnBasedMatch *)turnMatch realTimeMatch:(GKMatch *)realTimeMatch completionBlock:(void(^)(STMatch *match, NSError *error))onCompletion
{
if (turnMatch != nil)
{
[self createAndSynchronizeLocalMatch:turnMatch onCompletion:^(STMatch *localMatch) {
onCompletion(localMatch, nil);
}];
}
else if (realTimeMatch != nil)
{
[self createAndSynchronizeRealTimeLocalMatch:realTimeMatch onCompletion:^(STMatch *localMatch) {
if (realTimeMatch.expectedPlayerCount == 0)
{
onCompletion(localMatch, nil);
}
else
{
self.findRealTimeMatchCompletionBlock = onCompletion;
}
}];
}
else
{
onCompletion(nil, nil);
}
}
...
This is the method that handles player's state changes. So basically here I just update the local instance of the real time match with values from the connected player and then I call the completion block stored earlier.
- (void)match:(GKMatch *)match player:(NSString *)playerID didChangeState:(GKPlayerConnectionState)state
{
if (state == GKPlayerStateConnected)
{
STMatchParticipant *placeholderParticipant = [self.realTimeMatch getMatchParticipantWithPlayerId:nil];
placeholderParticipant.playerId = playerID;
placeholderParticipant.statusValue = GKTurnBasedParticipantStatusActive;
//This will sync the information for the connected player only
[self syncAllPlayerInfoForRealTimeMatchOnCompletion:^(NSArray *players) {
self.findRealTimeMatchCompletionBlock(self.realTimeMatch, nil);
}];
}
else
{
//Notify the observers that the participant has disconnected from the match
STMatchParticipant *participant = [self.realTimeMatch getMatchParticipantWithPlayerId:playerID];
for (id<STTurnBasedMatchDelegate> observer in self.matchesObservers)
{
if ([observer respondsToSelector:#selector(realTimeMatch:participantDidDisconnect:)])
{
[observer realTimeMatch:self.realTimeMatch participantDidDisconnect:participant];
}
}
}
}
I would appreciate any comments.
Instead of trying to determine who got connected first, why don't you just have all the players pick a random number using arc4random ?
int randomNumber = arc4random%1000000;
The player with the biggest number can play first. You will have to make sure all the players send each other their random numbers so everyone can compare and decide who is first.
In the above example, the range would be upto 1 million, so the odds of two players picking the same random number is low.
If two players do pick the same random number, you could compute the hash of their playerId's, and have the player with the larger hash be first.
if ([GKLocalPlayer localPlayer].playerID.hash > otherPlayerId.hash )
The chances of a hash collision occurring are very low, since the playerId strings are short. You can still check for this collision and handle it appropriately (maybe by hashing again ;) ).
proces P0: proces P1:
while (true) while (true)
{ {
flag[0] = true; flag[1] = true;
while (flag[1]) while (flag[0])
{ {
flag[0] = false; flag[1] = false;
flag[0] = true; flag[1] = true;
} }
crit0(); crit1();
flag[0] = false; flag[1] = false;
rem0(); rem1();
} }
Could someone give me a scenario with context switches to prove if the above stated code meets the requirements of progress and bounded waiting.
And can anyone give me some tips about how to detect if a code meets the requirements of progress or bounded waiting(and maybe including starvation,deadlock and after-you after you)
The two processes are happening at the same time.
The trick here is that since there is nothing truly synchronizing the two programs, something could happen between lines. On the same note, it's possible things happen at the same time.
To see how this can be an issue, think about this situation...
What would happen if the first flag[0] = true and the first flag[1] = true happened on P0/P1 at exactly the same time?
Both process 1 and process 2 would be stuck in a while loop. How would they exit the while loop? One process would have to check while(flag[other]) at exactly the same moment the other process set their flag[me] to true. This is a very narrow time span. It's the equivalent of rolling dice over and over and not continuing until you hit a certain number.
This is why we need something of a higher level to handle the synchronization for us - real locks and the like.
edit: Oh, one other thing. You may want to check to see if the read/write operations are thread safe. What happens if the system tries to write to the bit the same time it tries to read it?
edit2: FYI - http://msdn.microsoft.com/en-us/library/aa645755(v=VS.71).aspx