ProvaTeorica 2005.11.04 - Revision history

TomOgn: /* Esercizio 1 */

2014-05-18T19:23:56Z

Esercizio 1

TomOgn: /* Esercizio 1 */

2014-05-14T21:20:37Z

Esercizio 1

TomOgn: /* Esercizio 3 */

2014-05-14T10:02:55Z

Esercizio 3

TomOgn: Created page with "=[http://www.cs.unibo.it/~renzo/so/compiti/2005-11-04.con.pdf TESTO COMPITO]= =CONCORRENZA= ==Esercizio 1== monitor casino { bool playing, exEquo; ..."

2014-05-13T20:51:22Z

Created page with "=[http://www.cs.unibo.it/~renzo/so/compiti/2005-11-04.con.pdf TESTO COMPITO]= =CONCORRENZA= ==Esercizio 1== <syntaxhighlight lang="C"> monitor casino { bool playing, exEquo; ..."

New page

=[http://www.cs.unibo.it/~renzo/so/compiti/2005-11-04.con.pdf TESTO COMPITO]=
=CONCORRENZA=
==Esercizio 1==
<syntaxhighlight lang="C">
monitor casino
{
bool playing, exEquo;
int max, n, leaving;
condition wantToPlay, player;

playing = exEquo = false;
n = 0;

void misiedo()
{
if (playing)
wantToPlay.wait();
// Rendez-vous mechanism
if (++n < 5)
player.wait();
else
{
playing = true;
max = 0;
}
player.signal();
}

int gioca(int number)
{
if (number == max)
exEquo = true;
else if (number > max)
{
exEquo = false;
max = number;
}
if (--n > 0)
player.wait();
else
leaving = 5;
player.signal();
return (!exEquo && number == max)? 4 : -1;
}

void mialzo()
{
if (--leaving == 0)
playing = false;
wantToPlay.signal();
}
}
</syntaxhighlight>
==Esercizio 2==
<syntaxhighlight lang="Python">
def ssend2(m, d1, d2):
msg = ( SND, getpid(), d1, d2, m )
asend(msg, server)
return arecv(server)

def sreceive():
msg = ( RCV, getpid(), None, None, None )
asend(msg, server)
return arecv(server)

def server():
while True:
flag, src, d1, d2, msg = arecv(*)
if flag == RCV:
msg, sender, _, _ = dbSnd.retrieve(query = '(?, ?, src, ?) or (?, ?, ?, src)')
if msg:
asend(msg, src)
asend(src, sender)
else:
dbRcv.insert(src)
else:
if dbRcv.retrieve(d1):
asend(msg, d1)
asend(d1, src)
elif dbRcv.retrieve(d2):
asend(msg, d2)
asend(d2, src)
else:
dbSnd.insert((msg, src, d1, d2))
</syntaxhighlight>
==Esercizio 3==
<syntaxhighlight lang="Python">
global = 3

CSenter:
while True:
local = 2
QR(global, local) # QR(x,y) = <y1=x%y; x1=x/y; x=x1; y=y1;>
if local == 3/2:
break

CSexit:
global = 3

'''
Osservazioni:
(1) La funzione atomica risulta idonea a sostituire la Test&Set.
(2) La variabile globale assume i seguenti valori:
3, quando la Critical Section e' libera;
1, quando la Critical Section e' !libera.
(3) Si alternano i seguenti 4 stati (<global, local>):
(da libero ad occupato) <3, 2> --> <1, 3/2>
(da occupato ad occupato) <1, 2> --> <1, 1/2>
'''
</syntaxhighlight>

@@ Line 6: / Line 6: @@
+{
 	bool playing, exEquo;
-	int max, n, leaving, waiting;
+	int max, n, waiting;
 	condition wantToPlay, player;
@@ Line 42: / Line 42: @@
 			player.wait();
 		else
-			leaving = 5;
+			n = 5;
 		player.signal();
 		return (!exEquo && number == max)? 4 : -1;
@@ Line 49: / Line 49: @@
 	void mialzo()
+	{
-		if (--leaving == 0)
+		if (--n == 0)
+		{
 			while (waiting > 0 && n < 4)

@@ Line 6: / Line 6: @@
+{
 	bool playing, exEquo;
-	int max, n, leaving;
+	int max, n, leaving, waiting;
 	condition wantToPlay, player;
 	playing = exEquo = false;
-	n = 0;
+	n = waiting = 0;
 	void misiedo()
+	{
 		if (playing)
 			wantToPlay.wait();
-		// Rendez-vous mechanism
+			waiting--;
 		if (++n < 5)
 			player.wait();
@@ Line 22: / Line 25: @@
+		{
 			playing = true;
 			max = 0;
+		}
 		player.signal();
@@ Line 47: / Line 50: @@
+	{
 		if (--leaving == 0)
-			playing = false;
-		wantToPlay.signal();
+			while (waiting > 0 && n < 4)
+	}
+}
 </syntaxhighlight>
 ==Esercizio 2==
 <syntaxhighlight lang="Python">