linear arithmetic splits certain operators (e.g. min, max, abs)
header {* \section{Examples} *}
theory OG_Examples imports OG_Syntax begin
subsection {* Mutual Exclusion *}
subsubsection {* Peterson's Algorithm I*}
text {* Eike Best. "Semantics of Sequential and Parallel Programs", page 217. *}
record Petersons_mutex_1 =
pr1 :: nat
pr2 :: nat
in1 :: bool
in2 :: bool
hold :: nat
lemma Petersons_mutex_1:
"\<parallel>- .{\<acute>pr1=0 \<and> \<not>\<acute>in1 \<and> \<acute>pr2=0 \<and> \<not>\<acute>in2 }.
COBEGIN .{\<acute>pr1=0 \<and> \<not>\<acute>in1}.
WHILE True INV .{\<acute>pr1=0 \<and> \<not>\<acute>in1}.
DO
.{\<acute>pr1=0 \<and> \<not>\<acute>in1}. \<langle> \<acute>in1:=True,,\<acute>pr1:=1 \<rangle>;;
.{\<acute>pr1=1 \<and> \<acute>in1}. \<langle> \<acute>hold:=1,,\<acute>pr1:=2 \<rangle>;;
.{\<acute>pr1=2 \<and> \<acute>in1 \<and> (\<acute>hold=1 \<or> \<acute>hold=2 \<and> \<acute>pr2=2)}.
AWAIT (\<not>\<acute>in2 \<or> \<not>(\<acute>hold=1)) THEN \<acute>pr1:=3 END;;
.{\<acute>pr1=3 \<and> \<acute>in1 \<and> (\<acute>hold=1 \<or> \<acute>hold=2 \<and> \<acute>pr2=2)}.
\<langle>\<acute>in1:=False,,\<acute>pr1:=0\<rangle>
OD .{\<acute>pr1=0 \<and> \<not>\<acute>in1}.
\<parallel>
.{\<acute>pr2=0 \<and> \<not>\<acute>in2}.
WHILE True INV .{\<acute>pr2=0 \<and> \<not>\<acute>in2}.
DO
.{\<acute>pr2=0 \<and> \<not>\<acute>in2}. \<langle> \<acute>in2:=True,,\<acute>pr2:=1 \<rangle>;;
.{\<acute>pr2=1 \<and> \<acute>in2}. \<langle> \<acute>hold:=2,,\<acute>pr2:=2 \<rangle>;;
.{\<acute>pr2=2 \<and> \<acute>in2 \<and> (\<acute>hold=2 \<or> (\<acute>hold=1 \<and> \<acute>pr1=2))}.
AWAIT (\<not>\<acute>in1 \<or> \<not>(\<acute>hold=2)) THEN \<acute>pr2:=3 END;;
.{\<acute>pr2=3 \<and> \<acute>in2 \<and> (\<acute>hold=2 \<or> (\<acute>hold=1 \<and> \<acute>pr1=2))}.
\<langle>\<acute>in2:=False,,\<acute>pr2:=0\<rangle>
OD .{\<acute>pr2=0 \<and> \<not>\<acute>in2}.
COEND
.{\<acute>pr1=0 \<and> \<not>\<acute>in1 \<and> \<acute>pr2=0 \<and> \<not>\<acute>in2}."
apply oghoare
--{* 104 verification conditions. *}
apply auto
done
subsubsection {*Peterson's Algorithm II: A Busy Wait Solution *}
text {* Apt and Olderog. "Verification of sequential and concurrent Programs", page 282. *}
record Busy_wait_mutex =
flag1 :: bool
flag2 :: bool
turn :: nat
after1 :: bool
after2 :: bool
lemma Busy_wait_mutex:
"\<parallel>- .{True}.
\<acute>flag1:=False,, \<acute>flag2:=False,,
COBEGIN .{\<not>\<acute>flag1}.
WHILE True
INV .{\<not>\<acute>flag1}.
DO .{\<not>\<acute>flag1}. \<langle> \<acute>flag1:=True,,\<acute>after1:=False \<rangle>;;
.{\<acute>flag1 \<and> \<not>\<acute>after1}. \<langle> \<acute>turn:=1,,\<acute>after1:=True \<rangle>;;
.{\<acute>flag1 \<and> \<acute>after1 \<and> (\<acute>turn=1 \<or> \<acute>turn=2)}.
WHILE \<not>(\<acute>flag2 \<longrightarrow> \<acute>turn=2)
INV .{\<acute>flag1 \<and> \<acute>after1 \<and> (\<acute>turn=1 \<or> \<acute>turn=2)}.
DO .{\<acute>flag1 \<and> \<acute>after1 \<and> (\<acute>turn=1 \<or> \<acute>turn=2)}. SKIP OD;;
.{\<acute>flag1 \<and> \<acute>after1 \<and> (\<acute>flag2 \<and> \<acute>after2 \<longrightarrow> \<acute>turn=2)}.
\<acute>flag1:=False
OD
.{False}.
\<parallel>
.{\<not>\<acute>flag2}.
WHILE True
INV .{\<not>\<acute>flag2}.
DO .{\<not>\<acute>flag2}. \<langle> \<acute>flag2:=True,,\<acute>after2:=False \<rangle>;;
.{\<acute>flag2 \<and> \<not>\<acute>after2}. \<langle> \<acute>turn:=2,,\<acute>after2:=True \<rangle>;;
.{\<acute>flag2 \<and> \<acute>after2 \<and> (\<acute>turn=1 \<or> \<acute>turn=2)}.
WHILE \<not>(\<acute>flag1 \<longrightarrow> \<acute>turn=1)
INV .{\<acute>flag2 \<and> \<acute>after2 \<and> (\<acute>turn=1 \<or> \<acute>turn=2)}.
DO .{\<acute>flag2 \<and> \<acute>after2 \<and> (\<acute>turn=1 \<or> \<acute>turn=2)}. SKIP OD;;
.{\<acute>flag2 \<and> \<acute>after2 \<and> (\<acute>flag1 \<and> \<acute>after1 \<longrightarrow> \<acute>turn=1)}.
\<acute>flag2:=False
OD
.{False}.
COEND
.{False}."
apply oghoare
--{* 122 vc *}
apply auto
done
subsubsection {* Peterson's Algorithm III: A Solution using Semaphores *}
record Semaphores_mutex =
out :: bool
who :: nat
lemma Semaphores_mutex:
"\<parallel>- .{i\<noteq>j}.
\<acute>out:=True ,,
COBEGIN .{i\<noteq>j}.
WHILE True INV .{i\<noteq>j}.
DO .{i\<noteq>j}. AWAIT \<acute>out THEN \<acute>out:=False,, \<acute>who:=i END;;
.{\<not>\<acute>out \<and> \<acute>who=i \<and> i\<noteq>j}. \<acute>out:=True OD
.{False}.
\<parallel>
.{i\<noteq>j}.
WHILE True INV .{i\<noteq>j}.
DO .{i\<noteq>j}. AWAIT \<acute>out THEN \<acute>out:=False,,\<acute>who:=j END;;
.{\<not>\<acute>out \<and> \<acute>who=j \<and> i\<noteq>j}. \<acute>out:=True OD
.{False}.
COEND
.{False}."
apply oghoare
--{* 38 vc *}
apply auto
done
subsubsection {* Peterson's Algorithm III: Parameterized version: *}
lemma Semaphores_parameterized_mutex:
"0<n \<Longrightarrow> \<parallel>- .{True}.
\<acute>out:=True ,,
COBEGIN
SCHEME [0\<le> i< n]
.{True}.
WHILE True INV .{True}.
DO .{True}. AWAIT \<acute>out THEN \<acute>out:=False,, \<acute>who:=i END;;
.{\<not>\<acute>out \<and> \<acute>who=i}. \<acute>out:=True OD
.{False}.
COEND
.{False}."
apply oghoare
--{* 20 vc *}
apply auto
done
subsubsection{* The Ticket Algorithm *}
record Ticket_mutex =
num :: nat
nextv :: nat
turn :: "nat list"
index :: nat
lemma Ticket_mutex:
"\<lbrakk> 0<n; I=\<guillemotleft>n=length \<acute>turn \<and> 0<\<acute>nextv \<and> (\<forall>k l. k<n \<and> l<n \<and> k\<noteq>l
\<longrightarrow> \<acute>turn!k < \<acute>num \<and> (\<acute>turn!k =0 \<or> \<acute>turn!k\<noteq>\<acute>turn!l))\<guillemotright> \<rbrakk>
\<Longrightarrow> \<parallel>- .{n=length \<acute>turn}.
\<acute>index:= 0,,
WHILE \<acute>index < n INV .{n=length \<acute>turn \<and> (\<forall>i<\<acute>index. \<acute>turn!i=0)}.
DO \<acute>turn:= \<acute>turn[\<acute>index:=0],, \<acute>index:=\<acute>index +1 OD,,
\<acute>num:=1 ,, \<acute>nextv:=1 ,,
COBEGIN
SCHEME [0\<le> i< n]
.{\<acute>I}.
WHILE True INV .{\<acute>I}.
DO .{\<acute>I}. \<langle> \<acute>turn :=\<acute>turn[i:=\<acute>num],, \<acute>num:=\<acute>num+1 \<rangle>;;
.{\<acute>I}. WAIT \<acute>turn!i=\<acute>nextv END;;
.{\<acute>I \<and> \<acute>turn!i=\<acute>nextv}. \<acute>nextv:=\<acute>nextv+1
OD
.{False}.
COEND
.{False}."
apply oghoare
--{* 35 vc *}
apply simp_all
--{* 21 vc *}
apply(tactic {* ALLGOALS Clarify_tac *})
--{* 11 vc *}
apply simp_all
apply(tactic {* ALLGOALS Clarify_tac *})
--{* 10 subgoals left *}
apply(erule less_SucE)
apply simp
apply simp
--{* 9 subgoals left *}
apply(case_tac "i=k")
apply force
apply simp
apply(case_tac "i=l")
apply force
apply force
--{* 8 subgoals left *}
prefer 8
apply force
apply force
--{* 6 subgoals left *}
prefer 6
apply(erule_tac x=i in allE)
apply fastsimp
--{* 5 subgoals left *}
prefer 5
apply(tactic {* ALLGOALS (case_tac "j=k") *})
--{* 10 subgoals left *}
apply simp_all
apply(erule_tac x=k in allE)
apply force
--{* 9 subgoals left *}
apply(case_tac "j=l")
apply simp
apply(erule_tac x=k in allE)
apply(erule_tac x=k in allE)
apply(erule_tac x=l in allE)
apply force
apply(erule_tac x=k in allE)
apply(erule_tac x=k in allE)
apply(erule_tac x=l in allE)
apply force
--{* 8 subgoals left *}
apply force
apply(case_tac "j=l")
apply simp
apply(erule_tac x=k in allE)
apply(erule_tac x=l in allE)
apply force
apply force
apply force
--{* 5 subgoals left *}
apply(erule_tac x=k in allE)
apply(erule_tac x=l in allE)
apply(case_tac "j=l")
apply force
apply force
apply force
--{* 3 subgoals left *}
apply(erule_tac x=k in allE)
apply(erule_tac x=l in allE)
apply(case_tac "j=l")
apply force
apply force
apply force
--{* 1 subgoals left *}
apply(erule_tac x=k in allE)
apply(erule_tac x=l in allE)
apply(case_tac "j=l")
apply force
apply force
done
subsection{* Parallel Zero Search *}
text {* Synchronized Zero Search. Zero-6 *}
text {*Apt and Olderog. "Verification of sequential and concurrent Programs" page 294: *}
record Zero_search =
turn :: nat
found :: bool
x :: nat
y :: nat
lemma Zero_search:
"\<lbrakk>I1= \<guillemotleft> a\<le>\<acute>x \<and> (\<acute>found \<longrightarrow> (a<\<acute>x \<and> f(\<acute>x)=0) \<or> (\<acute>y\<le>a \<and> f(\<acute>y)=0))
\<and> (\<not>\<acute>found \<and> a<\<acute> x \<longrightarrow> f(\<acute>x)\<noteq>0) \<guillemotright> ;
I2= \<guillemotleft>\<acute>y\<le>a+1 \<and> (\<acute>found \<longrightarrow> (a<\<acute>x \<and> f(\<acute>x)=0) \<or> (\<acute>y\<le>a \<and> f(\<acute>y)=0))
\<and> (\<not>\<acute>found \<and> \<acute>y\<le>a \<longrightarrow> f(\<acute>y)\<noteq>0) \<guillemotright> \<rbrakk> \<Longrightarrow>
\<parallel>- .{\<exists> u. f(u)=0}.
\<acute>turn:=1,, \<acute>found:= False,,
\<acute>x:=a,, \<acute>y:=a+1 ,,
COBEGIN .{\<acute>I1}.
WHILE \<not>\<acute>found
INV .{\<acute>I1}.
DO .{a\<le>\<acute>x \<and> (\<acute>found \<longrightarrow> \<acute>y\<le>a \<and> f(\<acute>y)=0) \<and> (a<\<acute>x \<longrightarrow> f(\<acute>x)\<noteq>0)}.
WAIT \<acute>turn=1 END;;
.{a\<le>\<acute>x \<and> (\<acute>found \<longrightarrow> \<acute>y\<le>a \<and> f(\<acute>y)=0) \<and> (a<\<acute>x \<longrightarrow> f(\<acute>x)\<noteq>0)}.
\<acute>turn:=2;;
.{a\<le>\<acute>x \<and> (\<acute>found \<longrightarrow> \<acute>y\<le>a \<and> f(\<acute>y)=0) \<and> (a<\<acute>x \<longrightarrow> f(\<acute>x)\<noteq>0)}.
\<langle> \<acute>x:=\<acute>x+1,,
IF f(\<acute>x)=0 THEN \<acute>found:=True ELSE SKIP FI\<rangle>
OD;;
.{\<acute>I1 \<and> \<acute>found}.
\<acute>turn:=2
.{\<acute>I1 \<and> \<acute>found}.
\<parallel>
.{\<acute>I2}.
WHILE \<not>\<acute>found
INV .{\<acute>I2}.
DO .{\<acute>y\<le>a+1 \<and> (\<acute>found \<longrightarrow> a<\<acute>x \<and> f(\<acute>x)=0) \<and> (\<acute>y\<le>a \<longrightarrow> f(\<acute>y)\<noteq>0)}.
WAIT \<acute>turn=2 END;;
.{\<acute>y\<le>a+1 \<and> (\<acute>found \<longrightarrow> a<\<acute>x \<and> f(\<acute>x)=0) \<and> (\<acute>y\<le>a \<longrightarrow> f(\<acute>y)\<noteq>0)}.
\<acute>turn:=1;;
.{\<acute>y\<le>a+1 \<and> (\<acute>found \<longrightarrow> a<\<acute>x \<and> f(\<acute>x)=0) \<and> (\<acute>y\<le>a \<longrightarrow> f(\<acute>y)\<noteq>0)}.
\<langle> \<acute>y:=(\<acute>y - 1),,
IF f(\<acute>y)=0 THEN \<acute>found:=True ELSE SKIP FI\<rangle>
OD;;
.{\<acute>I2 \<and> \<acute>found}.
\<acute>turn:=1
.{\<acute>I2 \<and> \<acute>found}.
COEND
.{f(\<acute>x)=0 \<or> f(\<acute>y)=0}."
apply oghoare
--{* 98 verification conditions *}
apply auto
--{* auto takes about 3 minutes !! *}
done
text {* Easier Version: without AWAIT. Apt and Olderog. page 256: *}
lemma Zero_Search_2:
"\<lbrakk>I1=\<guillemotleft> a\<le>\<acute>x \<and> (\<acute>found \<longrightarrow> (a<\<acute>x \<and> f(\<acute>x)=0) \<or> (\<acute>y\<le>a \<and> f(\<acute>y)=0))
\<and> (\<not>\<acute>found \<and> a<\<acute>x \<longrightarrow> f(\<acute>x)\<noteq>0)\<guillemotright>;
I2= \<guillemotleft>\<acute>y\<le>a+1 \<and> (\<acute>found \<longrightarrow> (a<\<acute>x \<and> f(\<acute>x)=0) \<or> (\<acute>y\<le>a \<and> f(\<acute>y)=0))
\<and> (\<not>\<acute>found \<and> \<acute>y\<le>a \<longrightarrow> f(\<acute>y)\<noteq>0)\<guillemotright>\<rbrakk> \<Longrightarrow>
\<parallel>- .{\<exists>u. f(u)=0}.
\<acute>found:= False,,
\<acute>x:=a,, \<acute>y:=a+1,,
COBEGIN .{\<acute>I1}.
WHILE \<not>\<acute>found
INV .{\<acute>I1}.
DO .{a\<le>\<acute>x \<and> (\<acute>found \<longrightarrow> \<acute>y\<le>a \<and> f(\<acute>y)=0) \<and> (a<\<acute>x \<longrightarrow> f(\<acute>x)\<noteq>0)}.
\<langle> \<acute>x:=\<acute>x+1,,IF f(\<acute>x)=0 THEN \<acute>found:=True ELSE SKIP FI\<rangle>
OD
.{\<acute>I1 \<and> \<acute>found}.
\<parallel>
.{\<acute>I2}.
WHILE \<not>\<acute>found
INV .{\<acute>I2}.
DO .{\<acute>y\<le>a+1 \<and> (\<acute>found \<longrightarrow> a<\<acute>x \<and> f(\<acute>x)=0) \<and> (\<acute>y\<le>a \<longrightarrow> f(\<acute>y)\<noteq>0)}.
\<langle> \<acute>y:=(\<acute>y - 1),,IF f(\<acute>y)=0 THEN \<acute>found:=True ELSE SKIP FI\<rangle>
OD
.{\<acute>I2 \<and> \<acute>found}.
COEND
.{f(\<acute>x)=0 \<or> f(\<acute>y)=0}."
apply oghoare
--{* 20 vc *}
apply auto
--{* auto takes aprox. 2 minutes. *}
done
subsection {* Producer/Consumer *}
subsubsection {* Previous lemmas *}
lemma nat_lemma2: "\<lbrakk> b = m*(n::nat) + t; a = s*n + u; t=u; b-a < n \<rbrakk> \<Longrightarrow> m \<le> s"
proof -
assume "b = m*(n::nat) + t" "a = s*n + u" "t=u"
hence "(m - s) * n = b - a" by (simp add: diff_mult_distrib)
also assume "\<dots> < n"
finally have "m - s < 1" by simp
thus ?thesis by arith
qed
lemma mod_lemma: "\<lbrakk> (c::nat) \<le> a; a < b; b - c < n \<rbrakk> \<Longrightarrow> b mod n \<noteq> a mod n"
apply(subgoal_tac "b=b div n*n + b mod n" )
prefer 2 apply (simp add: mod_div_equality [symmetric])
apply(subgoal_tac "a=a div n*n + a mod n")
prefer 2
apply(simp add: mod_div_equality [symmetric])
apply(subgoal_tac "b - a \<le> b - c")
prefer 2 apply arith
apply(drule le_less_trans)
back
apply assumption
apply(frule less_not_refl2)
apply(drule less_imp_le)
apply (drule_tac m = "a" and k = n in div_le_mono)
apply(safe)
apply(frule_tac b = "b" and a = "a" and n = "n" in nat_lemma2, assumption, assumption)
apply assumption
apply(drule order_antisym, assumption)
apply(rotate_tac -3)
apply(simp)
done
subsubsection {* Producer/Consumer Algorithm *}
record Producer_consumer =
ins :: nat
outs :: nat
li :: nat
lj :: nat
vx :: nat
vy :: nat
buffer :: "nat list"
b :: "nat list"
text {* The whole proof takes aprox. 4 minutes. *}
lemma Producer_consumer:
"\<lbrakk>INIT= \<guillemotleft>0<length a \<and> 0<length \<acute>buffer \<and> length \<acute>b=length a\<guillemotright> ;
I= \<guillemotleft>(\<forall>k<\<acute>ins. \<acute>outs\<le>k \<longrightarrow> (a ! k) = \<acute>buffer ! (k mod (length \<acute>buffer))) \<and>
\<acute>outs\<le>\<acute>ins \<and> \<acute>ins-\<acute>outs\<le>length \<acute>buffer\<guillemotright> ;
I1= \<guillemotleft>\<acute>I \<and> \<acute>li\<le>length a\<guillemotright> ;
p1= \<guillemotleft>\<acute>I1 \<and> \<acute>li=\<acute>ins\<guillemotright> ;
I2 = \<guillemotleft>\<acute>I \<and> (\<forall>k<\<acute>lj. (a ! k)=(\<acute>b ! k)) \<and> \<acute>lj\<le>length a\<guillemotright> ;
p2 = \<guillemotleft>\<acute>I2 \<and> \<acute>lj=\<acute>outs\<guillemotright> \<rbrakk> \<Longrightarrow>
\<parallel>- .{\<acute>INIT}.
\<acute>ins:=0,, \<acute>outs:=0,, \<acute>li:=0,, \<acute>lj:=0,,
COBEGIN .{\<acute>p1 \<and> \<acute>INIT}.
WHILE \<acute>li <length a
INV .{\<acute>p1 \<and> \<acute>INIT}.
DO .{\<acute>p1 \<and> \<acute>INIT \<and> \<acute>li<length a}.
\<acute>vx:= (a ! \<acute>li);;
.{\<acute>p1 \<and> \<acute>INIT \<and> \<acute>li<length a \<and> \<acute>vx=(a ! \<acute>li)}.
WAIT \<acute>ins-\<acute>outs < length \<acute>buffer END;;
.{\<acute>p1 \<and> \<acute>INIT \<and> \<acute>li<length a \<and> \<acute>vx=(a ! \<acute>li)
\<and> \<acute>ins-\<acute>outs < length \<acute>buffer}.
\<acute>buffer:=(list_update \<acute>buffer (\<acute>ins mod (length \<acute>buffer)) \<acute>vx);;
.{\<acute>p1 \<and> \<acute>INIT \<and> \<acute>li<length a
\<and> (a ! \<acute>li)=(\<acute>buffer ! (\<acute>ins mod (length \<acute>buffer)))
\<and> \<acute>ins-\<acute>outs <length \<acute>buffer}.
\<acute>ins:=\<acute>ins+1;;
.{\<acute>I1 \<and> \<acute>INIT \<and> (\<acute>li+1)=\<acute>ins \<and> \<acute>li<length a}.
\<acute>li:=\<acute>li+1
OD
.{\<acute>p1 \<and> \<acute>INIT \<and> \<acute>li=length a}.
\<parallel>
.{\<acute>p2 \<and> \<acute>INIT}.
WHILE \<acute>lj < length a
INV .{\<acute>p2 \<and> \<acute>INIT}.
DO .{\<acute>p2 \<and> \<acute>lj<length a \<and> \<acute>INIT}.
WAIT \<acute>outs<\<acute>ins END;;
.{\<acute>p2 \<and> \<acute>lj<length a \<and> \<acute>outs<\<acute>ins \<and> \<acute>INIT}.
\<acute>vy:=(\<acute>buffer ! (\<acute>outs mod (length \<acute>buffer)));;
.{\<acute>p2 \<and> \<acute>lj<length a \<and> \<acute>outs<\<acute>ins \<and> \<acute>vy=(a ! \<acute>lj) \<and> \<acute>INIT}.
\<acute>outs:=\<acute>outs+1;;
.{\<acute>I2 \<and> (\<acute>lj+1)=\<acute>outs \<and> \<acute>lj<length a \<and> \<acute>vy=(a ! \<acute>lj) \<and> \<acute>INIT}.
\<acute>b:=(list_update \<acute>b \<acute>lj \<acute>vy);;
.{\<acute>I2 \<and> (\<acute>lj+1)=\<acute>outs \<and> \<acute>lj<length a \<and> (a ! \<acute>lj)=(\<acute>b ! \<acute>lj) \<and> \<acute>INIT}.
\<acute>lj:=\<acute>lj+1
OD
.{\<acute>p2 \<and> \<acute>lj=length a \<and> \<acute>INIT}.
COEND
.{ \<forall>k<length a. (a ! k)=(\<acute>b ! k)}."
apply oghoare
--{* 138 vc *}
apply(tactic {* ALLGOALS Clarify_tac *})
--{* 112 subgoals left *}
apply(simp_all (no_asm))
apply(tactic {*ALLGOALS (conjI_Tac (K all_tac)) *})
--{* 930 subgoals left *}
apply(tactic {* ALLGOALS Clarify_tac *})
apply(simp_all (asm_lr) only:length_0_conv [THEN sym])
--{* 44 subgoals left *}
apply (simp_all (asm_lr) del:length_0_conv add: nth_list_update mod_less_divisor mod_lemma)
--{* 32 subgoals left *}
apply(tactic {* ALLGOALS Clarify_tac *})
apply(tactic {* TRYALL simple_arith_tac *})
--{* 9 subgoals left *}
apply (force simp add:less_Suc_eq)
apply(drule sym)
apply (force simp add:less_Suc_eq)+
done
subsection {* Parameterized Examples *}
subsubsection {* Set Elements of an Array to Zero *}
record Example1 =
a :: "nat \<Rightarrow> nat"
lemma Example1:
"\<parallel>- .{True}.
COBEGIN SCHEME [0\<le>i<n] .{True}. \<acute>a:=\<acute>a (i:=0) .{\<acute>a i=0}. COEND
.{\<forall>i < n. \<acute>a i = 0}."
apply oghoare
apply simp_all
done
text {* Same example with lists as auxiliary variables. *}
record Example1_list =
A :: "nat list"
lemma Example1_list:
"\<parallel>- .{n < length \<acute>A}.
COBEGIN
SCHEME [0\<le>i<n] .{n < length \<acute>A}. \<acute>A:=\<acute>A[i:=0] .{\<acute>A!i=0}.
COEND
.{\<forall>i < n. \<acute>A!i = 0}."
apply oghoare
apply force+
done
subsubsection {* Increment a Variable in Parallel *}
text {* First some lemmas about summation properties. *}
(*
lemma Example2_lemma1: "!!b. j<n \<Longrightarrow> (\<Sum>i::nat<n. b i) = (0::nat) \<Longrightarrow> b j = 0 "
apply(induct n)
apply simp_all
apply(force simp add: less_Suc_eq)
done
*)
lemma Example2_lemma2_aux: "!!b. j<n \<Longrightarrow>
(\<Sum>i=0..<n. (b i::nat)) =
(\<Sum>i=0..<j. b i) + b j + (\<Sum>i=0..<n-(Suc j) . b (Suc j + i))"
apply(induct n)
apply simp_all
apply(simp add:less_Suc_eq)
apply(auto)
apply(subgoal_tac "n - j = Suc(n- Suc j)")
apply simp
apply arith
done
lemma Example2_lemma2_aux2:
"!!b. j\<le> s \<Longrightarrow> (\<Sum>i::nat=0..<j. (b (s:=t)) i) = (\<Sum>i=0..<j. b i)"
apply(induct j)
apply (simp_all cong:setsum_cong)
done
lemma Example2_lemma2:
"!!b. \<lbrakk>j<n; b j=0\<rbrakk> \<Longrightarrow> Suc (\<Sum>i::nat=0..<n. b i)=(\<Sum>i=0..<n. (b (j := Suc 0)) i)"
apply(frule_tac b="(b (j:=(Suc 0)))" in Example2_lemma2_aux)
apply(erule_tac t="setsum (b(j := (Suc 0))) {0..<n}" in ssubst)
apply(frule_tac b=b in Example2_lemma2_aux)
apply(erule_tac t="setsum b {0..<n}" in ssubst)
apply(subgoal_tac "Suc (setsum b {0..<j} + b j + (\<Sum>i=0..<n - Suc j. b (Suc j + i)))=(setsum b {0..<j} + Suc (b j) + (\<Sum>i=0..<n - Suc j. b (Suc j + i)))")
apply(rotate_tac -1)
apply(erule ssubst)
apply(subgoal_tac "j\<le>j")
apply(drule_tac b="b" and t="(Suc 0)" in Example2_lemma2_aux2)
apply(rotate_tac -1)
apply(erule ssubst)
apply simp_all
done
record Example2 =
c :: "nat \<Rightarrow> nat"
x :: nat
lemma Example_2: "0<n \<Longrightarrow>
\<parallel>- .{\<acute>x=0 \<and> (\<Sum>i=0..<n. \<acute>c i)=0}.
COBEGIN
SCHEME [0\<le>i<n]
.{\<acute>x=(\<Sum>i=0..<n. \<acute>c i) \<and> \<acute>c i=0}.
\<langle> \<acute>x:=\<acute>x+(Suc 0),, \<acute>c:=\<acute>c (i:=(Suc 0)) \<rangle>
.{\<acute>x=(\<Sum>i=0..<n. \<acute>c i) \<and> \<acute>c i=(Suc 0)}.
COEND
.{\<acute>x=n}."
apply oghoare
apply (simp_all cong del: strong_setsum_cong)
apply (tactic {* ALLGOALS Clarify_tac *})
apply (simp_all cong del: strong_setsum_cong)
apply(erule (1) Example2_lemma2)
apply(erule (1) Example2_lemma2)
apply(erule (1) Example2_lemma2)
apply(simp)
done
end