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Ingy döt Net 2015-02-20 00:35:01 -05:00
parent a25938f123
commit 00a190b0a6
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39
Task/Monte-Carlo-methods/REXX/monte-carlo-methods.rexx
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@ -1,36 +1,33 @@
/*REXX program uses the Monte Carlo method to compute pi÷4 */
/*REXX program computes pi÷4 using the Monte Carlo algorithm. */
parse arg times chunks . /*does user want a specific num? */
if times=='' then times=1000000000 /*one billion should do it. */
if chunks=='' then chunks=10000 /*do Monte Carle in 10k chunks. */
if times=='' then times=1000000000 /*one billion should do it. */
if chunks=='' then chunks=10000 /*do Monte Carlo in 10k chunks. */
limit=10000-1 /*REXX random gens only integers.*/
limitSq=limit**2 /*...so, instead of 1, use lim**2*/
limitSq=limit**2 /*···so, instead of 1, use lim**2*/
!=0 /*number of "pi hits" so far. */
accur=0 /*accuracy of the Monte Carlo pi.*/
if 1=='f1'x then piChar='pi' /*if EBCDIC, then use literal. */
else piChar='e3'x /*if ASCII, then use symbol. */
if 1=='f1'x then piChar='pi' /*if EBCDIC, then use literal. */
else piChar='e3'x /*if ASCII, then use pi symbol.*/
pi=3.14159265358979323846264338327950288419716939937511 /*da real McCoy*/
numeric digits length(pi) /*at least, we'll use these digs.*/
say 'real pi='pi"+" /*might was well brag about it. */
say /*just for the eyeballs. */
do j=1 for times%chunks
do chunks /*do Monte Carlo, chunk-at-a-time*/
if random(0,limit)**2+random(0,limit)**2<=limitSq then !=!+1
end
do j=1 for times%chunks
do chunks /*do Monte Carlo, chunk-at-a-time*/
if random(0,limit)**2 + random(0,limit)**2 <=limitSq then !=!+1
end /*chunks*/
reps=chunks*j /*compute number of repetitions. */
piX=4*!/reps /*let's see how this puppy does. */
_=compare(piX,pi) /*compare apples & ...crabapples.*/
if _<=accur then iterate /*if not better accuracy, pout. */
_=compare(piX,pi) /*compare apples & ···crabapples.*/
if _<=accur then iterate /*if not better accuracy, pout. */
say right(comma(reps),20) 'repetitions: Monte Carlo' piChar,
"is accurate to" _-1 'places.' /*subtract 1 for dec point.*/
accur=_ /*use this accuracy for baseline.*/
end /*j*/
end /*j*/
exit /*stick a fork in it, we're done.*/
/*────────────────────────────────COMMA subroutine──────────────────────*/
comma: procedure; parse arg _,c,p,t; arg ,cu; c=word(c ",",1)
if cu=='BLANK' then c=' '; o=word(p 3,1); p=abs(o); t=word(t 999999999,1)
if \datatype(p,'W') | \datatype(t,'W')|p==0|arg()>4 then return _; n=_'.9'
#=123456789; k=0; if o<0 then do; b=verify(_,' '); if b==0 then return _
e=length(_) - verify(reverse(_),' ') + 1; end; else do; b=verify(n,#,"M")
e=verify(n,#'0',,verify(n,#"0.",'M'))-p-1; end
do j=e to b by -p while k<t; _=insert(c,_,j); k=k+1; end; return _
/*────────────────────────────────COMMA subroutine────────────────────────────────────────────────────────────────────────────────────*/
comma: procedure; parse arg _,c,p,t; arg ,cu; c=word(c ",",1); if cu=='BLANK' then c=' '; o=word(p 3,1); p=abs(o); t=word(t 999999999,1)
if \datatype(p,'W') | \datatype(t,'W') | p==0 | arg()>4 then return _; n=_'.9'; #=123456789; k=0; if o<0 then do; b=verify(_,' ')
if b==0 then return _; e=length(_) - verify(reverse(_),' ') + 1; end; else do;
b=verify(n,#,"M"); e=verify(n,#'0',,verify(n,#"0.",'M'))-p-1; end; do j=e to b by -p while k<t; _=insert(c,_,j); k=k+1; end; return _