Twin primes: Difference between revisions
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→{{header|Wren}}: Minor tidy
(New post without using any external libraries, in addition to an existing post which uses the "primesieve.hpp" external library.) |
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Under 1,000,000,000 there are 3,424,506 pairs of twin primes.
</pre>
=={{header|EasyLang}}==
{{trans|AWK}}
<syntaxhighlight lang=easylang>
fastfunc isprim num .
if num mod 2 = 0 and num > 2
return 0
.
i = 3
while i <= sqrt num
if num mod i = 0
return 0
.
i += 2
.
return 1
.
func count limit .
p2 = 1
p3 = 1
for i = 5 to limit
p3 = p2
p2 = p1
p1 = isprim i
if p3 = 1 and p1 = 1
cnt += 1
.
.
return cnt
.
n = 1
for i = 1 to 6
n *= 10
print "twin prime pairs < " & n & " : " & count n
.
</syntaxhighlight>
=={{header|F Sharp|F#}}==
Line 1,044 ⟶ 1,080:
=={{header|J}}==
<syntaxhighlight lang="j">tp=:
NB. i.&.(p:inv) generate a list of primes below the given limit
NB.
NB. _2 +/@:= compare these differences to -2, and
NB. sum up the resulting boolean list (get the number of twin pairs)</syntaxhighlight>
{{out}}
<pre> tp
2 8 35 205 1224 8169 58980
NB. test larger limits, and get their time/space usage
tp
440312
timespacex 'tp
0.657576 2.01377e8
tp 1e9
3424506
timespacex 'tp 1e9'
8.59713 1.61071e9
</pre>
=={{header|jq}}==
Line 1,339 ⟶ 1,372:
The time complexity here is all about building a table of primes. It turns out that using the builtin get_prime() is actually faster
than using an explicit sieve (as per Delphi/Go/Wren) due to retaining all the intermediate 0s, not that I particularly expect this to win any performance trophies.
<!--
<syntaxhighlight lang="phix">
with javascript_semantics
atom t0 = time()
function twin_primes(integer maxp, bool both=true)
integer n = 0, -- result
pn = 2, -- next prime index
p, -- a prime, <= maxp
prev_p = 2
while true do
p = get_prime(pn)
if both and p>=maxp then exit end if
n += (prev_p = p-2)
if (not both) and p>=maxp then exit end if
prev_p = p
pn += 1
end while
return n
end function
integer mp = 6 -- prompt_number("Enter limit:")
printf(1,"Twin prime pairs less than %,d: %,d\n",{mp,twin_primes(mp)})
printf(1,"Twin prime pairs less than %,d: %,d\n",{mp,twin_primes(mp,false)})
for p=1 to 9 do
integer p10 = power(10,p)
printf(1,"Twin prime pairs less than %,d: %,d\n",{p10,twin_primes(p10)})
end for
?elapsed(time()-t0)
</syntaxhighlight>
{{out}}
<pre>
Line 1,381 ⟶ 1,415:
"16.2s"
</pre>
=== using primesieve ===
Windows 64-bit only, unless you can find/make a suitable dll/so.<br>
Note that unlike the above this version of twin_primes() carries on from where it left off.
<syntaxhighlight lang="phix">
requires(WINDOWS)
requires(64,true)
include builtins/primesieve.e
atom t0 = time()
integer n = 0, p = 2, prev_p = 2
function twin_primes(integer maxp, bool both=true)
while true do
if both and p>=maxp then exit end if
n += (prev_p = p-2)
if (not both) and p>=maxp then exit end if
prev_p = p
p = primesieve_next_prime()
end while
return n
end function
for i=1 to 11 do
integer p10 = power(10,i)
printf(1,"Twin prime pairs less than %,d: %,d\n",{p10,twin_primes(p10)})
end for
?elapsed(time()-t0)
</syntaxhighlight>
{{out}}
Same as above, which it completes in 7.2s (and 1e10 in 1 min 6s), less the 6's and plus two more lines:
<pre>
Twin prime pairs less than 10: 2
Twin prime pairs less than 100: 8
Twin prime pairs less than 1,000: 35
Twin prime pairs less than 10,000: 205
Twin prime pairs less than 100,000: 1,224
Twin prime pairs less than 1,000,000: 8,169
Twin prime pairs less than 10,000,000: 58,980
Twin prime pairs less than 100,000,000: 440,312
Twin prime pairs less than 1,000,000,000: 3,424,506
Twin prime pairs less than 10,000,000,000: 27,412,679
Twin prime pairs less than 100,000,000,000: 224,376,048
"10 minutes and 25s"
</pre>
=={{header|PureBasic}}==
Line 1,528 ⟶ 1,602:
my $p = Math::Primesieve.new;
printf "Twin prime pairs less than %
say (now - INIT now).round(.01) ~ ' seconds';</syntaxhighlight>
{{out}}
<pre>Twin prime pairs less than 10: 2
Twin prime pairs less than 100: 8
Twin prime pairs less than 1,000: 35
Twin prime pairs less than 10,000: 205
Twin prime pairs less than 100,000: 1,224
Twin prime pairs less than 1,000,000: 8,169
Twin prime pairs less than 10,000,000: 58,980
Twin prime pairs less than 100,000,000: 440,312
Twin prime pairs less than 1,000,000,000: 3,424,506
Twin prime pairs less than 10,000,000,000: 27,412,679
Twin prime pairs less than 100,000,000,000: 224,376,048
Twin prime pairs less than 1,000,000,000,000: 1,870,585,220
6.89 seconds</pre>
=={{header|REXX}}==
Line 1,877 ⟶ 1,955:
{{libheader|Wren-math}}
{{libheader|Wren-fmt}}
<syntaxhighlight lang="
import "./fmt" for Fmt
var c = Int.primeSieve(1e8-1, false)
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