Hm, there is a problem with my program, because 9387361 is the proper answer to this question.  It holds true for all conditions. ... View more

I have to send a kudos to SASJedi as well for going well beyond in his response what I would consider necessary and giving you not just an answer to point you in a direction but a real process to utilize. ... View more

Yes, the function is not incredibly effiecient.  The macro I posted earlier will implement a type of sieve process, but also not in a very effiecent way. The goal is to find a single prime that meets the 4 rules listed. For example my program will fairly quickly find the answer to meet the last two rules: Find the smallest number that can be expressed as the sum of 405 consecutive prime numbers, the sum of 781 consecutive prime numbers, and is itself a prime number. SOLUTION FOUND: 9387361 in about 20 seconds.  I'd consider this fairly acceptable.  However this number does not appear to work for the next two rules: the sum of 19 consecutive prime numbers, the sum of 21 consecutive prime numbers, The process I have is just not efficient to the degree in needs to be to solve this reasonably, even though, given time, it could probably get there... The main issue with the performance of this method is the checking of the sum's to be prime, because these are very large numbers eventually and the method I am using scales very poorly as the size of the integer to check increases. %macro primesums(seq1 ,seq2); proc fcmp outlib=work.func.cipher; function isprime(num);   n=0;   j=3;   do while(j<=int(sqrt(num)) and n=0);    if mod(num,j)=0 then n+1;    j+2;   end;   if n=0 then return(1);   else return(0); endsub; run; %let cmplib=%sysfunc(getoption(cmplib)); options cmplib=(work.func &cmplib); data primes; pnum=2; i=1; output; i=2; output; do i=3 to int(10**4.5) by 2;   if isprime(i) then    do;     pnum+1;     output;    end; end; call symput('nobs',pnum); keep i; run; sasfile work.primes load; %do i=1 %to 2; %let j=%eval(&i-1); data _null_; found=0; obsnum=1; cnt=1; iter=1; length ptots $32000; retain ptots '0'; do until(obsnum+&&seq&i>&nobs %if &i>1 %then %do; or found>0 %end;);   set primes point=obsnum;   ptot+i;   if cnt eq &&seq&i and %if &i=1 %then %do; isprime(ptot) %end; %else %do; ptot in (&&ptot&j) %end; then    do;     found+1;     %if &i>1 %then %do; put 'SOLUTION FOUND: ' ptot; %end;     ptots=catx(',', of ptots ptot);    end;   else if cnt gt &&seq&i then    do;     iter+1;     cnt=1;     obsnum=iter;     %if &i>1 %then %do;     if ptot>max(&&ptot&j) then      do;       put 'ERROR: Solution not found ' ptot= " is greater than %sysfunc(max(&&ptot&j))";       stop;      end;     %end;     ptot=0;    end;   else    do;     obsnum+1;     cnt+1;    end; end; put found=; call symput("ptot&i",ptots); stop; run; %end; sasfile work.primes close; options cmplib=(&cmplib); %mend; %primesums(781,405) ... View more

Excellent work Art, very impressive!  Wish I had a little more time to have dedicate to this one. ... View more

I have yet to let this run long enough to solve the problem, since I am not happy with it's efficiency, however, I am somewhat confident that given enough time it would solve the question.  The first loop to calculate the prime numbers that are the sum of 781 other consecutive primes with run for a substantial amount of time.  On my machine I let it will run for about 40 minutes, which I do not like. %macro primesums(seq1 ,seq2 ,seq3 ,seq4); proc fcmp outlib=work.func.cipher; function isprime(num);   n=0;   j=3;   do while(j<=int(sqrt(num)) and n=0);    if mod(num,j)=0 then n+1;    j+2;   end;   if n=0 then return(1);   else return(0); endsub; run; %let cmplib=%sysfunc(getoption(cmplib)); options cmplib=(work.func &cmplib); data primes; pnum=2; i=1; output; i=2; output; do i=3 to 10**7 by 2;   if isprime(i) then    do;     pnum+1;     output;    end; end; call symput('nobs',pnum); keep i; run; sasfile work.primes load; %do i=1 %to 4; %let j=%eval(&i-1); data _null_; found=0; obsnum=1; cnt=1; iter=1; length ptots $32000; retain ptots '0'; do until(obsnum+&&seq&i>&nobs %if &i=4 %then %do; or found>0 %end;);   set primes point=obsnum;   ptot+i;   if cnt eq &&seq&i and isprime(ptot) then    do;     found+1;     %if &i>1 %then %do; put 'SOLUTION FOUND: ' ptot; %end;     ptots=catx(',', of ptots ptot);    end;   else if cnt gt &&seq&i then    do;     iter+1;     cnt=1;     obsnum=iter;     %if &i>1 %then %do;     if ptot>max(&&ptot&j) then      do;       put 'ERROR: Solution not found ' ptot= " is greater than %sysfunc(max(&&ptot&j))";       stop;      end;     %end;     ptot=0;    end;   else    do;     obsnum+1;     cnt+1;    end; end; put found=; call symput("ptot&i",ptots); stop; run; %end; sasfile work.primes close; options cmplib=(&cmplib); %mend; %primesums(781,450,21,19) ... View more

Nicely done Tom, thanks. ... View more

Yes it is a common issue, you can read about it more it is commonly referred to as the NUXI problem, I beleive.  It is because of the particularities of the system running to code and what that systems endianess is. ... View more

Typically in the software used by this site a nice way to implement user managed FAQs is by allowing the posting of documents.  Another option is to have a moderated FAQ section that is not open to public posting but allows a user list to post and moderate content as needed. ... View more

Hi Art, Very good work so far.  Here is a great reference point for your topic: http://support.sas.com/documentation/cdl/en/lrdict/64316/HTML/default/viewer.htm#a001258728.htm ... View more

%macro vnumlist(lib, sds, svar); %global g_vnumsum; proc sql noprint;   select count(*) into :vnobs     from sashelp.vcolumn    where libname="%upcase(&lib)"                and memname="%upcase(&sds)"                      and type='num'; %if &vnobs>0 %then   %do;    select name into :vnames separated by ' '      from sashelp.vcolumn     where libname="%upcase(&lib)"                 and memname="%upcase(&sds)"                       and type='num';    %let g_vnumsum=&svar=sum(of &vnames);   %end; %else   %do;    %let g_vnumsum=%str();    %put WARNING: No Numeric Variables to Sum;   %end; quit; %mend; %vnumlist(sashelp, class, total) data want; set sashelp.class; &g_vnumsum; run; ... View more

No it is not very efficient, in my opinion there are a number of clear and obvious flaws.  That being said, his method uses SAS/IML, which I do not have... Here is a pretty fast version, written in C that I will try later to implement similar functionality via proc proto: http://www.fpx.de/fp/Software/sieve.c #include <stdio.h> #include <malloc.h> #include <time.h> #define TEST(f,x)     (*(f+(x)/16)&(1<<(((x)%16L)/2))) #define SET(f,x)     *(f+(x)/16)|=1<<(((x)%16L)/2) int main(int argc, char *argv[]) {   unsigned char *feld=NULL, *zzz;   unsigned long teste=1, max, mom, hits=1, count, alloc, s=0, e=1;   time_t begin;   if (argc > 1)     max = atol (argv[1]) + 10000;   else     max = 14010000L;   while (feld==NULL)         zzz = feld = malloc (alloc=(((max-=10000L)>>4)+1L));   for (count=0; count<alloc; count++) *zzz++ = 0x00;   printf ("Searching prime numbers to : %ld\n", max);   begin = time (NULL);   while ((teste+=2) < max)         if (!TEST(feld, teste)) {                 if  (++hits%2000L==0) {printf (" %ld. prime number\x0d", hits); fflush(stdout);}                 for (mom=3L*teste; mom<max; mom+=teste<<1) SET (feld, mom);                 }   printf (" %ld prime numbers foundn %ld secs.\n\nShow prime numbers",           hits, time(NULL)-begin);   while (s<e) {         printf ("\n\nStart of Area : "); fflush (stdout); scanf ("%ld", &s);         printf ("End   of Area : ");     fflush (stdout); scanf ("%ld", &e);         count=s-2; if (s%2==0) count++;         while ((count+=2)<e) if (!TEST(feld,count)) printf ("%ld\t", count);         }   free (feld);   return 0; } ... View more

Any luck with creating this file Art?  The issue I am finding is the there are a number of varieties based on manufacturer and exif version, an I do not seem to have a camera or program that allows me to create a subject tag that you describe.  A simple 1x1 pixel image in your desired format and exif version would provide the simpliest file for me to work with. ... View more

Here is a macro to generate prime numbers also. %macro get_primes(from, to); data pnbrs;   %if &from<=2 %then %do; i=2; output; %end;   do i=&from to &to;    if mod(i,2) ne 0 then output;   end; run; sasfile work.pnbrs open; %let nbr=&from; data pnbrs;   modify pnbrs;   if i>&nbr and mod(i,&nbr)=0 then remove; run; %do %while(%eval(&nbr**2)<=%eval(&to));   proc sql noprint;    select min(i) into :nbr from pnbrs where i>&nbr;   quit;   data pnbrs;    modify pnbrs;    if i>&nbr and mod(i,&nbr)=0 then remove;   run; %end; sasfile work.pnbrs close; %mend; %get_primes(2,10**7); ... View more

Hi, I have spent a minute on another method to calculate prime numbers, it could gain effeciency by have a better method to reduce loops for higher numbers.  You could write a method in C using proc proto, I have begun on something. data test;   i=2; output; i=3; output; i=5; do while(i<10**7);   n=0;   j=3;   do while(j<=int(sqrt(i)) and n=0);    if mod(i,j)=0 then n+1;   j+2;   end;   if n=0 then output;   i+2; end; run; I avoid even numbers because the only even prime number is 2 and the products of even numbers are also even so I avoid testing even numbers as factors.  With the code above I find 664,579 prime numbers in a little under a minute on a server with load.  I confirm output set against the dataset from website discussed here and have 100% match.  As the number of tests increases the time per test increases logaritmically.  Better logic for reducing the number of factors to test would dramatically improve performance for testing to more prime numbers. ... View more

After further reading this method is only valid for the first 15 prime numbers   The formula breaks down on the 16th iteration (a(16)=49). ... View more