Title: | Mathematics at DEC |
Moderator: | RUSURE::EDP |
Created: | Mon Feb 03 1986 |
Last Modified: | Fri Jun 06 1997 |
Last Successful Update: | Fri Jun 06 1997 |
Number of topics: | 2083 |
Total number of notes: | 14613 |
PROGRAM PRIMEPLOT IMPLICIT INTEGER*4(A-Z) PARAMETER (TOP=40000) LOGICAL*1 PRIMES(TOP) C C Plots primes in a spiral on a VT125. C C Stanley Rabinowitz C C The numbers from 1 to 10000 are drawn in a spiral as follows: C C C 17 16 15 14 13 C 18 5 4 3 12 C 19 6 1 2 11 C 20 7 8 9 10 C 21 22 23 24 25 C C Each prime is displayed as a dot; composite numbers are not displayed. C Interesting unexpected patterns are seen. C BYTE DELTAX(4) /+1, 0,-1, 0/ BYTE DELTAY(4) / 0,+1, 0,-1/ CALL SIEVE(PRIMES,TOP) CALL CLEAR X=0 Y=0 POS=1 NUMBER=1 DO 2 K=1,TOP C C Right k, Up k, Left k+1, Down k+1, etc. C DO 2 JJ=1,2 DO 3 J=1,K IF (NUMBER.EQ.TOP) GOTO 50 NUMBER=NUMBER+1 X=X+DELTAX(POS) Y=Y+DELTAY(POS) IF (PRIMES(NUMBER)) CALL PLOT(X,Y) 3 CONTINUE POS=POS+1 IF (POS.EQ.5) POS=1 2 CONTINUE 50 TYPE 100, 27 100 FORMAT(1X,A1,'\') CALL EXIT END SUBROUTINE SIEVE(PRIMES,TOP) IMPLICIT INTEGER*4(A-Z) LOGICAL*1 PRIMES(TOP) C C Calculate primes to 40,000 using Sieve of Eratosthenes. C For purposes of this program, treat 1 as a prime. C INTEGER*2 PR(7) DATA PR/3,5,7,11,13,17,19/ DO I=2,TOP,2 PRIMES(I-1)=.TRUE. PRIMES(I)=.FALSE. END DO DO 2 I=1,5 P=PR(I) DO 3 J=3*P,TOP,2*P 3 PRIMES(J)=.FALSE. 2 CONTINUE DO 4 I=3,200,2 IF (.NOT.PRIMES(I)) GOTO 4 DO 5 J=3*I,TOP,2*I 5 PRIMES(J)=.FALSE. 4 CONTINUE RETURN END SUBROUTINE CLEAR IMPLICIT INTEGER*4(A-Z) ESC=27 TYPE 100, ESC,ESC,ESC 100 FORMAT(1X,A1,'[H',A1,'[2J',A1,'P1ps(M0(L0)(AL0))S(I0)S(E)S[0,0]') RETURN END SUBROUTINE PLOT(X,Y) IMPLICIT INTEGER*4(A-Z) PARAMETER (XOFFSET=350) PARAMETER (YOFFSET=250) TYPE 100, 2*X+XOFFSET,500-2*Y-YOFFSET 100 FORMAT(' P[',I3,',',I3,']V[]') RETURN END
T.R | Title | User | Personal Name | Date | Lines |
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154.1 | REX::POWERS | Fri Sep 21 1984 14:19 | 11 | ||
The following reply is a SIXEL image of the resulting pattern. It has the proper introducer and terminator sequences to allow it to be TYPEd out after SAVing. The line counter in NOTES-11 turns off SIXEL mode (as I have my terminal line set up, anyway), so the image will not be completely displayed if you just READ it. ADVISORY NOTE: The following reply may cause grief to non-graphics terminal users. It is suggested that you skip the next reply! - tom] | |||||
154.2 | REX::GILBERT | Fri Sep 21 1984 15:24 | 218 | ||
When including a picture (or other fancy graphics), please give a short description and/or warning, followed by a form feed, then the picture. That way, the innocent users have the opportunity to avoid it, and the intended audience can "SAVE TT:" to see it, without first getting stuck in a funny video mode. *** WARNING -- The following contains VT125 graphics *** $[H[2JP1pS(M0(L0)(AL0))S(I0)S(E)S[0,0]\ P1q- - - - !164?S!9?a!5?C!5?A!5?O?a!5?C?G!7?A!5?O!5?_!11?G?C!3?C !5?i?S!3?O!17?_?O!5?A!5?S?G?O!5?A?S!5?_!3?_?O!5?_!7?G?C?_!3? g?O?G?S!9?G?C?A!3?g?S!9?_?C!3?O!5?A!3?G?C?A!3?g!5?O?A!5?C!3? O?_!3?I?O!9?I?O!9?A!3?G?O?_!5?O!5?A!3?_?O?G?C?a!3?A?C!3?C!13 ?a!3?A!5?O?_!3?I!3?G?C!5?_?C?G!7?_?O!9?_!3?G- !152?@!3?O?_!7?G?@?_!3?A?C?G?S!11?S!3?@?A!5?O?A!3?_!5?@?a!3? 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154.3 | HARE::STAN | Mon Sep 24 1984 23:54 | 111 | ||
C C Here's a version where the primes of the form 6k+1 and the primes C of the form 6k-1 are colored with two different colors (red and green). C PROGRAM PRIMEPLOTCOLOR IMPLICIT INTEGER*4(A-Z) PARAMETER (TOP=57600) LOGICAL*1 PRIMES(TOP) C C Plots primes in a spiral on a VT125. C C Stanley Rabinowitz C C The numbers from 1 to 57600 are drawn in a spiral as follows: C C C 17 16 15 14 13 C 18 5 4 3 12 C 19 6 1 2 11 C 20 7 8 9 10 C 21 22 23 24 25 C C Each prime is displayed as a dot; composite numbers are not displayed. C Interesting unexpected patterns are seen. C Primes of the form 6k+1 are colored differently from primes of C the form 6k-1. C BYTE DELTAX(4) /+1, 0,-1, 0/ BYTE DELTAY(4) / 0,+1, 0,-1/ CALL SIEVE(PRIMES,TOP) CALL CLEAR X=0 Y=0 POS=1 NUMBER=1 DO 2 K=1,TOP C C Right k, Up k, Left k+1, Down k+1, etc. C DO 2 JJ=1,2 DO 3 J=1,K IF (NUMBER.EQ.TOP) GOTO 50 NUMBER=NUMBER+1 X=X+DELTAX(POS) Y=Y+DELTAY(POS) IF (PRIMES(NUMBER)) THEN REM=MOD(NUMBER,6) IF (REM.EQ.1) THEN CALL PLOT(X,Y,'R') ELSE CALL PLOT(X,Y,'G') END IF END IF 3 CONTINUE POS=POS+1 IF (POS.EQ.5) POS=1 2 CONTINUE 50 TYPE 100, 27 100 FORMAT(1X,A1,'\') CALL EXIT END SUBROUTINE SIEVE(PRIMES,TOP) IMPLICIT INTEGER*4(A-Z) LOGICAL*1 PRIMES(TOP) C C Calculate primes to 40,000 using Sieve of Eratosthenes. C For purposes of this program, treat 1 as a prime. C INTEGER*2 PR(7) DATA PR/3,5,7,11,13,17,19/ DO I=2,TOP,2 PRIMES(I-1)=.TRUE. PRIMES(I)=.FALSE. END DO DO 2 I=1,7 P=PR(I) DO 3 J=3*P,TOP,2*P 3 PRIMES(J)=.FALSE. 2 CONTINUE DO 4 I=3,300,2 IF (.NOT.PRIMES(I)) GOTO 4 DO 5 J=3*I,TOP,2*I 5 PRIMES(J)=.FALSE. 4 CONTINUE RETURN END SUBROUTINE CLEAR IMPLICIT INTEGER*4(A-Z) ESC=27 TYPE 100, ESC,ESC,ESC 100 FORMAT(1X,A1,'[H',A1,'[2J',A1,'P1ps(M0(L0)(AL0))S(I0)S(E)S[0,0]') RETURN END SUBROUTINE PLOT(X,Y,COLOR) IMPLICIT INTEGER*4(A-Z) PARAMETER (XOFFSET=350) PARAMETER (YOFFSET=240) CHARACTER*1 PREV_COLOR/'X'/ CHARACTER*1 COLOR IF (COLOR.NE.PREV_COLOR) THEN TYPE 101, COLOR 101 FORMAT('+W(I(',A1,$,'))') PREV_COLOR=COLOR END IF TYPE 100, 2*X+XOFFSET,480-2*Y-YOFFSET 100 FORMAT(' P[',I3,',',I3,']V[]') RETURN END | |||||
154.4 | historical background on this | ALLVAX::JROTH | It's a bush recording... | Tue Oct 02 1990 08:38 | 34 |
Path: ryn.esg.dec.com!shlump.nac.dec.com!bacchus.pa.dec.com!decuac!haven!cvl!herve From: [email protected] (Jean-Yves Herve') Newsgroups: sci.math Subject: Re: Pictures of primes in the plane Keywords: Prime numbers Date: 1 Oct 90 22:08:00 GMT References: <[email protected]> Reply-To: [email protected] (Jean-Yves Herve') Organization: Center for Automation Research, Univ. of Md. In article <[email protected]> [email protected] (Cleve Moler) writes: >When we were both graduate students in early '60s, Larry Breed >showed me a fascinating image he had generated that displayed >some interesting properties of prime numbers. Since then, I've ... >Number the points in the plane with integer coordinates in a >"square spiral" pattern as follows: ... >Whose idea was this? > -- Cleve Moler > [email protected] I remember seing this pattern called the Ulam Spiral (as in Stanislaw M. Ulam). Don't know of any reference, though. Jean-Yves. ------------------------------------------------------------------- Jean-Yves Herve' Computer Vision Laboratory [email protected] Center for Automation Research University of Maryland ------------------------------------------------------------------- |