advertisement

FORTRAN 90 Lecturer: Rafel Hekmat Hameed University of Babylon Subject: Fortran 90 College of Engineering Year: Second B.Sc. Mechanical Engineering Dep. ARRAYS Terminology Rank = Number of dimensions Extent = Number of elements in a dimension Shape = Vector of extents Size = Product of extents Conformance = same shape Consider the following array: – rank 2 – shape (/ 2, 4 /) - extents 2 and 4 - size 8 Declariing an A Arrray For example, suppose we have the following array declarations: REAL, DIMENSION(-1:1) 1:1) :: a, Sum INTEGER, DIMENSION(100) :: InputData INTEGER, DIMENSION(8) :: x,y CHARACTER (len=10) :: names(25) The elements of arrays a and Sum are REALss and the indices are in the range of -1 and 1. The elements of array InputData are INTEGERs and the indices ndices are 100. Both x, and y have 8 elements. declares an array which has 25 elements with each element having a character string of size 10. ϭ The integers in an extent can be PARAMETERs: INTEGER, PARAMETER ::x = 5 INTEGER, PARAMETER :: y = 10 REAL, DIMENSION(x,y) :: Score, Mark Array Input/Outputt The easiest way of reading data into an array could be the following: INTEGER, DIMENSION(1:10) :: x INTEGER :: n, i READ(*,*) n DO i = 1, n READ(*,*) x(i) END DO The implied DO can simplify this greatly. Consider the following example: INTEGER, DIMENSION(1:10) :: x INTEGER :: n, i READ(*,*) n READ(*,*) (x(i), i=1, n) INTEGER, DIMENSION(3,5) :: a INTEGER :: I,j READ(*,*) ((a(I,j), j=1, 5),i=1,3) INTEGER, DIMENSION(2:4,0:1) :: a WRITE(*,*) ((a(i,j),j=0,1),i=2,4) INTEGER, DIMENSION(2:4,0:1) :: a DO i = 2, 4 READ(*,*) (a(i,j),j=0,1) END DO DATA stateement Use the DATA when other methods are tedious and/or impossible. For example for more than one array initialization or for array section initialization. INTEGER :: a(4), b(2,2), c(10) DATA a/4,3,2,1/ DATA a/4*0/ DATA b(1,:)/0,0/ DATA b(2,:)/1,1/ DATA (c(i),i=1,10,2)/5*1/ DATA (c(i),i=2,10,2)/5*2/ Ϯ Arrays Operations For example, if a and b are both 2x3 arrays the result of addition is and of multiplication is EXAMPLE Write a program to add, subtract, and multiply to matrices A & B PROGRAM XW IMPLICIT NONE INTEGER, DIMENSION(2,3) :: A, B, C, D, E INTEGER::I,J DATA A/3, 5,4,6,8,6 DATA B/5,3,2,3,1,1 C=A+B D=A-B E=A*B WRITE(*,3) ((c(i,J),J=1,3),I=1,2) 3 FORMAT(3(2x,I5)) WRITE WRITE(*,3) ((D(i,J),J=1,3),I=1,2) WRITE WRITE(*,3) ((E(i,J),J=1,3),I=1,2) END If one of the operands is a scalar, then the scalar is broadcast into an array which is conformable with the other operand. Thus, the result of adding 5 to b is ϯ Arrays Multiplication In the multiplication matrices must be the number of columns in the first matrix equals the number of rows in the second matrix. A(N,L) B(L,M) = C(N,M) A(3,2) B(2,4) = C(3,4) ͳ ͷ ʹ ܣൌ ͵ ͳ൩ ܤൌ ቂ ͳ Ͷ ʹ Program multiplication Implicit none Integer parameter:: n=3, m=4 , L=2 Integer, dimension (n,L)::a Integer, dimension (L,m)::b Integer, dimension (n,m)::c Integer::i,j,k Data a/1,3,4,5,1,2/ Read(*,*) ((b(i,j), j=1,m), i=1, L) Do i=1,n Do j=1,m c(I,j)=0 Do k=1,L c(i,j)=c(i,j)+a(i,k)*b(k,j) Enddo ; enddo ; enddo Write(*,50) ((c(i,j),j=1,m),i=1,n) 50 format (4(2x,i5)) End Run 7 23 35 28 7 13 21 14 10 20 32 22 ϰ ͵ͷ ͵ ቃ Ͷ ʹ