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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: – ͖ – shape ȋȀ͖ǡ͘ /) - ͖͘ - size ͜ Declaring an Array For example, suppose we have the following array declarations: REAL, DIMENSION(-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 REALs and the indices are in the range of -1 and 1. The elements of array InputData are INTEGERs and the indices are 100. Both x, and y have 8 elements. ϭ declares an array which has 25 elements with each element having a character string of size 10. The integers in an extent can be PARAMETERs: INTEGER, PARAMETER ::x = 5 INTEGER, PARAMETER :: y = 10 REAL, DIMENSION(x,y) :: Score, Mark Array Input/Output 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 Initializing arrays This is to be used for 1-dimensional arrays that need to be assigned with various values INTEGER :: a(6)=(/1,2,3,6,7,8/) Ϯ DATA statement 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/ Arrays Operations For example, if a and b are both 2x3 arrays the result of addition is and of multiplication is 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)) WRITEˬ WRITE(*,3) ((D(i,J),J=1,3),I=1,2 WRITEˬ 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 Example Find the larger element of the corresponding elements of two arrays and store it into a third one PROGRAM XX IMPLICIT NONE integer, PARAMETER:: LENGTH = 5 integer, DIMENSION(1:LENGTH) :: A, B, C INTEGER :: I DATA A/3, 8,29,100,9 DATA B/54,87,24,108,5 DO I = 1, LENGTH IF (A(I) > B(I)) THEN C(I) = A(I) ELSE C(I) = B(I) END IF END DO WRITE(*,3)(C(i),i=1,LENGTH) 3FORMAT(5(2x,I5)) END 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) ϰ 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 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 7 23 35 28 7 13 21 14 10 20 32 22 ϱ ͵ͷ ͵ ቃ Ͷ ʹ