algorithm - Fortran 算法帮助 - 得到错误的结果

Question

我目前正在研究 Fortran 矩阵计算器。我正在编译程序，它似乎可以正常工作，但我没有收到正确的结果。当我选择加法特征时，我的程序在两个矩阵中接受并将它们加在一起。我的结果似乎是错误的。例如，如果我选择两个大小为 2x2 且列表为 1 的矩阵作为每个条目，我会收到 3、3、3 的加法结果。我不知道算法哪里出了问题。我还没有检查其他算法，因为我试图一次修复一个算法。下面是我的代码

  *START PROGRAM
  PROGRAM MAIN

  *DECLARATIONS
  INTEGER SELECTION, DONE, VALID, J, I, K, M, N
  INTEGER, DIMENSION(10,10):: SUM, A, B

  *INTITIALIZE
  M = 0
  N = 0
  J = 0
  I = 0
  K = 0
  DONE = 1
  VALID = 1

  *LOOP UNTIL USER CHOOSES TO QUIT

  DO WHILE(DONE .GT. 0)

  *DISPLAY MENU UNTIL VALID ENTRY IS ENTERED

  DO WHILE (VALID .GT. 0)
  *PRINT MENU
  PRINT *,'MATRIX CALCULATOR'
  PRINT *,'PLEASE MAKE A SELECTION'
  PRINT *,'1) MATRIX ADDITION'
  PRINT *,'2) MATRIX SUBTRACTION'
  PRINT *,'3) MATRIX MULTIPLICATION'
  PRINT *,'4) MATRIX TRANSPOSE'
  PRINT *,'5) QUIT PROGRAM'
  READ (*,*) SELECTION

  *VALID ENTRY CHECK
  IF (SELECTION .GT. 5 .OR. SELECTION .LT. 1) THEN
  PRINT *,'PLEASE ENTER A VALID SELECTION'
  ELSE 
  VALID= -1
  END IF

  *END WHEN VALID ENTRY IS ENTERED
  END DO

  *QUIT?
  IF (SELECTION .EQ. 5) THEN
  DONE = -1
  ELSE
  *OTHERWISE CONTINUE
  *GET DIMENTIONS INPUT 
  PRINT *,'PLEASE ENTER THE DIMENTIONS'
  PRINT *,'ENTER IN M:'
  READ (*,*) M
  PRINT *,'ENTER IN N:'
  READ (*,*) N
  *GET IN MATRIX
  PRINT *, 'PLEASE ENTER IN MATRIX A'
  DO J=1, M
  DO I=1, N
  PRINT *, 'ENTER IN VALUE I, I', J, I
  READ(*,*) A(M,N)
  END DO
  END DO

  PRINT *, 'PLEASE ENTER IN MATRIX B'
  DO J=1, M
  DO I=1, N
  PRINT *, 'ENTER IN VALUE I, I', J,I
  READ(*,*) B(M,N)
  END DO
  END DO

  *PERFORM DESIRED CALCULATION
  SELECT CASE(SELECTION)
  *CASE 1
  CASE (1)
   PRINT *,'MATRIX ADDITION'
   DO J=1,M
   DO I=1,N
   SUM(J,I)=A(J,I)+B(J,I)
   END DO   
   END DO

  *PRINT ADDITION RESULT
   PRINT *,'ADDITION RESULT'
   DO J=1, M
   DO I=1, N
   WRITE (*,*) SUM(J,I)
   END DO
   END DO
  *CASE 2
  CASE (2)
   PRINT *,'MATRIX SUBTRACTION'
   DO J=1,M
   DO I=1,N
   SUM(J,I)=A(J,I)-B(J,I)
   END DO   
   END DO

  *PRINT SUBTRACTION RESULT
   PRINT *,'SUBTRACTION RESULT'
   DO J=1, M
   DO I=1, N
   WRITE (*,*) SUM(J,I)
   END DO
   END DO
  *CASE 3
  CASE (3)
   PRINT *,'MATRIX MULTIPLICATION'
   DO J=1, M
   DO I=1, N
   DO K=1, N
   SUM(J,I) = SUM(J,I)+A(J,K)*B(I,J)
   END DO
   END DO
   END DO

  *PRINT MULTIPLICATION RESULT
   DO J=1, M
   DO I=1, N
   WRITE (*,*) SUM(J,I)
   END DO
   END DO
  *CASE 4
  CASE (4)
   PRINT *,'MATRIX TRANSPOSE'
   DO J=1, M
   DO I=1, N
   B(I,J) = A(J,I)
   END DO
   END DO
  *PRINT TRANSPOSE RESULT
   PRINT *, 'MATRIX A RESULT'
   DO J=1, M
   DO I=1, N
   WRITE (*,*) A(J,I)
   END DO
   END DO
   PRINT *, 'MATRIX B RESULT'
   DO J=1, M
   DO I=1, N
   WRITE (*,*) B(J,I)
   END DO
   END DO
  CASE DEFAULT
   PRINT *,'SOMETHING HAS GONE WRONG'
  END SELECT

  *USER SELECTED TO QUIT
  END IF
  END DO
  PRINT *, 'PROGRAM HAS ENDED'
  *END PROGRAM
  STOP
  END

Answer 1

避免所犯错误的一种方法是使用 Fortran 的数组函数。例如，如果数组 A 和 B 的大小相同，您可以使用单个语句对数组 A 和 B 求和:

C = A + B

您还可以使用内部过程 matmul 和 transpose 分别进行矩阵乘法和转置。