FORTRAN90比較實值

Question

我有以下子程序：

SUBROUTINE matprod(nkval, matrix, tkval, field) 
implicit none 

integer, allocatable, intent(in) :: matrix(:,:,:) 
real, allocatable, intent(inout) :: tkval(:,:,:) 
real, allocatable, intent(in) :: nkval(:,:) 
integer, intent(in) ::field 
integer :: temp, i, j 

allocate(tkval(field,size(matrix,dim=1),3)) 
temp=size(matrix,dim=1) 

do i=1,field 
    do j=1,temp 
    tkval(i,j,:)=matmul(matrix(j,:,:),nkval(:,i)) 
    if (tkval(i,j,1).eq.-0.5) then 
     tkval(i,j,1)=0.5 
    endif 
    if (tkval(i,j,2).eq.-0.5) then 
     tkval(i,j,2)=0.5 
    endif 
    if (tkval(i,j,3).eq.-0.5) then 
     tkval(i,j,3)=0.5 
    endif 
    enddo 
enddo 

END SUBROUTINE matprod 

凡AFER矩陣乘法我有一組三維點，這是我知道的一個事實包含「-0.5」和我想抓住那些和把它們變成正值0.5。出於某種原因，我的if語句沒有看到這些。爲什麼？

這裏是「tkval」與J計數器的輸出樣本顯示：

1 
    0.2500000  0.7499999  0.7499999 
     2 
    0.2500000  0.7499999  0.7499999 
     3 
    0.7499999  0.2500000  0.7499999 
     4 
    0.7499999  0.7499999  0.2500000 
     5 
    0.7499999  0.2500000  0.7499999 
     6 
    0.7499999  0.7499999  0.2500000 
     7 
-0.5000000  0.0000000  -0.7499999 
     8 
-0.5000000  -0.7499999  0.0000000 
     9 
    0.0000000  -0.5000000  -0.7499999 
     10 
    0.0000000  -0.7499999  -0.5000000 
     11 
-0.5000000  0.0000000  -0.7499999 
     12 
-0.5000000  -0.7499999  0.0000000 
     13 
    0.5000000  0.5000000  -0.2500000 
     14 
    0.5000000  -0.2500000  0.5000000 
     15 
    0.0000000  -0.5000000  -0.7499999 
     16 
    0.0000000  -0.7499999  -0.5000000 
     17 
    0.5000000  0.5000000  -0.2500000 
     18 
    0.5000000  -0.2500000  0.5000000 

Answer 1

所以這是我想到的解決我的問題的一種方法：

if ((tkval(i,j,1).lt.-0.49999).and.(tkval(i,j,1).gt.-0.50001)) then 
     tkval(i,j,1)=tkval(i,j,1)*(-1) 
    endif 
    if ((tkval(i,j,2).lt.-0.49999).and.(tkval(i,j,2).gt.-0.50001)) then 
     tkval(i,j,2)=tkval(i,j,2)*(-1) 
    endif 
    if ((tkval(i,j,3).lt.-0.49999).and.(tkval(i,j,3).gt.-0.50001)) then 
     tkval(i,j,3)=tkval(i,j,3)*(-1)