Simple reading function
I guess this is something stupid that I missed, but I asked my whole class and no one can figure it out. Making a simple program that calls in a subroutine and I'm having trouble reading the do loop in matrix entries.
program Householder_Program
use QR_Factorisation
use numeric_kinds
complex(dp), dimension(:,:), allocatable :: A, Q, R, V
integer :: i, j, n, m
print *, 'Enter how many rows in the matrix A'
read *, m
print *, 'Enter how many columns in the matrix A'
read *, n
allocate(A(m,n), Q(m,n), R(n,n), V(n,n))
do i = 1,m
do j = 1,n
Print *, 'Enter row', i, 'and column', j, 'of matrix A'
read *, A(i,j)
end do
end do
call Householder_Triangularization(A,V,R,n,m)
print *, R
end program
It will ask me for A (1,1), but when I dial the number, it will not ask me for A (1,2), it will leave a blank line. When I try to enter the second number it will fail and say:
Enter row 1 and column 1 of matrix A
1
2
At line 22 of file HouseholderProgram.f90 (unit = 5, file = 'stdin')
Fortran runtime error: Bad repeat count in item 1 of list input
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Your variable A
is (array) of type complex. This means that when you try to enter values with a list of item values, you cannot just specify a single number. So, in your case, the problem is not with the program, but with the input.
From Fortran 2008 standard, 10.10.3
When the next effective element is of complex type, the input form consists of a left parenthesis followed by an ordered pair of numeric input fields, separated by commas (if decimal editing mode is POINT) or semicolons (if decimal rule mode is COMMA), followed by a right parenthesis ...
Input, then, should be something like (1., 12.)
.
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If the user input is always large and you want to read it into an array of complex types, you can do something like this:
Print *, 'Enter row', i, 'and column', j, 'of matrix A'
read *, dummy
A(i,j)=dummy
where dummy
declared real
. This saves the user from having to insert the parentheses required for complex numbers. (Conversion to complex is done automatically)
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