Fortran DO Statements (how many loop times)

In summary, the number of times a DO loop will execute in Fortran depends on the loop parameters set by the programmer, and can be specified using the initial value, final value, and step size for the loop control variables. If these variables are not set correctly, the loop may not execute the desired number of times or result in an infinite loop. While the loop control variables can be modified within the DO loop, it is recommended to avoid doing so to prevent unexpected behavior. Other alternatives to using a DO loop in Fortran include the DO WHILE and DO UNTIL loops, as well as using array operations and built-in functions for iterative operations. These alternatives offer more flexibility and may be more efficient in certain cases.
  • #1
rk2ray
9
0
Hello,

Examining the following DO statements and determining how many times each loop will be executed. Assume that all loop index variables are integers.

(a) DO irange = -32768, 32767
(b) DO j = 100, 1, -10
(c) DO count = 2, 3, 4
(d) DO index = -4, -7

(e) DO i = -10, 10, 10
The loop will take 10 increments and will run 2 times.

Thanks for any help.
 
Last edited:
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  • #2
If you don't try to evaluate at least one or two of the easy statements, you won't get any help on the harder ones.
 

1. How many times will a DO loop in Fortran execute?

The number of times a DO loop will execute depends on the loop parameters specified by the programmer. In Fortran, the DO statement allows for a specified number of iterations based on the values of the loop control variables.

2. How do I set the number of loop times in a Fortran DO statement?

The number of loop times in a Fortran DO statement is set by specifying the initial value, final value, and step size for the loop control variables in the DO statement. The formula for determining the number of iterations is ((final value - initial value) / step size) + 1.

3. What happens if the loop control variables in a Fortran DO statement are not specified correctly?

If the loop control variables are not specified correctly, the DO loop may not execute the desired number of times or may result in an infinite loop. It is important to carefully consider the values and step sizes for the loop control variables to ensure the correct number of iterations.

4. Can I modify the loop control variables within a Fortran DO loop?

Yes, the loop control variables can be modified within the DO loop. However, any changes made to the loop control variables will affect the number of iterations and may result in unexpected behavior. It is recommended to avoid modifying loop control variables within a DO loop.

5. Are there any alternatives to using a DO loop in Fortran?

Yes, there are other looping structures in Fortran such as the DO WHILE and DO UNTIL loops. These loops allow for more flexibility in controlling the number of iterations based on specific conditions. Additionally, Fortran also supports the use of array operations and built-in functions for iterative operations, which may be more efficient in some cases.

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