XPost: comp.lang.fortran
[ Crossposting to comp.ai.shells ]
On Thu, 6 Jul 2023 07:34:53 +0200
Giorgio Pastore <
pastgio@units.it> wrote:
Il 06/07/23 04:37, Beliavsky ha scritto:
On Tuesday, April 4, 2023 at 10:36:13 PM UTC-4, Beliavsky wrote:
https://github.com/mherrmann/fix is a project using ChatGPT to fix
errors in a user's C++ code. The same procedure could be used to prompt
ChatGPT to fix code it generates with feedback from the compiler. If such >> tools are created for Fortran it will raise the productivity of Fortran
programmers, especially newer ones. It is also possible that resources such
as Stack Overflow and now ChatGPT make people lazy and less likely to read >> books to understand the programming languages they use.
I wrote a Python program at https://github.com/Beliavsky/ChatGPT-Fortran-generator that will iteratively present ChatGPT with a Fortran code and a compiler error message and ask for a fix. You do need a paid account to use it, but the cost for ChatGPT 3.5 is very low. I have submitted hundreds of queries and paid less than $0.20.
I do not recommend ChatGPT for serious programming work. In principle,
it could become a valuable resource. However, it would require a
specific training that is currently lacking.
As an illustration, I can show herefollowing a recent interaction I had
on the topic of Fortran pointers. Even if somewhat long, it may be interesting.
It is , I have been wanting to see such a thing for a long time. I'm not interested enough to create an account with one of the chatbots to experiment myself but it's good to see an actual transcript as opposed to theoretical claims that chatbots can be used for debugging.
From the experiences people have posted on newsgroups I visit , chatbots
at present do not seem any good at technical stuff. They're fine for "blah blah" stuff. So if anyone wants a poem on , say , how Fortran is great for numerical analysis code , I'm sure the chatbots will do a great job. But
for actual code , I doubt it. Around similar lines , see also the following
2 threads :
From: Sylvia Else <
sylvia@email.invalid>
Newsgroups: comp.misc
Subject: ChatGPT fails at algebra
Date: Thu, 9 Feb 2023 16:10:31 +1100
Message-ID: <
k4jdi7Ft1ikU1@mid.individual.net>
From: Sylvia Else <
sylvia@email.invalid>
Newsgroups: comp.misc
Subject: Trying to teach ChatGPT algebra
Date: Sat, 11 Feb 2023 09:45:29 +1100
Message-ID: <
k4nvo9Fk1erU1@mid.individual.net>
Giorgio
==
User (me) : what will be the output of this piece of code?
program abc
implicit none
integer, pointer :: a,b,c
allocate(b,c)
b=42
c=1
b
c
print*,a,b,c
ChatGPT
Based on the provided code snippet, the output will be:
1 42 1
Here's the explanation:
1. The variables a, b, and c are declared as integer pointers using
the pointer attribute.
2. Memory is allocated for the variables b and c using the allocate statement.
3. The value 42 is assigned to b (b = 42).
4. The value 1 is assigned to c (c = 1).
5. The pointer a is assigned to point to b (a => b).
6. The pointer b is assigned to point to c (b => c).
7. Finally, the values of a, b, and c are printed using the print statement, resulting in the output 1 42 1.
User
After your point 5, I would expect that printing a and b would give 42
and 42. after point 6, printing b and c should give 1 and 1. Am I wrong? ChatGPT
Apologies for the confusion. You are correct. After point 5, printing a
and b will give the output 42 42. After point 6, printing b and c will
give the output 1 1. Here's the corrected explanation:
1. The variables a, b, and c are declared as integer pointers using
the pointer attribute.
2. Memory is allocated for the variables b and c using the allocate statement.
3. The value 42 is assigned to b (b = 42).
4. The value 1 is assigned to c (c = 1).
5. The pointer a is assigned to point to b (a => b).
6. The pointer b is assigned to point to c (b => c).
7. Finally, the values of a, b, and c are printed using the print statement, resulting in the output 42 42 1.
User
I am confused. If, after point 6, b and c will be printed as '1 1', the
only doubt remains on the value printed in correspondence with a. Shoud
it be '1 1 1' or '42 1 1'?
ChatGPT
Apologies for the confusion caused by my previous response. After point
6, printing a, b, and c will give the output 1 1 1.
Here's the corrected explanation:
1. The variables a, b, and c are declared as integer pointers using
the pointer attribute.
2. Memory is allocated for the variables b and c using the allocate statement.
3. The value 42 is assigned to b (b = 42).
4. The value 1 is assigned to c (c = 1).
5. The pointer a is assigned to point to b (a => b).
6. The pointer b is assigned to point to c (b => c).
7. Finally, the values of a, b, and c are printed using the print statement, resulting in the output 1 1 1.
User
Then, if, compiling the program with gfortran, I get '42 1 1' should be considered a compiler error?
ChatGPT
Apologies for the confusion caused by my previous responses. You are
correct. Compiling the program with gfortran and getting the output 42 1
1 indicates a discrepancy with the expected behavior according to the
Fortran code you provided.
In Fortran, when you use pointer assignment (=>), the target variable
takes on the value and type of the pointed-to variable. Therefore, after
the line b => c, the value of b should be 1 rather than 42. The
subsequent print statement should output 1 1 1.
If the compiler produces the output 42 1 1, it suggests a potential
issue with the compiler or the code itself. It's recommended to
double-check the code and ensure there are no other modifications or
factors affecting the behavior. Additionally, consider using the latest version of gfortran or an alternative Fortran compiler to see if the
issue persists.
User
What is, according to the Fortran standard, the exact meaning of a=>b :
1) a is pointing the the memory location pointed by b at the time the instruction is executed, or 2) is pointing to b even if after that instruction b is made pointing to another memory location
ChatGPT
According to the Fortran standard, when you use the pointer assignment a
b, it establishes the association that a is pointing to the memory
location pointed by b at the time the instruction is executed (Option 1
in your question).
Once the pointer association a => b is made, a will continue to point to
the memory location originally pointed by b. Any subsequent changes to b
will not affect the association between a and the original memory
location. Therefore, even if b is made to point to another memory
location after the pointer association is established, a will still
point to the original memory location.
In the code you provided earlier, the output 42 1 1 suggests that the compiler might not be adhering strictly to the Fortran standard in this particular case. The behavior may vary depending on the compiler and its specific implementation of pointer assignments.
User
At this point I do not understand your answer. You said that a continues pointing to the original location of b. That location contains the
integer 42. b at the time the print statemt is executed, b points to c,
so both b and c should be printed as 1. Why you say that '42 1 1' is
not the expected output?
ChatGPT
Apologies for the confusion caused by my previous responses. You are
correct, and I apologize for the incorrect information in my previous explanations.
In the code you provided, after the pointer assignments a => b and b =>
c, the expected output should indeed be 42 1 1.
The pointer assignment a => b establishes that a is pointing to the
memory location pointed by b, which initially contains the value 42.
Then, the pointer assignment b => c changes the pointer b to point to
the memory location pointed by c, which contains the value 1. However,
the pointer assignment does not affect the existing pointer a, so a
still points to the original memory location containing 42.
Therefore, the correct output of the program should be 42 1 1. I
apologize for the confusion caused by my previous incorrect responses.
Can't fault it for politeness :-D
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