Formatted thermo keyword in print file-name

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1

Hi!

I want to 'print' to a file, with a name that includes the number of particles
in the system. Additionally, I want to pad it with zeroes, so that the name of
the file is always of a fixed length.

What I need is something like this:

    print "abc" append file_$(atoms:%05d).dat

But that gives me the following error:
"Substitution for illegal variable size (src/input.cpp:545)"

I also tried doing this by defining a 'format' style variable:

    variable size format \(atoms\) %05d     print {size}

But that also results in the same error.

How do I achieve this?

Thanks!
Vishnu

2

Hi!

I want to ‘print’ to a file, with a name that includes the number of particles
in the system. Additionally, I want to pad it with zeroes, so that the name of
the file is always of a fixed length.

What I need is something like this:

print “abc” append file_$(atoms:%05d).dat

But that gives me the following error:
“Substitution for illegal variable size (src/input.cpp:545)”

the print line from above CANNOT produce the error message you quote, since it does not contain any reference to a variable named ‘size’

I also tried doing this by defining a ‘format’ style variable:

variable size format (atoms) %05d print {size}

yes, because that is not the correct syntax. instead of using an immediate variable ‘$(atoms)’ you must use a proper variable, e.g. equal style.

But that also results in the same error.

yes, this will create the error, since your definition of ‘size’ is illegal.

axel.

3

>
> What I need is something like this:
>
> print "abc" append file_$(atoms:%05d).dat
>
> But that gives me the following error:
> "Substitution for illegal variable size (src/input.cpp:545)"
>
>
the print line from above *CANNOT* produce the error message you quote,
since it does not contain any reference to a variable named 'size'

Yes, correct; sorry, I pasted the output of the next command. The actual error
was:

    ERROR on proc 0: Substitution for illegal variable atoms:%05d
(src/input.cpp:545)

Can it not be done this way?

> I also tried doing this by defining a 'format' style variable:
>
> variable size format \(atoms\) %05d > print {size}
>

yes, because that is not the correct syntax. instead of using an immediate
variable '$(atoms)' you must use a proper variable, e.g. equal style.

Okay, so I'm now attempting this:

    variable nums equal atoms
    variable size format nums %05d
    print ${size}

But I must be doing something seriously wrong, because what I get are large,
arbitrary numbers, like: 1318092096, 248134976, -1398260416, 1610366272, etc.

I'm using LAMMPS (15 May 2019).

I'm also attaching a minimal input script that produces this.

in.format (817 Bytes)

4

please file this as a bug report issue on the LAMMPS github project. thanks in advance, axel.

5

on second thought, this is not a bug.
the problem is, that you are applying a %d format, i.e. an 32-bit integer format to a double precision floating point number. you must use %f.

axel.

6

Thanks a lot! It works now!! This gives me exactly what I want:

    variable nums equal atoms
    variable size format nums %05.0f
    print ${size}

But isn't it odd to use floats for the 'atoms' thermo keyword?

7

all equal or atom style variables evaluate to doubles. that saves having to store type information and complicate the already complicated code even more.

i am adding a small test to the code in variable.cpp and input.cpp so that incorrect conversions will trigger an error in the future.

axel.