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From: |
MASATO KOIZUMI <mkoizumi@...3709...> |

Date: |
Thu, 27 Jul 2017 13:08:26 -0700 |

Dear Dr. Axel Kohlmeyer,

Hello Dr. Kohlmeyer. Thank you for your e-mail. I was curious if this bug is intrinsic to LAMMPS or I was curious if there is a way in solving this problem since I have (-1) raised to a power of a number. Thank you.

Sincerely,

Masato Koizumi

On Thu, Jul 27, 2017 at 12:51 PM, Axel Kohlmeyer <akohlmey@...24...> wrote:

>> variable displace equal "v_L0 + (0.5*v_L0)*(1 +

>> (2/PI)*asin(sin((2*PI*(1/v_Tp)*step*dt) - (PI/2))))"

>> variable rate equal "(2*v_L0*(1/v_Tp))*(-1)^floor(2*(1/v_Tp)*step*dt)"

>> fix 4 all deform 1 x variable v_displace v_rate remap v

>>

>>

>> However, I obtained an error statement: ERROR: Power by 0 in variable

>> formula (../variable.cpp:1718)

>>

>> Even when I looked at the LAMMPS error manual, I am not understanding this

>> error since my variable formula does not have a zero powered to a number. I

>

> that is not what the error message says. it says that you have a

> number raised to the power of 0.

that said, LAMMPS should not stop with an error here.

x^0 should always result in 1.0 for any value of x, even for x == NaN.

instead 0^y with y < 0.0 should be disallowed, as this is equivalent

to 1.0/0^-y and thus would cause a division by zero.

so the current behavior of LAMMPS is actually a bug.

axel

>

> axel.

>

--

Dr. Axel Kohlmeyer akohlmey@...43...4... http://goo.gl/1wk0

College of Science & Technology, Temple University, Philadelphia PA, USA

International Centre for Theoretical Physics, Trieste. Italy.

**References**:**Re: [lammps-users] Inquiry on LAMMPS fix_deform and variable formula"***From:*MASATO KOIZUMI <mkoizumi@...3709...>

**Re: [lammps-users] Inquiry on LAMMPS fix_deform and variable formula"***From:*Axel Kohlmeyer <akohlmey@...24...>

**Re: [lammps-users] Inquiry on LAMMPS fix_deform and variable formula"***From:*Axel Kohlmeyer <akohlmey@...24...>

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