2016-05-10 01:33:12 +08:00
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2016-09-14 08:22:17 +08:00
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2016-05-10 01:33:12 +08:00
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< li class = "toctree-l1" > < a class = "reference internal" href = "Section_intro.html" > 1. Introduction< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_start.html" > 2. Getting Started< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_commands.html" > 3. Commands< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_packages.html" > 4. Packages< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_accelerate.html" > 5. Accelerating LAMMPS performance< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_howto.html" > 6. How-to discussions< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_example.html" > 7. Example problems< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_perf.html" > 8. Performance & scalability< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_tools.html" > 9. Additional tools< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_modify.html" > 10. Modifying & extending LAMMPS< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_python.html" > 11. Python interface to LAMMPS< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_errors.html" > 12. Errors< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "Section_history.html" > 13. Future and history< / a > < / li >
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2016-09-14 08:22:17 +08:00
< p class = "caption" > < span class = "caption-text" > Index< / span > < / p >
< ul class = "current" >
< li class = "toctree-l1" > < a class = "reference internal" href = "tutorials.html" > Tutorials< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "commands.html" > Commands< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "fixes.html" > Fixes< / a > < / li >
< li class = "toctree-l1 current" > < a class = "reference internal" href = "computes.html" > Computes< / a > < ul class = "current" >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_ackland_atom.html" > compute ackland/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_angle.html" > compute angle command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_angle_local.html" > compute angle/local command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_angmom_chunk.html" > compute angmom/chunk command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_basal_atom.html" > compute basal/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_body_local.html" > compute body/local command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_bond.html" > compute bond command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_bond_local.html" > compute bond/local command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_centro_atom.html" > compute centro/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_chunk_atom.html" > compute chunk/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_cluster_atom.html" > compute cluster/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_cna_atom.html" > compute cna/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_com.html" > compute com command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_com_chunk.html" > compute com/chunk command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_contact_atom.html" > compute contact/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_coord_atom.html" > compute coord/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_damage_atom.html" > compute damage/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_dihedral.html" > compute dihedral command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_dihedral_local.html" > compute dihedral/local command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_dilatation_atom.html" > compute dilatation/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_dipole_chunk.html" > compute dipole/chunk command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_displace_atom.html" > compute displace/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_dpd.html" > compute dpd command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_dpd_atom.html" > compute dpd/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_erotate_asphere.html" > compute erotate/asphere command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_erotate_rigid.html" > compute erotate/rigid command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_erotate_sphere.html" > compute erotate/sphere command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_erotate_sphere_atom.html" > compute erotate/sphere/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_event_displace.html" > compute event/displace command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_fep.html" > compute fep command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_group_group.html" > compute group/group command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_gyration.html" > compute gyration command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_gyration_chunk.html" > compute gyration/chunk command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_heat_flux.html" > compute heat/flux command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_hexorder_atom.html" > compute hexorder/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_improper.html" > compute improper command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_improper_local.html" > compute improper/local command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_inertia_chunk.html" > compute inertia/chunk command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_ke.html" > compute ke command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_ke_atom.html" > compute ke/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_ke_atom_eff.html" > compute ke/atom/eff command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_ke_eff.html" > compute ke/eff command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_ke_rigid.html" > compute ke/rigid command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_meso_e_atom.html" > compute meso/e/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_meso_rho_atom.html" > compute meso/rho/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_meso_t_atom.html" > compute meso/t/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_msd.html" > compute msd command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_msd_chunk.html" > compute msd/chunk command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_msd_nongauss.html" > compute msd/nongauss command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_omega_chunk.html" > compute omega/chunk command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_orientorder_atom.html" > compute orientorder/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_pair.html" > compute pair command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_pair_local.html" > compute pair/local command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_pe.html" > compute pe command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_pe_atom.html" > compute pe/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_plasticity_atom.html" > compute plasticity/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_pressure.html" > compute pressure command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_property_atom.html" > compute property/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_property_chunk.html" > compute property/chunk command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_property_local.html" > compute property/local command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_rdf.html" > compute rdf command< / a > < / li >
< li class = "toctree-l2 current" > < a class = "current reference internal" href = "#" > compute reduce command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "#compute-reduce-region-command" > compute reduce/region command< / a > < ul >
< li class = "toctree-l3" > < a class = "reference internal" href = "#syntax" > Syntax< / a > < / li >
< li class = "toctree-l3" > < a class = "reference internal" href = "#examples" > Examples< / a > < / li >
< li class = "toctree-l3" > < a class = "reference internal" href = "#description" > Description< / a > < / li >
< li class = "toctree-l3" > < a class = "reference internal" href = "#restrictions" > Restrictions< / a > < / li >
< li class = "toctree-l3" > < a class = "reference internal" href = "#related-commands" > Related commands< / a > < / li >
< / ul >
< / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_rigid_local.html" > compute rigid/local command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_saed.html" > compute saed command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_slice.html" > compute slice command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_contact_radius.html" > compute smd/contact/radius command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_damage.html" > compute smd/damage command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_hourglass_error.html" > compute smd/hourglass/error command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_internal_energy.html" > compute smd/internal/energy command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_plastic_strain.html" > compute smd/plastic/strain command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_plastic_strain_rate.html" > compute smd/plastic/strain/rate command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_rho.html" > compute smd/rho command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_tlsph_defgrad.html" > compute smd/tlsph/defgrad command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_tlsph_dt.html" > compute smd/tlsph/dt command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_tlsph_num_neighs.html" > compute smd/tlsph/num/neighs command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_tlsph_shape.html" > compute smd/tlsph/shape command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_tlsph_strain.html" > compute smd/tlsph/strain command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_tlsph_strain_rate.html" > compute smd/tlsph/strain/rate command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_tlsph_stress.html" > compute smd/tlsph/stress command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_triangle_mesh_vertices.html" > compute smd/triangle/mesh/vertices< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_ulsph_num_neighs.html" > compute smd/ulsph/num/neighs command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_ulsph_strain.html" > compute smd/ulsph/strain command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_ulsph_strain_rate.html" > compute smd/ulsph/strain/rate command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_ulsph_stress.html" > compute smd/ulsph/stress command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_smd_vol.html" > compute smd/vol command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_sna_atom.html" > compute sna/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_sna_atom.html#compute-snad-atom-command" > compute snad/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_sna_atom.html#compute-snav-atom-command" > compute snav/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_stress_atom.html" > compute stress/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_tally.html" > compute force/tally command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_tally.html#compute-heat-flux-tally-command" > compute heat/flux/tally command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_tally.html#compute-pe-tally-command" > compute pe/tally command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_tally.html#compute-pe-mol-tally-command" > compute pe/mol/tally command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_tally.html#compute-stress-tally-command" > compute stress/tally command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp.html" > compute temp command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp.html#compute-temp-kk-command" > compute temp/kk command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp_asphere.html" > compute temp/asphere command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp_body.html" > compute temp/body command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp_chunk.html" > compute temp/chunk command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp_com.html" > compute temp/com command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp_cs.html" > compute temp/cs command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp_deform.html" > compute temp/deform command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp_deform_eff.html" > compute temp/deform/eff command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp_drude.html" > compute temp/drude command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp_eff.html" > compute temp/eff command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp_partial.html" > compute temp/partial command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp_profile.html" > compute temp/profile command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp_ramp.html" > compute temp/ramp command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp_region.html" > compute temp/region command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp_region_eff.html" > compute temp/region/eff command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp_rotate.html" > compute temp/rotate command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_temp_sphere.html" > compute temp/sphere command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_ti.html" > compute ti command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_torque_chunk.html" > compute torque/chunk command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_vacf.html" > compute vacf command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_vcm_chunk.html" > compute vcm/chunk command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_voronoi_atom.html" > compute voronoi/atom command< / a > < / li >
< li class = "toctree-l2" > < a class = "reference internal" href = "compute_xrd.html" > compute xrd command< / a > < / li >
< / ul >
< / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "pairs.html" > Pair Styles< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "bonds.html" > Bonds< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "angles.html" > Angle Styles< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "dihedrals.html" > Dihedral Styles< / a > < / li >
< li class = "toctree-l1" > < a class = "reference internal" href = "impropers.html" > Improper Styles< / a > < / li >
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2016-05-10 01:33:12 +08:00
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< div class = "section" id = "compute-reduce-command" >
< span id = "index-0" > < / span > < h1 > compute reduce command< / h1 >
< / div >
< div class = "section" id = "compute-reduce-region-command" >
< h1 > compute reduce/region command< / h1 >
< div class = "section" id = "syntax" >
< h2 > Syntax< / h2 >
< div class = "highlight-default" > < div class = "highlight" > < pre > < span > < / span > < span class = "n" > compute< / span > < span class = "n" > ID< / span > < span class = "n" > group< / span > < span class = "o" > -< / span > < span class = "n" > ID< / span > < span class = "n" > style< / span > < span class = "n" > arg< / span > < span class = "n" > mode< / span > < span class = "n" > input1< / span > < span class = "n" > input2< / span > < span class = "o" > ...< / span > < span class = "n" > keyword< / span > < span class = "n" > args< / span > < span class = "o" > ...< / span >
< / pre > < / div >
< / div >
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< ul >
< li > < p class = "first" > ID, group-ID are documented in < a class = "reference internal" href = "compute.html" > < span class = "doc" > compute< / span > < / a > command< / p >
< / li >
< li > < p class = "first" > style = < em > reduce< / em > or < em > reduce/region< / em > < / p >
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< pre class = "literal-block" >
< em > reduce< / em > arg = none
< em > reduce/region< / em > arg = region-ID
region-ID = ID of region to use for choosing atoms
< / pre >
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< / li >
< li > < p class = "first" > mode = < em > sum< / em > or < em > min< / em > or < em > max< / em > or < em > ave< / em > or < em > sumsq< / em > or < em > avesq< / em > < / p >
< / li >
< li > < p class = "first" > one or more inputs can be listed< / p >
< / li >
< li > < p class = "first" > input = x, y, z, vx, vy, vz, fx, fy, fz, c_ID, c_ID[N], f_ID, f_ID[N], v_name< / p >
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< pre class = "literal-block" >
x,y,z,vx,vy,vz,fx,fy,fz = atom attribute (position, velocity, force component)
c_ID = per-atom or local vector calculated by a compute with ID
c_ID[I] = Ith column of per-atom or local array calculated by a compute with ID, I can include wildcard (see below)
f_ID = per-atom or local vector calculated by a fix with ID
f_ID[I] = Ith column of per-atom or local array calculated by a fix with ID, I can include wildcard (see below)
v_name = per-atom vector calculated by an atom-style variable with name
< / pre >
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< / li >
< li > < p class = "first" > zero or more keyword/args pairs may be appended< / p >
< / li >
< li > < p class = "first" > keyword = < em > replace< / em > < / p >
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< pre class = "literal-block" >
< em > replace< / em > args = vec1 vec2
vec1 = reduced value from this input vector will be replaced
vec2 = replace it with vec1[N] where N is index of max/min value from vec2
< / pre >
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< / li >
< / ul >
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< / div >
< div class = "section" id = "examples" >
< h2 > Examples< / h2 >
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< pre class = "literal-block" >
compute 1 all reduce sum c_force
compute 1 all reduce/region subbox sum c_force
compute 2 all reduce min c_press[2] f_ave v_myKE
compute 2 all reduce min c_press[*] f_ave v_myKE
compute 3 fluid reduce max c_index[1] c_index[2] c_dist replace 1 3 replace 2 3
< / pre >
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< / div >
< div class = "section" id = "description" >
< h2 > Description< / h2 >
< p > Define a calculation that “ reduces” one or more vector inputs into
scalar values, one per listed input. The inputs can be per-atom or
local quantities; they cannot be global quantities. Atom attributes
are per-atom quantities, < a class = "reference internal" href = "compute.html" > < span class = "doc" > computes< / span > < / a > and < a class = "reference internal" href = "fix.html" > < span class = "doc" > fixes< / span > < / a >
may generate any of the three kinds of quantities, and < a class = "reference internal" href = "variable.html" > < span class = "doc" > atom-style variables< / span > < / a > generate per-atom quantities. See the
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< a class = "reference internal" href = "variable.html" > < span class = "doc" > variable< / span > < / a > command and its special functions which can
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perform the same operations as the compute reduce command on global
vectors.< / p >
< p > The reduction operation is specified by the < em > mode< / em > setting. The < em > sum< / em >
option adds the values in the vector into a global total. The < em > min< / em >
or < em > max< / em > options find the minimum or maximum value across all vector
values. The < em > ave< / em > setting adds the vector values into a global total,
then divides by the number of values in the vector. The < em > sumsq< / em >
option sums the square of the values in the vector into a global
total. The < em > avesq< / em > setting does the same as < em > sumsq< / em > , then divdes the
sum of squares by the number of values. The last two options can be
useful for calculating the variance of some quantity, e.g. variance =
sumsq - ave^2.< / p >
< p > Each listed input is operated on independently. For per-atom inputs,
the group specified with this command means only atoms within the
group contribute to the result. For per-atom inputs, if the compute
reduce/region command is used, the atoms must also currently be within
the region. Note that an input that produces per-atom quantities may
define its own group which affects the quantities it returns. For
example, if a compute is used as an input which generates a per-atom
vector, it will generate values of 0.0 for atoms that are not in the
group specified for that compute.< / p >
< p > Each listed input can be an atom attribute (position, velocity, force
component) or can be the result of a < a class = "reference internal" href = "compute.html" > < span class = "doc" > compute< / span > < / a > or
< a class = "reference internal" href = "fix.html" > < span class = "doc" > fix< / span > < / a > or the evaluation of an atom-style
< a class = "reference internal" href = "variable.html" > < span class = "doc" > variable< / span > < / a > .< / p >
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< p > Note that for values from a compute or fix, the bracketed index I can
be specified using a wildcard asterisk with the index to effectively
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specify multiple values. This takes the form “ *” or “ *n” or “ n*” or
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“ m*n” . If N = the size of the vector (for < em > mode< / em > = scalar) or the
number of columns in the array (for < em > mode< / em > = vector), then an asterisk
with no numeric values means all indices from 1 to N. A leading
asterisk means all indices from 1 to n (inclusive). A trailing
asterisk means all indices from n to N (inclusive). A middle asterisk
means all indices from m to n (inclusive).< / p >
< p > Using a wildcard is the same as if the individual columns of the array
had been listed one by one. E.g. these 2 compute reduce commands are
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equivalent, since the < a class = "reference internal" href = "compute_stress_atom.html" > < span class = "doc" > compute stress/atom< / span > < / a >
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command creates a per-atom array with 6 columns:< / p >
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< pre class = "literal-block" >
compute myPress all stress/atom NULL
compute 2 all reduce min myPress[*]
compute 2 all reduce min myPress[1] myPress[2] myPress[3] &
myPress[4] myPress[5] myPress[6]
< / pre >
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< hr class = "docutils" / >
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< p > The atom attribute values (x,y,z,vx,vy,vz,fx,fy,fz) are
self-explanatory. Note that other atom attributes can be used as
inputs to this fix by using the < a class = "reference internal" href = "compute_property_atom.html" > < span class = "doc" > compute property/atom< / span > < / a > command and then specifying
an input value from that compute.< / p >
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< p > If a value begins with “ c_” , a compute ID must follow which has been
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previously defined in the input script. Computes can generate
per-atom or local quantities. See the individual
< a class = "reference internal" href = "compute.html" > < span class = "doc" > compute< / span > < / a > doc page for details. If no bracketed integer
is appended, the vector calculated by the compute is used. If a
bracketed integer is appended, the Ith column of the array calculated
by the compute is used. Users can also write code for their own
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compute styles and < a class = "reference internal" href = "Section_modify.html" > < span class = "doc" > add them to LAMMPS< / span > < / a > . See the
discussion above for how I can be specified with a wildcard asterisk
to effectively specify multiple values.< / p >
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< p > If a value begins with “ f_” , a fix ID must follow which has been
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previously defined in the input script. Fixes can generate per-atom
or local quantities. See the individual < a class = "reference internal" href = "fix.html" > < span class = "doc" > fix< / span > < / a > doc page for
details. Note that some fixes only produce their values on certain
timesteps, which must be compatible with when compute reduce
references the values, else an error results. If no bracketed integer
is appended, the vector calculated by the fix is used. If a bracketed
integer is appended, the Ith column of the array calculated by the fix
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is used. Users can also write code for their own fix style and < a class = "reference internal" href = "Section_modify.html" > < span class = "doc" > add them to LAMMPS< / span > < / a > . See the discussion above for how
I can be specified with a wildcard asterisk to effectively specify
multiple values.< / p >
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< p > If a value begins with “ v_” , a variable name must follow which has
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been previously defined in the input script. It must be an
< a class = "reference internal" href = "variable.html" > < span class = "doc" > atom-style variable< / span > < / a > . Atom-style variables can
reference thermodynamic keywords and various per-atom attributes, or
invoke other computes, fixes, or variables when they are evaluated, so
this is a very general means of generating per-atom quantities to
reduce.< / p >
< hr class = "docutils" / >
< p > If the < em > replace< / em > keyword is used, two indices < em > vec1< / em > and < em > vec2< / em > are
specified, where each index ranges from 1 to the # of input values.
The replace keyword can only be used if the < em > mode< / em > is < em > min< / em > or < em > max< / em > .
It works as follows. A min/max is computed as usual on the < em > vec2< / em >
input vector. The index N of that value within < em > vec2< / em > is also stored.
Then, instead of performing a min/max on the < em > vec1< / em > input vector, the
stored index is used to select the Nth element of the < em > vec1< / em > vector.< / p >
< p > Thus, for example, if you wish to use this compute to find the bond
with maximum stretch, you can do it as follows:< / p >
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< pre class = "literal-block" >
compute 1 all property/local batom1 batom2
compute 2 all bond/local dist
compute 3 all reduce max c_1[1] c_1[2] c_2 replace 1 3 replace 2 3
thermo_style custom step temp c_3[1] c_3[2] c_3[3]
< / pre >
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< p > The first two input values in the compute reduce command are vectors
with the IDs of the 2 atoms in each bond, using the < a class = "reference internal" href = "compute_property_local.html" > < span class = "doc" > compute property/local< / span > < / a > command. The last input
value is bond distance, using the < a class = "reference internal" href = "compute_bond_local.html" > < span class = "doc" > compute bond/local< / span > < / a > command. Instead of taking the
max of the two atom ID vectors, which does not yield useful
information in this context, the < em > replace< / em > keywords will extract the
atom IDs for the two atoms in the bond of maximum stretch. These atom
IDs and the bond stretch will be printed with thermodynamic output.< / p >
< hr class = "docutils" / >
< p > If a single input is specified this compute produces a global scalar
value. If multiple inputs are specified, this compute produces a
global vector of values, the length of which is equal to the number of
inputs specified.< / p >
< p > As discussed below, for the < em > sum< / em > and < em > sumsq< / em > modes, the value(s)
produced by this compute are all “ extensive” , meaning their value
scales linearly with the number of atoms involved. If normalized
values are desired, this compute can be accessed by the < a class = "reference internal" href = "thermo_style.html" > < span class = "doc" > thermo_style custom< / span > < / a > command with < a class = "reference internal" href = "thermo_modify.html" > < span class = "doc" > thermo_modify norm yes< / span > < / a > set as an option. Or it can be accessed by a
< a class = "reference internal" href = "variable.html" > < span class = "doc" > variable< / span > < / a > that divides by the appropriate atom count.< / p >
< hr class = "docutils" / >
< p > < strong > Output info:< / strong > < / p >
< p > This compute calculates a global scalar if a single input value is
specified or a global vector of length N where N is the number of
inputs, and which can be accessed by indices 1 to N. These values can
be used by any command that uses global scalar or vector values from a
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compute as input. See < a class = "reference internal" href = "Section_howto.html#howto-15" > < span class = "std std-ref" > Section 6.15< / span > < / a >
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for an overview of LAMMPS output options.< / p >
< p > All the scalar or vector values calculated by this compute are
“ intensive” , except when the < em > sum< / em > or < em > sumsq< / em > modes are used on
per-atom or local vectors, in which case the calculated values are
“ extensive” .< / p >
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< p > The scalar or vector values will be in whatever < a class = "reference internal" href = "units.html" > < span class = "doc" > units< / span > < / a > the
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quantities being reduced are in.< / p >
< / div >
< div class = "section" id = "restrictions" >
< h2 > Restrictions< / h2 >
< blockquote >
< div > none< / div > < / blockquote >
< / div >
< div class = "section" id = "related-commands" >
< h2 > Related commands< / h2 >
< p > < a class = "reference internal" href = "compute.html" > < span class = "doc" > compute< / span > < / a > , < a class = "reference internal" href = "fix.html" > < span class = "doc" > fix< / span > < / a > , < a class = "reference internal" href = "variable.html" > < span class = "doc" > variable< / span > < / a > < / p >
< p > < strong > Default:< / strong > none< / p >
< / div >
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