Minor improvements

src/LAMMPS.jl

@@ -3,7 +3,7 @@ import MPI
 include("api.jl")
 
 export LMP, command, get_natoms, extract_atom, extract_compute, extract_global,
-       gather, scatter!
+       gather, scatter!, group_to_atom_ids, get_category_ids, close!
 
 using Preferences
 
@@ -47,6 +47,11 @@ function set_library!(path)
     end
 end
 
+"""
+    LMP(args::Vector{String}=String[], comm::Union{Nothing, MPI.Comm}=nothing)
+
+Create a new LAMMPS instance while passing in a list of strings as if they were command-line arguments for the LAMMPS executable.
+"""
 mutable struct LMP
     @atomic handle::Ptr{Cvoid}
 
@@ -77,7 +82,7 @@ Base.unsafe_convert(::Type{Ptr{Cvoid}}, lmp::LMP) = lmp.handle
 """
     close!(lmp::LMP)
 
-Shutdown an LMP instance.
+Shutdown an LAMMPS instance.
 """
 function close!(lmp::LMP)
     handle = @atomicswap lmp.handle = C_NULL
@@ -86,9 +91,17 @@ function close!(lmp::LMP)
     end
 end
 
+"""
+    LMP(f::Function, args=String[], comm=nothing)
+
+Create a new LAMMPS instance and call `f` on that instance while returning the result from `f`.
+This constructor closes the LAMMPS instance immediately after `f` has executed.
+"""
 function LMP(f::Function, args=String[], comm=nothing)
     lmp = LMP(args, comm)
-    f(lmp)
+    result = f(lmp)
+    close!(lmp)
+    return result
 end
 
 function version(lmp::LMP)
@@ -101,18 +114,38 @@ function check(lmp::LMP)
         # TODO: Check err == 1 or err == 2 (MPI)
         buf = zeros(UInt8, 100)
         API.lammps_get_last_error_message(lmp, buf, length(buf))
-        error(String(buf))
+        error(rstrip(String(buf), '\0'))
     end
 end
 
 
 """
-    command(lmp::lmp, cmd)
+    command(lmp::LMP, cmd::Union{String, Array{String}})
+
+Process LAMMPS input commands from a String or from an Array of Strings.
+
+For a full list of commands see: https://docs.lammps.org/commands_list.html
+
+This function processes a multi-line string similar to a block of commands from a file.
+The string may have multiple lines (separated by newline characters) and also single commands may
+be distributed over multiple lines with continuation characters (’&’).
+Those lines are combined by removing the ‘&’ and the following newline character.
+After this processing the string is handed to LAMMPS for parsing and executing.
+
+Arrays of Strings get concatenated into a single String inserting newline characters as needed.
+
+!!! warn "Newline Characters"
+    Old versions of this package (0.4.0 or older) used to ignore newline characters,
+    such that `cmd` would allways be treated as a single command. In newer version this is no longer the case.
 """
-function command(lmp::LMP, cmd)
-    ptr = API.lammps_command(lmp, cmd)
-    ptr == C_NULL && check(lmp)
-    nothing
+function command(lmp::LMP, cmd::Union{String, Array{String}})
+    if cmd isa String
+        API.lammps_commands_string(lmp, cmd)
+    else
+        API.lammps_commands_list(lmp, length(cmd), cmd)
+    end
+
+    check(lmp)
 end
 
 """
@@ -507,4 +540,59 @@ function _get_T(lmp::LMP, name::String)
 
 end
 
+"""
+    group_to_atom_ids(lmp::LMP, group::String)
+
+Find the IDs of the Atoms in the group.
+"""
+function group_to_atom_ids(lmp::LMP, group::String)
+    # Pad with '\0' to avoid confusion with groups names that are truncated versions of name
+    # For example 'all' could be confused with 'a'
+    name_padded = codeunits(group * '\0')
+    buffer_size = length(name_padded)
+    buffer = zeros(UInt8, buffer_size)
+
+    ngroups = API.lammps_id_count(lmp, "group")
+
+    for idx in 0:ngroups-1
+        API.lammps_id_name(lmp, "group", idx, buffer, buffer_size)
+        buffer != name_padded && continue
+
+        mask = gather(lmp, "mask", Int32)[:] .& (1 << idx) .!= 0
+        all_ids = UnitRange{Int32}(1, get_natoms(lmp))
+
+        return all_ids[mask]
+    end
+
+    error("Cannot find group $group")
+end
+
+
+"""
+    get_category_ids(lmp::LMP, category::String, buffer_size::Integer=50)
+
+Look up the names of entities within a certain category.
+
+Valid categories are: compute, dump, fix, group, molecule, region, and variable.
+names longer than `buffer_size` will be truncated to fit inside the buffer.
+"""
+function get_category_ids(lmp::LMP, category::String, buffer_size::Integer=50)
+    _check_valid_category(category)
+
+    count = API.lammps_id_count(lmp, category)
+    check(lmp)
+
+    res = Vector{String}(undef, count)
+
+    for i in 1:count
+        buffer = zeros(UInt8, buffer_size)
+        API.lammps_id_name(lmp, category, i-1, buffer, buffer_size)
+        res[i] = rstrip(String(buffer), '\0')
+    end
+
+    return res
+end
+
+_check_valid_category(category::String) = category in ("compute", "dump", "fix", "group", "molecule", "region", "variable") || error("$category is not a valid category name!")
+
 end # module

test/runtests.jl

@@ -101,4 +101,39 @@ end
     end
 end
 
+@testset "Utilities" begin
+    LMP(["-screen", "none"]) do lmp
+        # setting up example data
+        command(lmp, """
+            atom_modify map yes
+            region cell block 0 2 0 2 0 2
+            create_box 1 cell
+            lattice sc 1
+            create_atoms 1 region cell
+            mass 1 1
+
+            group a id 1 2 3 5 8
+            group even id 2 4 6 8
+            group odd id 1 3 5 7
+        """)
+
+        @test group_to_atom_ids(lmp, "all") == 1:8
+        @test group_to_atom_ids(lmp, "a") == [1, 2, 3, 5, 8]
+        @test group_to_atom_ids(lmp, "even") == [2, 4, 6, 8]
+        @test group_to_atom_ids(lmp, "odd") == [1, 3, 5, 7]
+        @test_throws ErrorException group_to_atom_ids(lmp, "nonesense")
+
+        command(lmp, [
+            "compute pos all property/atom x y z",
+            "fix 1 all ave/atom 10 1 10 c_pos[*]",
+            "run 10"
+        ])
+
+        @test get_category_ids(lmp, "group") == ["all", "a", "even", "odd"]
+        @test get_category_ids(lmp, "compute") == ["thermo_temp", "thermo_press", "thermo_pe", "pos"] # some of these computes are there by default it seems
+        @test get_category_ids(lmp, "fix") == ["1"]
+        @test_throws ErrorException get_category_ids(lmp, "nonesense")
+    end
+end
+
 @test success(pipeline(`$(MPI.mpiexec()) -n 2 $(Base.julia_cmd()) mpitest.jl`, stderr=stderr, stdout=stdout))