[FileFormats.MPS] fix parsing of OBJSENSE (#2016)

Author: odow

src/FileFormats/MPS/MPS.jl

@@ -1050,7 +1050,7 @@ function Headers(s::AbstractString)
         if (x == 'I' || x == 'i') && uppercase(s) == "INDICATORS"
             return HEADER_INDICATORS
         end
-    elseif N == 12
+    elseif N == 8 || N == 12
         if (x == 'O' || x == 'o') && startswith(uppercase(s), "OBJSENSE")
             return HEADER_OBJSENSE
         end
@@ -1092,10 +1092,13 @@ function Base.read!(io::IO, model::Model)
         h = Headers(line)
         if h == HEADER_OBJSENSE
             items = line_to_items(line)
-            @assert length(items) == 2
-            sense = uppercase(items[2])
-            @assert sense == "MAX" || sense == "MIN"
-            data.is_minimization = sense == "MIN"
+            if length(items) == 2
+                sense = uppercase(items[2])
+                @assert sense == "MAX" || sense == "MIN"
+                data.is_minimization = sense == "MIN"
+            else
+                header = HEADER_OBJSENSE
+            end
             continue
         elseif h == HEADER_QCMATRIX || h == HEADER_QSECTION
             items = line_to_items(line)
@@ -1114,6 +1117,11 @@ function Base.read!(io::IO, model::Model)
         items = line_to_items(line)
         if header == HEADER_NAME
             parse_name_line(data, items)
+        elseif header == HEADER_OBJSENSE
+            @assert length(items) == 1
+            sense = uppercase(items[1])
+            @assert sense == "MAX" || sense == "MIN"
+            data.is_minimization = sense == "MIN"
         elseif header == HEADER_ROWS
             multi_obj = parse_rows_line(data, items)
             if multi_obj !== nothing

test/FileFormats/MPS/MPS.jl

@@ -953,6 +953,43 @@ function test_vector_supports_constraint()
     return
 end
 
+function test_objsense_next_line()
+    for (sense, enum) in [("MIN", MOI.MIN_SENSE), ("MAX", MOI.MAX_SENSE)]
+        io = IOBuffer()
+        write(
+            io,
+            """
+            NAME          model
+            OBJSENSE
+            $sense
+            ROWS
+            N  Obj
+            """,
+        )
+        seekstart(io)
+        model = MPS.Model()
+        Base.read!(io, model)
+        @test MOI.get(model, MOI.ObjectiveSense()) == enum
+    end
+    for (sense, enum) in [("MIN", MOI.MIN_SENSE), ("MAX", MOI.MAX_SENSE)]
+        io = IOBuffer()
+        write(
+            io,
+            """
+            NAME          model
+            OBJSENSE $sense
+            ROWS
+            N  Obj
+            """,
+        )
+        seekstart(io)
+        model = MPS.Model()
+        Base.read!(io, model)
+        @test MOI.get(model, MOI.ObjectiveSense()) == enum
+    end
+    return
+end
+
 function runtests()
     for name in names(@__MODULE__, all = true)
         if startswith("$(name)", "test_")