fix two bugs, remove triangularity test

Author: RafaelDavidMohr

src/siggb/siggb.jl

@@ -63,7 +63,7 @@ function sig_groebner_basis(sys::Vector{T}; info_level::Int=0, degbound::Int=0)
     Rchar = characteristic(R)
 
     # check if input is ok
-    if Rchar > 2^31
+    if Rchar > 2^31 || iszero(Rchar)
         error("At the moment we only support finite fields up to prime characteristic < 2^31.")
     end
     sysl = length(sys)

src/siggb/symbolic_pp.jl

@@ -110,14 +110,14 @@ function select_normal!(pairset::Pairset{N},
 
                 add_cond = !iszero(reducer_ind)
                 if add_cond
-                    resize_pivots!(matrix, symbol_ht)
                     mult = divide(monomial(reducer_sig),
                                   monomial(basis.sigs[reducer_ind]))
                     lead_idx = write_to_matrix_row!(matrix, basis,
                                                     reducer_ind,
                                                     symbol_ht, ht, mult,
                                                     reducer_sig)
                     # set pivot
+                    resize_pivots!(matrix, symbol_ht)
                     matrix.pivots[lead_idx] = matrix.nrows
                 end
             end