# setWalkTrace -- set value of walkTrace

## Synopsis

• Usage:
setWalkTrace(n)
• Inputs:
• n, an integer, the desired value of walkTrace

## Description

The value of walkTrace determines how much additional information is printed during a call to groebnerWalk. The function setWalkTrace allows the user to change the value of walkTrace.

Levels of walkTrace are as follows:

Level 0: No additional information is printed. This is the default level.

Level 1: The total number of conversions performed during the algorithm is printed at the end of the computation. Conversions are sometimes done in initialization and finalization at the start and end of the path, and otherwise happen at faces in the Groebner fan.

Level 2: All Level 1 information is printed, and the current vector and size of the Groebner basis are printed at each conversion step. Since information is printed at each conversion, this level is helpful for verifying that the computation is proceeding and noticing where the algorithm gets stuck.

Level 3: All Level 2 information is printed, and the codimension of the face in the Groebner fan where the conversion is taking place is printed at each conversion. Note that running on Level 3 will significantly slow down the computation, and is not recommended except for testing.

For example, running the following code at the default Level 0 prints nothing

 i1 : R1 = ZZ/32003[x,y,z, MonomialOrder=>Weights=>{1,10,100}]; i2 : I1 = ideal(y-x^2, z-x^3); o2 : Ideal of R1 i3 : R2 = ZZ/32003[x,y,z, MonomialOrder=>Lex]; i4 : groebnerWalk(gb I1, R2) o4 = GroebnerBasis[status: done; S-pairs encountered up to degree 0] o4 : GroebnerBasis

while running at Level 2 gives some conversion information.

 i5 : setWalkTrace 2; i6 : groebnerWalk(gb I1, R2) Conversion Number: 1 Weight Vector: {1, 10, 100} Size of new Groebner Basis: 2 Conversion Number: 2 Weight Vector: {1, 2, 20} Size of new Groebner Basis: 2 Conversion Number: 3 Weight Vector: {9, 1, 10} Size of new Groebner Basis: 4 Conversion Number: 4 Weight Vector: {1, 0, 0} Size of new Groebner Basis: 4 Conversion Number: 5 Weight Vector: {1, 0, 0} Size of new Groebner Basis: 4 Total Conversions: 5 o6 = GroebnerBasis[status: done; S-pairs encountered up to degree 0] o6 : GroebnerBasis