How have courts interpreted judicial discretion in sentencing sentencing decisions?

"It is well established that a trial court has discretion to determine whether . . . sentences are to run concurrently or consecutively. (Pen. Code, 669[, subd. (a)]; [citation].) It is also the rule that appellate courts do not have the power to modify a sentence or reduce the punishment therein imposed absent error in the proceedings. [Citation.] Moreover, such error cannot be predicated on a trial court's determination that several sentences are to run consecutively unless an abuse of discretion is clearly shown. [Citations.] [] The concept of judicial discretion is difficult to define with precision. In the past we have described it as 'the sound judgment of the court, to be exercised according to the rules of law.' [Citation.] More recently we have said (quoting from another case) that the term judicial discretion 'implies absence of arbitrary determination, capricious disposition or whimsical thinking.' [Citation.] Moreover, discretion is abused whenever the court exceeds the bounds of reason, all of the circumstances being considered. [Citations.] However, in the absence of a clear showing that its sentencing decision was arbitrary or irrational, a trial court should be presumed to have acted to achieve legitimate sentencing objectives and, accordingly, its discretionary determination to impose consecutive sentences ought not be set aside on review." (People v. Giminez (1975) 14 Cal.3d 68, 71-72.)