move sanity check on math to where the math is done, and further provide against accumulative sanity checking
move sanity check on math to where the math is done, and further provide against accumulative sanity checking

git-svn-id: ae92b08b608af1c8cefa3e10d2325ea527204e07@25237 3eda493b-6a19-0410-b2e0-ec8ea4dd8fda

pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable