# Thread: An alternative to computing true count

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## An alternative to computing true count

Blackjack counting methodology dictates making betting and play decisions by calculating true count and and comparing TC to the appropriate index. There is another way to perform this comparison that has some advantages.

From algebra we know that the expression
if true count >= index
which is the same as
if (running count divided by number of decks remaining) >= index
is equivalent to (by multiplying both sides of the expression by number of decks remaining)
if running count >= (index multiplied by number of decks remaining)
Let's define running index (or RI) as index multiplied by the number of decks remaining. Comparing RC to RI will always give the same result as comparing TC to the index.

Here are some of the advantages of RI over TC:
1. Multiplication is much quicker and less error prone than division, especially when the number of decks is not an integer. Moreover, the difference is more pronounced when the number of decks is expressed in smaller units such as quarter decks. Speed is of the essence, not only to conserve mental energy but to enable smooth play without giving a tell (to borrow a poker term) by taking time to calculate TC.

Try doing the math for a case where the running count is 11, the index is 3, and there are 3.5 decks remaining. Using TC you divide 3.5 into 11, getting a true count of 3.14 (or approximated as 3+) which is greater than the index. Using RI, you muliply 3 x 3.5 getting 10.5, and running count is greater than the running index giving the same decision result. Try simple and more complicated cases and I believe you will find the RI is never slower than TC.

2. If you are playing at a table where there are multiple players and are not playing first base, RI has an advantage over TC in that you can calculate the RI as soon as you identify the relevant index for your first decision. Unless the players drawing cards ahead of you take enough cards to change the number of decks or fraction thereof, the RI remains constant as players take cards, while the running count may change. You have already done the math to calculate RI, so when it is your turn all you have to do is the comparison of the current RC to RI.

True count may have an advantage over running index when you have to make multiple decisions in the same hand and the running count doesn't change enough to have to recalculate TC, but these situations are relatively rare.

The RI can help to quantify situations that experienced players know instinctively whether to calculate accurately or to approximate, such as whether to insure. If you have an 8 deck shoe with a 2 deck cut, the running index for insuring (assuming the index is 3) varies linearly from 24 at the start of the shoe to 6 at the end of the shoe, and is easily recalculated as the shoe progresses.

Thoughts?

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If it aint broke don't fix it.

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Originally Posted by Meistro123
If it aint broke don't fix it.
We should encourage people who joined in 2011 and only spoke up five times.

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This is also detailed in Arnold Snyder's book....

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So do you have to redo all the departure indices then?

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Yes, this works, HOWEVER, if you're betting based on TC you still have to convert to TC.

I have done this, however, when I'm close to an index for a play decision.

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Originally Posted by dalehope

Thoughts?
Both methods will produce very similar results. It depends if you like to do multiplications or divisions.

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## That was my intent in bringing this up.

Originally Posted by BJGenius007
Both methods will produce very similar results. It depends if you like to do multiplications or divisions.
My apologies to Arnold - I scanned BJA3 and Blackjack for Blood since I use AOII to see if this this topic was mentioned, but didn't look at Black Belt in Blackjack.

I don't mean to suggest we ignore TC, but we can add another method to our toolbox for counting with less effort and less likelihood of being noticed when it is beneficial.

I originally starting thinking about this as I was replying to a newbie on Green Chip (which I no longer subscribe to) who got backed off for being so slow to make play decisions. It occurred to me that he might be slow due to the effort required to do the divisions, particularly if you have a fractional number of decks remaining. RI should be faster in most computations involving fractional decks.

At the same time, I was laying out a decision tree for the play of the hand, and that was when I realized that some of the decisions could be done more quickly with multiplication, and that the multiplication results may remain valid for successive decisions.

It is all about speed and not appearing to be counting or calculating.

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Originally Posted by cuts you up
So do you have to redo all the departure indices then?
No you would essentially do the math backwards. You have a index number that you multiply by the number of half decks and that gives you a running count limit. If your running count is higher than this limit than you take the index.

This is literally in Black belt in Blackjack.

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Originally Posted by Obi-wan21
This is also detailed in Arnold Snyder's book....

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