  # Calculator performance index explained

Calculator performance index is a term coined up by Anton Thimed to be able to compare performance between different calculators.

Basically it performs 20 additions and substractions, 10 multiplications and divisions, 2 square roots, a sine and a logarithm, in total 34 operations. The execution time is measured, and an index is calculated. Please read the full story at www.thimet.de

The performance index is calculated using the following pseudo code:
```For wrapper = 1 to 100

For i = 1 to 10
x = i
x = x + 1
x = x - 4.567E-4
x = x + 70
x = x - 69
x = x * 7
x = x / 11
Next
Rem x should now be 7.636...
x = log(x)
x = sin(x)
x = sqrt(x)
x = sqrt(x)
Rem x should now be 0.3523... in degree mode

Next
```

The outer For...Next loop is optional and is intended to lengthen the total execution time to get a measurable result. The number of loops needed to do this depends on the calculator being benchmarked. For instance, for the TI-92 Plus I used a value of 100. This resulted in a total execution time of ~73 seconds. For the TI-59, the outer loop was not needed because one iteration of the i loop took ~13 seconds.

To calculate the performance index, use this equation:
```index = number_of_operations / execution_time
```

Because we perform 34 operation per loop, the number_of_operations is 34 × wrapper. execution_time is measured in seconds.

Please note that performance can change dramatically depending on the settings of the calculator. For instance, the HP-49G has a listed performance index of 136 when using long integers for calculations. When switching to floating point numbers, the index falls to as little as 13. The index listed on this site is the highest value I was able to achieve, not necessary the highest possible.

Performance index values on this site are comparable to the original ones at www.thimet.de