Unreleased Restricted Stock Units (in thousands)
Weighted average grant date fair value per share
Unvested restricted stock at January 31, 2018
5,670.7
$82.94
Granted
2,250.7
144.37
Vested
(2,982.0)
76.30
Canceled/Forfeited
(681.9)
94.70
Performance Adjustment (1)
29.9
101.74
Unvested restricted stock at January 31, 2019
4,287.4
$120.07
restricted stock units : .
a summary of restricted stock activity for the fiscal year ended january 31 2019 is as follows : .
-1 based on autodesk ' s financial results and relative total stockholder return for the fiscal 2018 performance period .
the performance stock units were attained at rates ranging from 90 .
0 % to 117 .
6 % of the target award .
for the restricted stock granted during fiscal years ended january 31 2019 2018 and 2017 the weighted average grant date fair values were $ 144 .
37 $ 106 .
55 and $ 65 .
95 respectively .
the fair values of the shares vested during fiscal years ended january 31 2019 2018 and 2017 were $ 425 .
4 million $ 399 .
7 million and $ 232 .
2 million respectively .
during the fiscal year ended january 31 2019 autodesk granted 2 .
1 million restricted stock units .
restricted stock units vest over periods ranging from immediately upon grant to a pre-determined date that is typically within three years from the date of grant .
restricted stock units are not considered outstanding stock at the time of grant as the holders of these units are not entitled to any of the rights of a stockholder including voting rights .
the fair value of the restricted stock units is expensed ratably over the vesting period .
autodesk recorded stock-based compensation expense related to restricted stock units of $ 189 .
3 million $ 202 .
1 million and $ 173 .
0 million during fiscal years ended january 31 2019 2018 and 2017 respectively .
as of january 31 2019 total compensation cost not yet recognized of $ 364 .
5 million related to non-vested awards is expected to be recognized over a weighted average period of 1 .
76 years .
at january 31 2019 the number of restricted stock units granted but unvested was 3 .
9 million .
during the fiscal year ended january 31 2019 autodesk granted 0 .
2 million performance stock units for which the ultimate number of shares earned is determined based on the achievement of performance criteria at the end of the stated service and performance period .
the performance criteria for the performance stock units are based on annualized recurring revenue - " arr " and free cash flow per share goals adopted by the compensation and human resources committee as well as total stockholder return compared against companies in the s & p computer software select index or the s & p north american technology software index - " relative tsr " .
these performance stock units vest over a three-year period and have the following vesting schedule : .

Question: What is the performance criteria for the performance stock units?
Answer: The performance criteria for the performance stock units are based on Annualized Recurring Revenue ("ARR") and free cash flow per share goals adopted by the Compensation and Human Resources Committee, as well as total stockholder return compared against companies in the S&P Computer Software Select Index or the S&P North American Technology Software Index ("Relative TSR").