refactor: use proper lasti formula for 3.11

[P403n1x87]

Description of the Change

Use the more correct expression for computing the lasti index with Python 3.11.

Alternate Designs

N. A.

Regressions

None. We expect compiler optimisations to do a good job with divisions by powers of 2.

Verification Process

Existing test suite

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.20 🎉

Comparison is base (fbec16f) 69.34% compared to head (0b864e7) 69.55%.

Additional details and impacted files

@@            Coverage Diff             @@
##            devel     #178      +/-   ##
==========================================
+ Coverage   69.34%   69.55%   +0.20%     
==========================================
  Files          25       25              
  Lines        2473     2473              
  Branches      730      730              
==========================================
+ Hits         1715     1720       +5     
+ Misses        420      419       -1     
+ Partials      338      334       -4     

Impacted Files	Coverage Δ
src/py_thread.c	74.08% <100.00%> (-1.03%)	⬇️

... and 4 files with indirect coverage changes

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[github-actions]

Austin Benchmarks

Running Austin benchmarks with Python 3.10.11

Wall time [sampling interval: 1]

Wall time [sampling interval: 1]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	90000 ± 6000	1 ± 0	1.9e-05 ± 6e-06	18 ± 1
3.5.0	86000 ± 6000	1 ± 0	1.1e-05 ± 5e-06	18 ± 2
dev	88000 ± 4000	1 ± 0	1.5e-05 ± 7e-06	17.6 ± 0.8

Wall time [sampling interval: 10]

Wall time [sampling interval: 10]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	83000 ± 10000	0.79 ± 0.05	4e-05 ± 0.0001	19 ± 2
3.5.0	87000 ± 7000	0.77 ± 0.04	1.3e-05 ± 7e-06	18 ± 2
dev	87000 ± 4000	0.73 ± 0.02	1.5e-05 ± 8e-06	17.8 ± 0.8

Wall time [sampling interval: 100]

Wall time [sampling interval: 100]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	9900 ± 300	0.0041 ± 0.0008	5e-05 ± 7e-05	20.6 ± 0.7
3.5.0	9700 ± 200	0.005 ± 0.001	3e-05 ± 3e-05	20.3 ± 0.8
dev	9900 ± 100	0.0034 ± 0.0007	7e-05 ± 4e-05	19.9 ± 0.6

Wall time [sampling interval: 1000]

Wall time [sampling interval: 1000]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	1760 ± 20	0.0003 ± 0.0004	0.0001 ± 0.0001	33 ± 2
3.5.0	1770 ± 20	0.0004 ± 0.0002	3e-05 ± 9e-05	33 ± 2
dev	1760 ± 20	0.0004 ± 0.0004	0 ± 0	33 ± 2

CPU time [sampling interval: 1]

CPU time [sampling interval: 1]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	38000 ± 2000	1 ± 0	2e-05 ± 2e-05	32 ± 2
3.5.0	36000 ± 3000	1 ± 0	2e-05 ± 2e-05	32 ± 2
dev	38000 ± 3000	1 ± 0	3e-05 ± 1e-05	32 ± 1

CPU time [sampling interval: 10]

CPU time [sampling interval: 10]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	38000 ± 5000	1 ± 0	2e-05 ± 2e-05	32 ± 3
3.5.0	39000 ± 1000	1 ± 0	2e-05 ± 1e-05	31.1 ± 0.9
dev	39000 ± 3000	1 ± 0	2e-05 ± 2e-05	31 ± 2

CPU time [sampling interval: 100]

CPU time [sampling interval: 100]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	4700 ± 100	0.013 ± 0.003	0.0001 ± 7e-05	37 ± 2
3.5.0	4600 ± 100	0.012 ± 0.001	8e-05 ± 4e-05	36 ± 2
dev	4800 ± 300	0.012 ± 0.002	0.0001 ± 8e-05	36 ± 1

CPU time [sampling interval: 1000]

CPU time [sampling interval: 1000]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	903 ± 3	0.0013 ± 0.001	0.0002 ± 0.0003	60 ± 3
3.5.0	902 ± 6	0.0009 ± 0.0008	0.0002 ± 0.0003	59 ± 3
dev	904 ± 7	0.0005 ± 0.0007	0.0003 ± 0.0003	58 ± 3

RSA keygen [sampling interval: 1]

RSA keygen [sampling interval: 1]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	28000 ± 2000	1 ± 0	0.0002 ± 0.0002	35 ± 2
3.5.0	29000 ± 2000	1 ± 0	0.00013 ± 8e-05	34 ± 3
dev	28000 ± 2000	1 ± 0	0.0002 ± 0.0002	34 ± 2

RSA keygen [sampling interval: 10]

RSA keygen [sampling interval: 10]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	28500 ± 500	1 ± 0	0.0003 ± 0.0003	34.3 ± 0.7
3.5.0	28000 ± 2000	1 ± 0	0.0002 ± 0.0001	35 ± 2
dev	28300 ± 600	0.9999 ± 0.0002	0.0003 ± 0.0002	34.6 ± 1.0

RSA keygen [sampling interval: 100]

RSA keygen [sampling interval: 100]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	6080 ± 80	0.028 ± 0.009	0.0005 ± 0.0004	44 ± 2
3.5.0	6000 ± 100	0.02 ± 0.01	0.0005 ± 0.0008	43 ± 5
dev	6000 ± 100	0.03 ± 0.02	0.0005 ± 0.0004	44 ± 6

RSA keygen [sampling interval: 1000]

RSA keygen [sampling interval: 1000]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	897 ± 6	0 ± 0	0.001 ± 0.002	72 ± 5
3.5.0	902 ± 3	0.0 ± 0.002	0.001 ± 0.002	72 ± 5
dev	899 ± 3	0 ± 0	0.001 ± 0.001	68 ± 3

Full metrics [sampling interval: 1]

Full metrics [sampling interval: 1]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	37000 ± 2000	1 ± 0	6e-05 ± 3e-05	42 ± 2
3.5.0	36000 ± 1000	1 ± 0	4e-05 ± 2e-05	43 ± 2
dev	36000 ± 2000	1 ± 0	4.2e-05 ± 8e-06	42 ± 2

Full metrics [sampling interval: 10]

Full metrics [sampling interval: 10]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	36000 ± 2000	1 ± 0	4e-05 ± 2e-05	42 ± 2
3.5.0	36000 ± 3000	1 ± 0	4e-05 ± 1e-05	43 ± 3
dev	38000 ± 900	1 ± 0	4e-05 ± 2e-05	40 ± 1

Full metrics [sampling interval: 100]

Full metrics [sampling interval: 100]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	8400 ± 200	0.035 ± 0.005	9e-05 ± 4e-05	56 ± 2
3.5.0	8300 ± 300	0.036 ± 0.004	8e-05 ± 6e-05	58 ± 4
dev	8400 ± 200	0.037 ± 0.004	9e-05 ± 7e-05	59 ± 3

Full metrics [sampling interval: 1000]

Full metrics [sampling interval: 1000]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	1760 ± 30	0.0011 ± 0.0009	0.0001 ± 0.0001	77 ± 4
3.5.0	1770 ± 30	0.0008 ± 0.0005	0.0001 ± 0.0001	75 ± 3
dev	1770 ± 20	0.001 ± 0.0008	0.0001 ± 0.0001	76 ± 3

Multiprocess wall time [sampling interval: 1]

Multiprocess wall time [sampling interval: 1]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	1500 ± 100	1 ± 0	0.0004 ± 0.0004	430 ± 30
3.5.0	2100 ± 100	1 ± 0	0.00018 ± 6e-05	450 ± 30
dev	2100 ± 100	1 ± 0	0.00017 ± 4e-05	450 ± 30

Multiprocess wall time [sampling interval: 10]

Multiprocess wall time [sampling interval: 10]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	1500 ± 100	1 ± 0	0.0004 ± 0.0005	410 ± 20
3.5.0	2100 ± 100	1 ± 0	0.0003 ± 0.0002	450 ± 20
dev	2100 ± 100	1 ± 0	0.0003 ± 0.0004	460 ± 30

Multiprocess wall time [sampling interval: 100]

Multiprocess wall time [sampling interval: 100]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	1500 ± 200	0.06 ± 0.03	0.00015 ± 6e-05	420 ± 20
3.5.0	2000 ± 100	0.08 ± 0.03	0.0001 ± 3e-05	470 ± 30
dev	2100 ± 200	0.08 ± 0.03	0.0001 ± 6e-05	460 ± 40

Multiprocess wall time [sampling interval: 1000]

Multiprocess wall time [sampling interval: 1000]

	Sample Rate	Saturation	Error Rate	Sampling Speed
3.4.1	1300 ± 100	0.03 ± 0.02	4e-05 ± 4e-05	220 ± 90
3.5.0	1850 ± 100	0.036 ± 0.009	7e-05 ± 6e-05	250 ± 50
dev	1900 ± 100	0.02 ± 0.01	4e-05 ± 4e-05	190 ± 80

Benchmark Summary

Comparison of dev against 3.5.0.

The following scenarios show a statistically significant difference in performance between the two versions.

	Sample Rate	Saturation	Error Rate	Sampling Speed
Wall time [sampling interval: 10]	🟡	🟢	🟡	🟡
Wall time [sampling interval: 100]	🟡	🟢	🟡	🟡
RSA keygen [sampling interval: 1000]	🔴	🟡	🟡	🟡
Multiprocess wall time [sampling interval: 1000]	🟡	🟢	🟡	🟢