hellerbarde

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

ipbastola

JQ to filter JSON by value

Syntax: cat <filename> | jq -c '.[] | select( .<key> | contains("<value>"))'

Example: To get json record having _id equal 611

cat my.json | jq -c '.[] | select( ._id | contains(611))'

Remember: if JSON value has no double quotes (eg. for numeric) to do not supply in filter i.e. in contains(611)

fabiomaggio

1. Clone project

2. Checkout all branches that contain the files that should be moved

3. Delete the remote

4. Run the filter-branch command:

   git filter-branch --tree-filter 'mkdir -p /path/to/tmp; mv * /path/to/tmp; mkdir subdir; mv /path/to/tmp/* subdir/' --tag-name-filter cat --prune-empty -- --all

   • All files are first copied to a temporary dir and move from there to the new destination

• Existing tags are updated