How to release the space took up by specify variable

Question

Actually relate my this post.But I don't want to clear all memory took up by Mathematica.

memory:=Row[{"Memory Used:",MemoryInUse[]/1024^2.," MB"}]
memory
(* Memory Used:109.582 MB *)

a=RandomInteger[1,{10^8}];
memory
(* Memory Used:871.666 MB *)

b=RandomInteger[1,{10^8}];
memory
(* Memory Used:1634.61 MB *)

I want to clear the variable a and release the space took up by variable a but keep the b. Is possible?

We really need a canonical question for this sort of problem. It's not clear, it's not easy to find in the documentation, it has finer points such as the requirement to delete the Out cells and make sure they're not anywhere in the DownValues for Out either. I say, this should stay open. — LLlAMnYP, Jun 22 '17 at 06:03

Carl Woll · Accepted Answer · 2017-06-20T22:35:40.500

4

Using $HistoryLength = 0 and Clear[a] works for me:

$HistoryLength = 0;
memory:=Row[{"Memory Used:",MemoryInUse[]/1024^2.," MB"}]
memory

a=RandomInteger[1,{10^8}];
memory

b=RandomInteger[1,{10^8}];
memory

Clear[a];
memory

Memory Used:227.932 MB

Memory Used:990.87 MB

Memory Used:1753.81 MB

Memory Used:990.868 MB

edited Jun 20 '17 at 22:35

answered Jun 20 '17 at 21:22

Carl Woll

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Oh,I have misunderstand it before.Thanks a lot.. – yode Jun 20 '17 at 21:47
a = RandomInteger[1, {10^8}]; (* <-- this is In[136] *) Clear[a]; Unprotect[Out]; Out[136] =.; Protect[Out]; is also a working approach. – LLlAMnYP Jun 21 '17 at 13:36

How to release the space took up by specify variable

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