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How to evaluate parallelized with @@@?

Zhenyu Zeng
Posted 3 years ago

Hello, I am curious how to evaluate parallelized with @@@. For example:

a = RandomInteger[9, {10000000, 3}]
b = ReplaceAll[0 -> 1][a]
c=(Total[{#1 + #2, #2*#3, #3/#1}]) & @@@ b

This is just a case. In many situations, I need to save time when evaluating them with @@@, so I hope to use parallelize with @@@, but I can't, as I change to 

Parallelize[Total[{#1 + #2, #2*#3, #3/#1}] & @@@ b]

The error is: enter image description here
POSTED BY: Zhenyu Zeng
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Yes, I can reproduce the problem in 13.1. I am surprised that it does not work in that version. I would report the problem to Wolfram Support and ask if the change is intentional.
POSTED BY: Szabolcs Horvát
Zhenyu Zeng
Zhenyu Zeng
Posted 3 years ago

If you have replies from WL, I hope you can send me a copy. I am weird about why using ParallelMap takes even more than ten times time than not using ParalleleMap?
POSTED BY: Zhenyu Zeng
Hans Milton
Hans Milton
Posted 3 years ago

Zhenyu, the term 'I would' is an idiomatic (proxy) way of saying 'you should'. So I think that Szabolcs is suggesting that you should report this problem to Wolfram.
POSTED BY: Hans Milton
Zhenyu Zeng
Zhenyu Zeng
Posted 3 years ago

Hello, May you tell me why I would is an idiomatic way of saying you should and when I would means I would? Thanks.
POSTED BY: Zhenyu Zeng
Updating Name
Updating Name
Posted 3 years ago

Think of it as a way of saying "If I were you I would ...", different from "I will ...".

If you think that is confusing, consider how confusing it is for someone learning 中文 when they come across 加油 or 老马识途 :-)
POSTED BY: Updating Name
Zhenyu Zeng
Zhenyu Zeng
Posted 3 years ago

Thanks a lot. So, if one says "I would", one exactly says "If ... I would". Am I right? In Chinese, there are a lot of this implied meaning。
POSTED BY: Zhenyu Zeng
Zhenyu Zeng
Zhenyu Zeng
Posted 3 years ago 
In[1]:= $Version

Out[1]= "13.1.0 for Microsoft Windows (64-bit) (June 16, 2022)"
In[3]:= list = RandomInteger[10, {20, 2}]

Out[3]= {{9, 5}, {6, 3}, {7, 5}, {9, 6}, {8, 1}, {4, 8}, {2, 8}, {6, 
  7}, {10, 8}, {3, 9}, {7, 7}, {5, 7}, {7, 7}, {8, 3}, {9, 6}, {8, 
  6}, {8, 4}, {8, 8}, {1, 7}, {1, 2}}

In[4]:= Parallelize[Print @@@ list]

During evaluation of In[4]:= Parallelize::nopar1: Print@@@list cannot be parallelized; proceeding with sequential evaluation.

During evaluation of In[4]:= 95

During evaluation of In[4]:= 63

During evaluation of In[4]:= 75

During evaluation of In[4]:= 96

During evaluation of In[4]:= 81

During evaluation of In[4]:= 48

During evaluation of In[4]:= 28

During evaluation of In[4]:= 67

During evaluation of In[4]:= 108

During evaluation of In[4]:= 39

During evaluation of In[4]:= 77

During evaluation of In[4]:= 57

During evaluation of In[4]:= 77

During evaluation of In[4]:= 83

During evaluation of In[4]:= 96

During evaluation of In[4]:= 86

During evaluation of In[4]:= 84

During evaluation of In[4]:= 88

During evaluation of In[4]:= 17

During evaluation of In[4]:= 12

Out[4]= {Null, Null, Null, Null, Null, Null, Null, Null, Null, Null, \
Null, Null, Null, Null, Null, Null, Null, Null, Null, Null}

Weird, I still can't.

enter image description here
POSTED BY: Zhenyu Zeng
POSTED BY: Szabolcs Horvát
Zhenyu Zeng
Zhenyu Zeng
Posted 3 years ago

ParalllMap is terrible. Don't use it.

b = ReplaceAll[0 -> 1][RandomInteger[9, {100000000, 3}]];
Plus @@ (Total[{#1 + #2, #2*#3, #3/#1}] & @@@ b) // Timing
Plus @@ ParallelMap[Apply[Total[{#1 + #2, #2*#3, #3/#1}] &], 
   b] // Timing

Out are 

{346.641, 4047515637259/1260}
{3845.88, 4047515637259/1260}
POSTED BY: Zhenyu Zeng

Perhaps do something like this:

ParallelMap[Apply[Total[{#1 + #2, #2*#3, #3/#1}] &], b]
POSTED BY: Sander Huisman
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