Good on you to point to the SpecialCombinations page, but you are in the
wrong section. In earlier J in-place operations were performed only on
specific forms using assignment, but now in-place execution is used all
over and the section you mentioned is the only remaining vestige of an
operation that requires a specific form.
The current state of things is described at
https://code.jsoftware.com/wiki/Vocabulary/SpecialCombinations#Execution_In_Place_.28EIP.29
Execution in place reduces cache footprint and runs faster.
Henry Rich
On 10/25/2020 8:41 AM, Jan-Pieter Jacobs wrote:
I guess this is worth mentioning here:
https://code.jsoftware.com/wiki/Vocabulary/SpecialCombinations#Assignments_In_Place_.28AIP.29
Assignments are done in place if you use a specific form recognised by the
interpreter.
If you do not assign the result, or use it in a longer sentence, it will
not be recognised, copying over the entire array, rather than updating a
single element.
Best regards,
Jan-Pieter
On Sun, Oct 25, 2020, 11:56 Hauke Rehr <[email protected]> wrote:
I’d expect it’s allocation and copying.
And as you execute it in the repl, there’s no compiler involved.
Rather, the JE “knows” it’s dealing with a single element only.
Am 25.10.20 um 11:52 schrieb pietdion:
Ok. Thanks.
What explains the huge time difference?
Does the compiler somehow “know” it’s only dealing with one element in
the in place assignment?
On 25 Oct 2020, at 7:25 pm, Lippu Esa <[email protected]> wrote:
Hello
It is not expensive if an in place assignment can be made:
a=.i.1e7
ts '(_999+1000{a) 1000 }a'
0.07655064 134219392
ts 'a=.(_999+1000{a) 1000 }a'
0.00000177 1792
Esa
-----Original Message-----
From: Programming <[email protected]> On Behalf
Of pietdion
Sent: Sunday, October 25, 2020 9:58 AM
To: Programming forum <[email protected]>
Subject: [Jprogramming] Adding constant to a specified element of a
vector
What is the best way to add, say, scalar x to component i of vector y?
One way is (x + i{y) i} y
But this seems clumsy/expensive.
Is there a cleaner/more efficient way?
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