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digitalmars.D.ldc - Why LDC drop d_with_sum code? (windows)

reply KnightMare <black80 bk.ru> writes:
https://forum.dlang.org/post/zpqkgldjlozfnmsveqkn forum.dlang.org

DMD & LDC change d_with_sum(...) to "return .0"
why?

PS I use LDC most time so asking here not in DMD
May 28 2019
parent reply Dennis <dkorpel gmail.com> writes:
On Tuesday, 28 May 2019 at 10:43:38 UTC, KnightMare wrote:
 DMD & LDC change d_with_sum(...) to "return .0"
 why?
Because you are summing an empty array. ``` double d_with_sum(double[] values) safe pure nothrow { import std.algorithm : sum; double[] squares; squares[] = values[] * values[]; return squares.sum; } ``` `squares` is initialized with length and pointer 0, and the values[] * values[] gets truncated to the size of the destination memory, so it becomes a no-op.
May 28 2019
parent KnightMare <black80 bk.ru> writes:
 DMD & LDC change d_with_sum(...) to "return .0"
 why?
Because you are summing an empty array. `squares` is initialized with length and pointer 0, and the values[] * values[] gets truncated to the size of the destination memory, so it becomes a no-op.
yep. thx. C:\content\downloadz\dlang>times2.exe t1=42 ms, 929 ╬╝s, and 1 hnsec r=109226661546_74544967680 t2=42 ms and 578 ╬╝s r=109226661546_74544967680 t3=333 ms, 539 ╬╝s, and 3 hnsecs r=109226661546_66672259072 t4=42 ms, 631 ╬╝s, and 9 hnsecs r=109226661546_74544967680 now I have not small diff but probably double math..
May 28 2019