From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on ip-172-31-65-14.ec2.internal X-Spam-Level: X-Spam-Status: No, score=-0.0 required=3.0 tests=BAYES_20,FREEMAIL_FROM, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Received: by 2002:ac8:54b:0:b0:3b6:2e5d:9b63 with SMTP id c11-20020ac8054b000000b003b62e5d9b63mr537477qth.192.1674427749852; Sun, 22 Jan 2023 14:49:09 -0800 (PST) X-Received: by 2002:a05:6808:1704:b0:35b:c586:d978 with SMTP id bc4-20020a056808170400b0035bc586d978mr1134266oib.77.1674427749528; Sun, 22 Jan 2023 14:49:09 -0800 (PST) Path: eternal-september.org!reader01.eternal-september.org!news.mixmin.net!proxad.net!feeder1-2.proxad.net!209.85.160.216.MISMATCH!news-out.google.com!nntp.google.com!postnews.google.com!google-groups.googlegroups.com!not-for-mail Newsgroups: comp.lang.ada Date: Sun, 22 Jan 2023 14:49:09 -0800 (PST) In-Reply-To: Injection-Info: google-groups.googlegroups.com; posting-host=157.143.56.236; posting-account=Wbe3fAoAAAALa8UT9MWTy6mw2ahlRJms NNTP-Posting-Host: 157.143.56.236 References: <9c7cccd9-733f-49a8-b482-087ccb14b58dn@googlegroups.com> <3db6b678-5a45-4b4d-9f6c-e4933b04d6c2n@googlegroups.com> User-Agent: G2/1.0 MIME-Version: 1.0 Message-ID: <6dbff95d-8e30-4a60-ad03-d0aa4cff1583n@googlegroups.com> Subject: Re: Real_Arrays on heap with overloaded operators and clean syntax From: Jim Paloander Injection-Date: Sun, 22 Jan 2023 22:49:09 +0000 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Xref: reader01.eternal-september.org comp.lang.ada:64853 List-Id: > > > > Dear ADA lovers,=20 > > > > with stack allocation of Real_Vector ( 1 .. N ) when N >=3D 100,000= I get STACK_OVERFLOW ERROR while trying to check how fast operator overloa= ding is working for an expression=20 > > > >=20 > > > > X :=3D A + B + C + C + A + B, where=20 > > > > A,B,C,X are all Real_Vector ( 1 .. N ).=20 > > > >=20 > > > > So my only option was to allocate on the heap using new. But then I= lost the clean syntax=20 > > > >=20 > > > > X :=3D A + B + C + C + A + B=20 > > > >=20 > > > > and I had to write instead:=20 > > > >=20 > > > > X.all :=3D A.all + B.all + C.all + C.all + A.all + B.all.=20 > > > >=20 > > > > This is really ugly and annoying because when you are using Real_Ar= rays for implementing some linear algebra method who relies heavilly on mat= rix vector products and vector updates, you do need to allocate on the heap= (sizes are determined in runtime) and you do need a clean syntax. So, is t= here any way to simplify my life without using the .all or even without dec= laring A,B,C,X as access Real_Vector?=20 > > > > Thanks for your time!=20 > > > Easiest solution is probably to declare a new task and specify the st= ack size using the Storage_Size aspect. Allocate as much stack space as you= need to be able to do the calculations and do all the allocations on the d= eclared task, not on the environment task. You will avoid the unnecessary h= eap allocations and have nice clean syntax.=20 > > >=20 > > > Best regards,=20 > > > Joakim=20 > > Thank you for your reply,=20 > > since I am a newbie I was under the impression that tasks are used only= when you want to write a parallel code that takes advantage of multicore a= rchitectures. You suggest I have a single task and single thread something = like this? I see, but there should be a way to do this also for the main pr= ogram. But thanks anyway. Are you aware of any libraries similar to Real_Ar= rays, but who allocated memory internally using heap? This is the natural w= ay to do such things. Similarly to the Containers.Vector. But Vector has su= ch an awful syntax. There should be something like an indexer [i] similarly= to the C++ std::vector to make things simpler and overloaded operators sim= ilarly to Real_Arrays. It is a no brainer. Most programs need to allocate o= n the heap, why did they restrict Real_Arrays on the stack? > It my impression that in the Ada community the preferred way of working i= s in general stack only. Heap allocations are avoided for a number of reaso= ns for example performance, the application needs to ask the operating syst= em for memory which one doesn't know how much time that will take nor if it= always will succeed. In addition, applications that use the heap may be su= sceptible to heap memory fragmentation. In Ada, it is easy to specify stack= sizes when declaring tasks. It is not part of the Ada standard to specify = stack size of the environment task. The Ada way is to declare new tasks and= do work on them. Prefer the bounded containers over the unbounded containe= rs. If you really need to allocate objects I recommend using storage pools = with pre-allocated memory also known as arena pools. With great depression I realized that the preferred way is of stack only. T= his is very restrictive excluding all scientific modelling involving solver= s for partial differential equations, linear algebra kernels, etc. It is in= sane. Completely insane. 3D simulations of physical phenomena may involve b= illions of grid-cells and at each grid-cell several unknowns are defined (v= elocity, pressure, temperature, energy, density, etc). That is why they are= using Fortran or C++, but ADA has really cool stuff for so many things, wh= y not vectors and matrices and heap allocation? Would you please give me an= example, I googled and I cannot find a single example demonstrating how to= use a task with the declaration of stack size. Why is there so little info= rmation online about so important things such as allocation?=20