Re: [boost] [Math] float16 on ARM

John Maddock wrote:

The intention of was to provide a *portable* set of typedefs such that each is mapped to the corresponding IEEE defined type.

And indeed, if numeric_limits::is_iec559 happens to be false, then the header will trigger a static_assert and complain that it's incorrectly configured.

So... we could provide a float16_t typedef, but if we're being consistent (and we should be), then it would only be for IEEE float16 compatible types.

My concern is quite how we detect/configure/test that.

#if (__ARM_FP & 2) && defined(__ARM_FP16_FORMAT_IEEE) using float16_t = __fp16; struct std::numeric_limits { const bool is_iec559 = true; etc. etc. }; #endif I think the difficult issues are (a) Do we need a richer vocabulary than floatNN_t to describe the different formats, when more than one is supported at the same time? (b) Can we provide a software fallback for platforms where there is no hardware support? Right now, I'm trying to make a binary file containing these 16-bit floats that will be read (memory-mapped) on an ARM system, built on an x86 system.

I also don't think we currently have any tester running on arm (for example)

I was running ARM64 testers when I had an account with Scaleway, but I don't think anyone was looking at the results; certainly no-one ever asked me anything about them or seemed to notice when I turned them off. I have considered reviving this now that AWS has ARM instances, but their smallest ARM instances are quite a lot larger (and more expensive) than their smallest x86 instances for some reason. That may change eventually. If anyone's interested, get in touch. Regards, Phil.