Fix size_t -> int -> size_t round trip in Cycles

There are two things achieved by this change:

- No possible downcast of size_t to int when calculating motion steps.
- Disambiguate call to `min()` which was for some reason considered
  ambiguous on 32bit platforms `min(int, unsigned int)`.
- Do the same for the `max()` call to keep them symmetrical.

On an implementation side the `min()` is defined for a fixed width
integer type to disambiguate uint from size_t on 32bit platforms,
and yet be able to use it for 32bit operands on 64bit platforms without
upcast.

This ended up in a bit bigger change as the conditional compile-in of
functions is easiest if the functions is templated. Making the functions
templated required to remove the other source of ambiguity which is
`algorithm.h` which was pulling min/max from std.

Now it is the `math.h` which is the source of truth for min/max.
It was only one place which was relying on `algorithm.h` for these
functions, hence the choice of `math.h` as the safest and least
intrusive.

Fixes 32bit platforms (such as i386) in Debian package build system.

Differential Revision: https://developer.blender.org/D14062

1 files changed, 1 insertions, 1 deletions

diff --git a/intern/cycles/device/device.cpp b/intern/cycles/device/device.cpp
index 14c97affb76..4d981e45ff1 100644
--- a/intern/cycles/device/device.cpp
+++ b/intern/cycles/device/device.cpp
@@ -335,7 +335,7 @@ DeviceInfo Device::get_multi_device(const vector<DeviceInfo> &subdevices,
     if (device.type == DEVICE_CPU && subdevices.size() > 1) {
       if (background) {
         int orig_cpu_threads = (threads) ? threads : TaskScheduler::max_concurrency();
-        int cpu_threads = max(orig_cpu_threads - (subdevices.size() - 1), 0);
+        int cpu_threads = max(orig_cpu_threads - (subdevices.size() - 1), size_t(0));
 
         VLOG(1) << "CPU render threads reduced from " << orig_cpu_threads << " to " << cpu_threads
                 << ", to dedicate to GPU.";