If tuning is off and resource path is available, the current tunecache.tsv will be overwrited

[SaltyChiang]

If QUDA_ENABLE_TUNE=0 and QUDA_RESOURCE_PATH=/some/available/path are set, QUDA will write the tune cache to tunecache.tsv with default parameters after #1531. However, it will overwrite the current cache file even though optimized parameters are already stored in it. I lost some multigrid parameters after trying to debug with some eigensolve functions without enabling autotuning.

Is this behavior by design? I think keeping the current optimized parameters is useful.

[SaltyChiang]

Also, if we enable the autotuning after saving the default parameters, QUDA will directly use them instead of retuning those functions. May be we need a option to control the behavior.

[maddyscientist]

This is a bug I guess, and some good suggestions there for how to proceed @SaltyChiang.

Perhaps if the resource path is set, but tuning is disabled, we use a different file, say tunecache_notune.tsv. Then there would be no interference between a tuning path and a non-tuning path?

[SaltyChiang]

Sounds good for a different file, and should be the easiest way to implement.

[maddyscientist]

Since this was s trivial fix, I've just applied it to #1540.

[SaltyChiang]

@maddyscientist Thanks for the fix, also for the complex.h issue!