planner: remove Bühlmann factor cache

The Bühlmann factors were cached in a thread-safe hashmap. It seemed
somewhat dubious that entering a critical section and doing a hash-lookup
would be significantly faster than a simple exp() call.

Indeed, in a very cache friendly test (16 entries, tight loop) calling the
factor() function 32 000 000 times from a different translation units we get:
  - with cache: 604 ms
  - without cache: 266 ms
Therefore, remove the cache. Given that 32 000 000 calls take only 266 ms,
it appears not sensible to try to optimize this function anyway.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

1 files changed, 0 insertions, 2 deletions

diff --git a/core/qthelper.h b/core/qthelper.h
index 4a7d8ec52..0f3dd9c1b 100644
--- a/core/qthelper.h
+++ b/core/qthelper.h
@@ -146,8 +146,6 @@ const char *subsurface_user_agent();
 enum deco_mode decoMode();
 int parse_seabear_header(const char *filename, char **params, int pnr);
 char *get_current_date();
-double cache_value(int tissue, int timestep, enum inertgas gas);
-void cache_insert(int tissue, int timestep, enum inertgas gas, double value);
 void print_qt_versions();
 void lock_planner();
 void unlock_planner();