Introduce a variable to specify the minimum number of calibration measurements

doc/doxygen/chapters/12online_performance_tools.doxy

@@ -389,11 +389,11 @@ parameters through starpu_hash_crc32c_be for instance.
 StarPU will automatically determine when the performance model is calibrated,
 or rather, it will assume the performance model is calibrated until the
 application submits a task for which the performance can not be predicted. For
-::STARPU_HISTORY_BASED, StarPU will require 10 (_STARPU_CALIBRATION_MINIMUM)
+::STARPU_HISTORY_BASED, StarPU will require 10 (STARPU_CALIBRATE_MINIMUM)
 measurements for a given size before estimating that an average can be taken as
 estimation for further executions with the same size. For
 ::STARPU_REGRESSION_BASED and ::STARPU_NL_REGRESSION_BASED, StarPU will require
-10 (_STARPU_CALIBRATION_MINIMUM) measurements, and that the minimum measured
+10 (STARPU_CALIBRATE_MINIMUM) measurements, and that the minimum measured
 data size is smaller than 90% of the maximum measured data size (i.e. the
 measurement interval is large enough for a regression to have a meaning).
 Calibration can also be forced by setting the \ref STARPU_CALIBRATE environment

doc/doxygen/chapters/40environment_variables.doxy

@@ -314,6 +314,14 @@ is the default behaviour.
 Note: this currently only applies to <c>dm</c> and <c>dmda</c> scheduling policies.
 </dd>
 
+<dt>STARPU_CALIBRATE_MINIMUM</dt>
+<dd>
+\anchor STARPU_CALIBRATE_MINIMUM
+\addindex __env__STARPU_CALIBRATE_MINIMUM
+This defines the minimum number of calibration measurements that will be made
+before considering that the performance model is calibrated. The default value is 10.
+</dd>
+
 <dt>STARPU_BUS_CALIBRATE</dt>
 <dd>
 \anchor STARPU_BUS_CALIBRATE

src/starpu_parameters.h

@@ -1,6 +1,6 @@
 /* StarPU --- Runtime system for heterogeneous multicore architectures.
  *
- * Copyright (C) 2011  Université de Bordeaux 1
+ * Copyright (C) 2011, 2014  Université de Bordeaux 1
  *
  * StarPU is free software; you can redistribute it and/or modify
  * it under the terms of the GNU Lesser General Public License as published by
@@ -22,7 +22,7 @@
 
 /* How many executions a codelet will have to be measured before we
  * consider that calibration will provide a value good enough for scheduling */
-#define _STARPU_CALIBRATION_MINIMUM 10
+#define _STARPU_CALIBRATION_MINIMUM ((unsigned) starpu_get_env_number_default("STARPU_CALIBRATE_MINIMUM", 10))
 
 /* Assumed relative performance ratios */
 /* TODO: benchmark a bit instead */