Remove code for fast_float(old=True)

[mkoeppe]

The old code was replaced by new code in 2009 and is unused in the library.

$ git grep 'fast_float *(.*old *='
src/sage/ext/fast_eval.pyx:    sage: f = fast_float(sqrt(x^7+1), 'x', old=True)
src/sage/ext/fast_eval.pyx:def fast_float(f, *vars, old=None, expect_one_var=False):
src/sage/rings/polynomial/multi_polynomial.pyx:            sage: list(fast_float(K(0), old=True))
src/sage/rings/polynomial/multi_polynomial.pyx:            sage: list(fast_float(K(17), old=True))
src/sage/rings/polynomial/multi_polynomial.pyx:            sage: list(fast_float(y, old=True))

Given that this is from a time before deprecation warnings were invented, and this is clearly marked as old, we just remove this code.

We also replace the remaining direct uses of _fast_float_ methods by:

• sage.calculus.integration.numerical_integral
• sage.numerical.optimize.{minimize_constrained,find_fit}
• Expression.find_local_minimum
• Expression.find_root

Finally, we remove the entire implementation of the old fast_float (centering around class FastDoubleFunc) and all _fast_float_ methods.

CC: @fchapoton @mjungmath @egourgoulhon @videlec @mwageringel @kcrisman @slel @nbruin

Component: fast_callable

Author: Matthias Koeppe, Michael Orlitzky

Branch/Commit: 6fc96d6

Reviewer: Michael Orlitzky, Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/32234

[mkoeppe]

Description changed:

--- 
+++ 
@@ -8,3 +8,6 @@
 src/sage/rings/polynomial/multi_polynomial.pyx:            sage: list(fast_float(K(17), old=True))
 src/sage/rings/polynomial/multi_polynomial.pyx:            sage: list(fast_float(y, old=True))
 ```
+
+Given that this is from a time before deprecation warnings were invented, and this is clearly marked as old, we just remove this code.
+

[mkoeppe]

Description changed:

--- 
+++ 
@@ -11,3 +11,8 @@
 
 Given that this is from a time before deprecation warnings were invented, and this is clearly marked as old, we just remove this code.
 
+We cannot quite remove the `_fast_float_` methods, on the other hand; they are still used directly by:
+- `sage.calculus.integration.numerical_integral`
+- `sage.numerical.optimize.{minimize_constrained,find_fit}
+- `Expression.find_local_minimum`
+

[mkoeppe]

Description changed:

--- 
+++ 
@@ -13,6 +13,6 @@
 
 We cannot quite remove the `_fast_float_` methods, on the other hand; they are still used directly by:
 - `sage.calculus.integration.numerical_integral`
-- `sage.numerical.optimize.{minimize_constrained,find_fit}
+- `sage.numerical.optimize.{minimize_constrained,find_fit}`
 - `Expression.find_local_minimum`
 

[mkoeppe]

comment:4

Cc'ing the last person who modified numerical_integral...

[mkoeppe]

Branch: u/mkoeppe/remove_code_for_fast_float_old_true_

[orlitzky]

comment:7

Needs review, or are you waiting to see if the three uses of _fast_float_ can be removed?

[orlitzky]

Commit: d900e6e

[mkoeppe]

Author: Matthias Koeppe

[mkoeppe]

comment:8

I was kind of hoping that we can get rid of these _fast_float_-using methods, but we can of course do that later

[orlitzky]

comment:9

It's unfortunate that there is a _fast_callable_ method on symbolic expressions that seems to do something else entirely... but this appears to be all that is necessary to update find_local_minimum():

diff --git a/src/sage/symbolic/expression.pyx b/src/sage/symbolic/expression.pyx
index 0e8dc117bc..fbe74582c2 100644
--- a/src/sage/symbolic/expression.pyx
+++ b/src/sage/symbolic/expression.pyx
@@ -12173,11 +12173,13 @@ cdef class Expression(CommutativeRingElement):
         - William Stein (2007-12-07)
         """
         from sage.numerical.optimize import find_local_minimum
+        from sage.ext.fast_callable import fast_callable

         if var is None:
             var = self.default_variable()
-        return find_local_minimum(self._fast_float_(var),
-                                        a=a, b=b, tol=tol, maxfun=maxfun )
+
+        f = fast_callable(self, vars=[var])
+        return find_local_minimum(f, a=a, b=b, tol=tol, maxfun=maxfun)

     ###################
     # Fast Evaluation #

[orlitzky]

comment:10

Numerical integration:

diff --git a/src/sage/calculus/integration.pyx b/src/sage/calculus/integration.$
index 93a3681854..6dd4195b2d 100644
--- a/src/sage/calculus/integration.pyx
+++ b/src/sage/calculus/integration.pyx
@@ -316,7 +316,8 @@ def numerical_integral(func, a, b=None,
                 else:
                    if ell.is_numeric() and not ell.is_zero():
                       raise ValueError('integral does not converge at infinity$
-            func = func._fast_float_(v)
+            func = fast_callable(func, vars=[v])
+

     if isinstance(func, FastDoubleFunc):
         F.function = c_ff

[nbruin]

comment:11

Replying to @orlitzky:

It's unfortunate that there is a _fast_callable_ method on symbolic expressions that seems to do something else entirely

Possibly the name is unfortunate, but the presence of the method is actually what makes fast_callable work. Given that it implements the protocol that makes fast_callable work, I think the name is actually quite understandable.

[orlitzky]

comment:12

I've updated the three files mentioned in the description. The doctests in those files pass but I haven't run the full suite yet.

[orlitzky]

Changed author from Matthias Koeppe to Matthias Koeppe, Michael Orlitzky

[orlitzky]

Changed branch from u/mkoeppe/remove_code_for_fast_float_old_true_ to u/mjo/ticket/32234