Reset the fp precision before synthesis

The precision is stored statically. Before this PR, the precision of theta is 1000
on the first call and something else on subsequent calls.

This PR resets it to its initial value before starting synthesis.

Author: jlapeyre

src/common.rs

@@ -7,7 +7,13 @@ use dashu_int::IBig;
 use once_cell::sync::Lazy;
 use std::sync::atomic::{AtomicUsize, Ordering};
 
-pub static PREC_BITS: AtomicUsize = AtomicUsize::new(1000);
+const PREC_BITS_INITIAL: usize = 1000;
+pub static PREC_BITS: AtomicUsize = AtomicUsize::new(PREC_BITS_INITIAL);
+
+// Reset precision to the initial value
+pub fn reset_prec_bits() {
+    PREC_BITS.store(PREC_BITS_INITIAL, Ordering::Relaxed);
+}
 
 pub fn set_prec_bits(bits: usize) {
     PREC_BITS.store(bits, Ordering::Relaxed);

src/config.rs

@@ -1,5 +1,5 @@
 use crate::common::ib_to_bf_prec;
-use crate::common::set_prec_bits;
+use crate::common::{reset_prec_bits, set_prec_bits};
 use dashu_float::round::mode::HalfEven;
 use dashu_float::FBig;
 use dashu_int::{IBig, UBig};
@@ -77,6 +77,12 @@ pub fn config_from_theta_epsilon(
     verbose: bool,
 ) -> GridSynthConfig {
     let (theta_num, theta_den) = parse_decimal_with_exponent(&theta.to_string()).unwrap();
+
+    // The desired floating precision is initialized in module common.
+    // It has the initial value the first time this function is called.
+    // But, on subsequent calls, the precision has changed.
+    // We reset it so that the precison is the same at the beginning of every synthesis.
+    reset_prec_bits();
     let theta = ib_to_bf_prec(theta_num) / ib_to_bf_prec(theta_den);
     let (epsilon_num, epsilon_den) = parse_decimal_with_exponent(&epsilon.to_string()).unwrap();
     // The magic number 12 safely overapproximates the bits of precision.