Fixed precision of math.acosh() and math.atanh()

Author: otethal

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/MathModuleBuiltins.java

@@ -1456,13 +1456,20 @@ public double count(double value) {
     @GenerateNodeFactory
     public abstract static class AcoshNode extends MathDoubleUnaryBuiltinNode {
 
+        private static final double TWO_POW_P28 = 0x1.0p28;
+        private static final double LN_2 = 6.93147180559945286227e-01;
+
         @Specialization
         @TruffleBoundary
         @Override
         public double doPI(PInt value) {
             BigInteger bValue = value.getValue();
             checkMathDomainError(bValue.compareTo(BigInteger.ONE) < 0);
 
+            if (bValue.bitLength() >= 28) {
+                return Math.log(bValue.doubleValue()) + LN_2;
+            }
+
             BigDecimal sqrt = SqrtNode.sqrtBigNumber(bValue.multiply(bValue).subtract(BigInteger.ONE));
             BigDecimal bd = new BigDecimal(bValue);
             return Math.log(bd.add(sqrt).doubleValue());
@@ -1471,6 +1478,13 @@ public double doPI(PInt value) {
         @Override
         public double count(double value) {
             checkMathDomainError(value < 1);
+            if (value >= TWO_POW_P28) {
+                return Math.log(value) + LN_2;
+            }
+            if (value <= 2.0) {
+                double t = value - 1.0;
+                return Math.log1p(t + Math.sqrt(2.0 * t + t * t));
+            }
             return Math.log(value + Math.sqrt(value * value - 1.0));
         }
     }
@@ -1564,13 +1578,23 @@ public double count(double value) {
     @GenerateNodeFactory
     public abstract static class AtanhNode extends MathDoubleUnaryBuiltinNode {
 
+        private static final double TWO_POW_M28 = 0x1.0p-28;
+
         @Override
         public double count(double value) {
-            if (value == 0) {
-                return 0;
+            double abs = Math.abs(value);
+            checkMathDomainError(abs >= 1.0);
+            if (abs < TWO_POW_M28) {
+                return value;
+            }
+            double t;
+            if (abs < 0.5) {
+                t = abs + abs;
+                t = 0.5 * Math.log1p(t + t * abs / (1.0 - abs));
+            } else {
+                t = 0.5 * Math.log1p((abs + abs) / (1.0 - abs));
             }
-            checkMathDomainError(value <= -1 || value >= 1);
-            return Math.log((1 / value + 1) / (1 / value - 1)) / 2;
+            return Math.copySign(t, value);
         }
     }