CHANGELOG.md

@@ -131,7 +131,10 @@
   - `h5rs diff [-r] [-q] [-d D] [-p R] A B [OBJ1 [OBJ2]]` compares objects,
     kinds, datatypes, shapes, attributes, values and link targets; exit
     status 0/1/2 as h5diff's. Every path is compared, including every name
-    of a hard-linked object and the members of a hard-linked group. Objects
+    of a hard-linked object and the members of a hard-linked group; with a
+    `-d`/`-p` tolerance, integers are compared exactly in integer
+    arithmetic (no loss above 2^53), and a `-p` below the f64 epsilon
+    compares exactly, as h5diff's. Objects
     that cannot be compared count as a difference (h5diff exits 0 for them),
     and NaN equals NaN.
   - `h5rs check [--data] FILE` is a structural validator: it walks every

crates/clawhdf5-tools/README.md

@@ -142,6 +142,11 @@ $ h5rs diff -d 0.001 a.h5 b.h5       # |a - b| > 0.001 is a difference
 $ h5rs diff -p 0.01 a.h5 b.h5        # |a - b| / |a| > 1% is a difference
 ```
 
+Integers are compared in integer arithmetic, with or without a tolerance, so
+64-bit values beyond 2^53 lose no precision (`-d 0` tells 2^60 from
+2^60 + 1). A relative tolerance below the f64 epsilon (2.2e-16) compares
+exactly, as h5diff's does.
+
 Exit status: 0 no differences, 1 differences, 2 error — the same as h5diff's
 on the cases `diff_exit_codes_match_h5diff` runs. Compared: which objects
 exist, their kinds, datatypes and shapes, attribute sets and values, dataset

crates/clawhdf5-tools/src/diff.rs

@@ -23,7 +23,8 @@ sets and values, and soft/external link targets.
   -r, --report       list every differing element (position, values, difference)
   -q, --quiet        print nothing; only the exit status
   -d, --delta D      numbers differ only when |a - b| > D
-  -p, --relative R   numbers differ only when |a - b| / |a| > R
+  -p, --relative R   numbers differ only when |a - b| / |a| > R (an R below
+                     the f64 epsilon, 2.2e-16, compares exactly, as h5diff)
   -c, --count N      list at most N differing elements per object with -r
   --max-bytes N      largest dataset read (default 1 GiB); a larger one is an error
 
@@ -119,7 +120,15 @@ pub fn run(args: &mut Args, out: &mut Out) -> std::io::Result<i32> {
                 _ => return args.usage_error(out, "--delta needs a number >= 0", USAGE),
             },
             "-p" | "--relative" => match args.number::<f64>() {
-                Some(r) if r >= 0.0 => opts.tol = Tol::Relative(r),
+                // As h5diff: a relative tolerance below the f64 epsilon
+                // cannot be told from rounding, so it compares exactly.
+                Some(r) if r >= 0.0 => {
+                    opts.tol = if r < f64::EPSILON {
+                        Tol::Exact
+                    } else {
+                        Tol::Relative(r)
+                    }
+                }
                 _ => return args.usage_error(out, "--relative needs a number >= 0", USAGE),
             },
             "-c" | "--count" => match args.number() {
@@ -506,8 +515,9 @@ impl Diff {
                 let pos = format!("[ {} ]", index(i as u64, &dims));
                 let ta = value::text(&va, &|_| None);
                 let tb = value::text(&vb, &|_| None);
-                let dif = match (number(&va), number(&vb)) {
+                let dif = match (int_of(&va), int_of(&vb), number(&va), number(&vb)) {
-                    (Some(x), Some(y)) => value::fmt_float((x - y).abs(), 64),
+                    (Some(x), Some(y), ..) => x.abs_diff(y).to_string(),
+                    (_, _, Some(x), Some(y)) => value::fmt_float((x - y).abs(), 64),
                     _ => String::new(),
                 };
                 rows.push(format!("{pos:<24}{ta:<24}{tb:<24}{dif}"));
@@ -595,12 +605,12 @@ impl Diff {
     }
 
     fn equal(&self, a: &Side, b: &Side, x: &Value, y: &Value) -> bool {
-        if let (Some(p), Some(q)) = (number(x), number(y)) {
+        // Integers in integer arithmetic: through f64 they lose precision
-            let exact_ints = matches!((x, y), (Value::Int(_), Value::Int(_)))
+        // above 2^53, and values that differ would compare equal.
-                || matches!((x, y), (Value::Enum(..), Value::Enum(..)));
+        if let (Some(p), Some(q)) = (int_of(x), int_of(y)) {
-            if exact_ints && matches!(self.opts.tol, Tol::Exact) {
+            return int_close(p, q, self.opts.tol);
-                return int_of(x) == int_of(y);
         }
+        if let (Some(p), Some(q)) = (number(x), number(y)) {
             return close(p, q, self.opts.tol);
         }
         match (x, y) {
@@ -657,6 +667,22 @@ fn close(a: f64, b: f64, tol: Tol) -> bool {
     }
 }
 
+/// `close` for integers, exactly: the difference is taken in i128, so no
+/// precision is lost at any 64-bit magnitude.
+fn int_close(a: i128, b: i128, tol: Tol) -> bool {
+    if a == b {
+        return true;
+    }
+    let d = a.abs_diff(b);
+    match tol {
+        Tol::Exact => false,
+        // d is whole, so d <= t exactly when d <= floor(t) (saturating).
+        Tol::Delta(t) => d <= t.floor() as u128,
+        // d >= 1 here, so the quotient is never rounded to 0.
+        Tol::Relative(r) => a != 0 && d as f64 / a.unsigned_abs() as f64 <= r,
+    }
+}
+
 fn entry_word(e: &Entry) -> &'static str {
     match e {
         Entry::Obj(_, k) => kind_word(*k),
@@ -766,6 +792,26 @@ mod tests {
         assert!(!close(f64::NAN, 1.0, Tol::Delta(1e9)));
     }
 
+    #[test]
+    fn integer_tolerances_are_exact_above_2_pow_53() {
+        let big = 1i128 << 60;
+        assert!(!int_close(big, big + 1, Tol::Delta(0.0)));
+        assert!(!int_close(big, big + 1, Tol::Delta(0.5)));
+        assert!(int_close(big, big + 1, Tol::Delta(1.0)));
+        assert!(!int_close(big, big + 200, Tol::Delta(199.9)));
+        assert!(!int_close(big, big + 1, Tol::Relative(0.0)));
+        assert!(!int_close(big, big + 1, Tol::Relative(1e-19)));
+        assert!(int_close(big, big + 1, Tol::Relative(1e-18)));
+        let umax = i128::from(u64::MAX);
+        assert!(!int_close(umax, umax - 1, Tol::Delta(0.0)));
+        assert!(int_close(
+            i128::from(i64::MIN),
+            umax,
+            Tol::Delta(f64::INFINITY)
+        ));
+        assert!(!int_close(0, 1, Tol::Relative(1e9)));
+    }
+
     #[test]
     fn positions() {
         assert_eq!(index(5, &[3, 4]), "1 1");

crates/clawhdf5-tools/tests/gen_files.py

@@ -126,6 +126,12 @@ for name, last in (("copied.h5", 1), ("copied_changed.h5", 9)):
             g["d"] = np.arange(3)
             g.create_group("s")["e"] = np.array([0, last if gname == "h" else 1])
 
+# 64-bit integers one apart, beyond f64's 2^53 integer precision.
+for name, d in (("big1.h5", 0), ("big2.h5", 1)):
+    with h5py.File(os.path.join(out, name), "w") as f:
+        f["i"] = np.array([2**60 + d, -(2**62) - d], dtype="i8")
+        f["u"] = np.array([2**64 - 1 - d], dtype="u8")
+
 with h5py.File(os.path.join(out, "userblock.h5"), "w", userblock_size=1024) as f:
     f["d"] = np.arange(10)
 

crates/clawhdf5-tools/tests/h5rs_interop.rs

@@ -380,6 +380,38 @@ fn diff_exit_codes_match_h5diff() {
     assert!(s.contains("2 difference(s) found"), "{s}");
 }
 
+/// Tolerances on 64-bit integers one apart, far beyond f64's integer
+/// precision: compared exactly, as h5diff does.
+#[test]
+fn diff_tolerances_compare_large_integers_exactly() {
+    let Some(f) = generate() else { return };
+    let (a, b) = (f.p("big1.h5"), f.p("big2.h5"));
+    let cases: Vec<(Vec<&str>, i32)> = vec![
+        (vec![&a, &b], 1),
+        (vec!["-d", "0", &a, &b], 1),
+        (vec!["-d", "0.5", &a, &b], 1),
+        (vec!["-d", "1", &a, &b], 0),
+        (vec!["-d", "0", &a, &b, "/u"], 1),
+        (vec!["-p", "0", &a, &b], 1),
+        (vec!["-p", "1e-18", &a, &b, "/i"], 1),
+        (vec!["-p", "1e-15", &a, &b], 0),
+    ];
+    let have_h5diff = tool_available("h5diff");
+    for (args, want) in cases {
+        if have_h5diff {
+            assert_eq!(code(&run("h5diff", &args)), want, "h5diff {args:?}");
+        }
+        let o = h5rs(&[&["diff"], args.as_slice()].concat());
+        assert_eq!(code(&o), want, "h5rs diff {args:?}: {}", stdout(&o));
+    }
+    // The reported difference is exact too.
+    let s = stdout(&h5rs(&["diff", "-r", "-d", "0", &a, &b, "/u"]));
+    assert!(
+        s.contains("18446744073709551615    18446744073709551614    1\n"),
+        "{s}"
+    );
+}
+
 /// An object hard-linked under two names is compared under both, with
 /// everything below it, so a file that shares one object between two names
 /// equals a file that stores two identical copies.